Psychology of Law Unit 1
Chapter 1: An Introduction to Forensic Psychology
- Forensic psychology: a field of psychology that deals with all aspects of human behaviour as it
relates to the law or legal system.
- Although forensic psychologists often carry out the sorts of tasks you see in movies, the way in
which they carry them out is very different from and less glamorous than the typical Hollywood
image. The way in which forensic psychology is portrayed by the media is usually inaccurate.
What is forensic psychology?
- There is no generally accepted definition of the field. Forensic psychology is often referred to as
legal psychology or criminological psychology. Much of the debate about how forensic psych
should be defined centres on whether the definition should be narrow or broad. A narrow
definition would focus on certain aspects of the field while ignoring other, potentially important
aspects (focusing on applied aspects while ignoring the experimental research focus only on
the clinical or experimental aspects). This appears to be how many leading psychologists prefer
to define the discipline. The American Board of Forensic Psychology (ABFP) and the American
Psychology-Law Society (AP-LS), define the field in a narrow fashion. These associations have
defined forensic psych as “the professional practice by psychologists within the areas of clinical
psychology, counseling psychology, neuropsychology, and school psychology, when they are
engaged regularly as experts and represent themselves as such, in an activity primarily intended
to provide professional psychological expertise to the judicial system. Therefore, according to
this definition, any psychologist who provides expertise to the judicial system but happens to
work in an area of psychology outside the scope of their definition, such as social psychology,
would not be doing work in the area of forensic psych.
- In addition, psychologists who do not provide professional expertise to the judicial system on a
regular basis would not be considered a forensic psychologist (even if they worked in
neuropsychology, for example). For these reasons, many psychologists have problems using
narrow definitions to define forensic psych.
- Broad definitions are less restrictive. One definition proposed by Bartol and Bartol (2006) is “(a)
research endeavor that examines aspects of human behaviour directly related to the legal
process..and (b) the professional practice of psychology within, or in consultation with, a legal
system that embraces both civil and criminal law”. The narrow definition focuses solely on the
application of psychology to the legal system while the broad definition does not restrict
forensic psych to applied issues. It also focuses on the research that is required to inform
- Many leading psychologists and the professional association to which they belong, prefer the
narrow definition. Reflecting on the petition made to the American Psychological Association in
2001 to recognize forensic psych as a specialization, Otto and Heilbrun state that “forensic psych
should be defined narrowly, to include the primarily clinical aspects of forensic assessment,
treatment and consultation”. According to this definition the only individuals who should call themselves forensic psychologists are those who engage in clinical practice (assessing, treating,
or consulting) which leaves out those who spend their time conducting forensic-related research
– problems with narrow definitions.
- The textbook adopts a broad definition of forensic psych – forensic psych is an eclectic field and
its research frequently originates in areas not often obviously connected with the forensic area
such as social, cognitive, personality, and developmental psychology.
- No crime-based reality show has been more popular than Cops introduced by Fox network in
The roles of forensic psychologists
- Individuals who are interested in issues that arise at the intersection between psychology and
law. What typically differs across the definitions is the particular focus the forensic psychologist
takes (take on the role of the clinician or researcher). These roles are not mutually exclusive and
one person can take on more than one role. Some forensic psychologists are clinicians,
researchers and legal scholars.
The forensic psychologist as clinician
- Clinical forensic psychologists: are broadly concerned with the assessment and treatment of
mental health issues as they pertain to the law or legal system. This can include both research
and practice in a wide variety of settings (schools, prisons, hospitals). They are often concerned
with the assessment and treatment of persons with mental disorders within the context of the
law. Research side: validation of an assessment tool that has been developed to predict the risk
of an offender being violent. Practical side: assessment of an offender to assist the parole board
in making an accurate determination of whether the offender is likely to pose risk to the
- Other issues they are interested in may include: divorce and child custody mediation,
determinations of criminal responsibility (insanity) and competency to stand trial, providing
expert testimony on questions of a psychological nature, personnel selection (ex. for law
enforcement agencies), conducting critical incident stress debriefings, designing and conducting
treatment programs for offenders.
- A clinical forensic psychologist must be a licensed clinical psychologist who has specialized in the
forensic area. Some form of graduate-level training is always required. In Alberta,
Saskatchewan, NFL and Labrador, NB, NS, the requirement is a master’s degree in psychology,
while in BC, Manitoba, Ontario, PEI, and Quebec, a doctoral degree in psychology is required.
After the completion of the degree there is an intense period of supervised practice in an
applied forensic setting under an experienced clinical supervisor. The last step of the licensing
process is a comprehensive exam, which often involves an oral component.
- Forensic psychiatry: a field of medicine that deals with all aspects of human behaviour as it
relates to the law or legal system. In Canada, clinical forensic psych and forensic psychiatry are
more similar than different. Both are trained to assess and treat individuals experiencing mental
health problems who come into contact with the law and are involved in every component of the criminal justice system. They often engage in similar sorts of research as well (e.g.
developing causal models of violent behaviour). The most obvious difference is that psychiatrists
are medical doctors who can prescribe medication and therefore undergo different training.
- in contrast to a psychiatrist’s general reliance on a medical model of mental illness,
psychologists tend to view mental illness more as a product of an individual’s physiology,
personality and environment.
- Other forensic disciplines often confused with forensic psychology: forensic anthropology –
examine remains of deceased victims to determine key facts about them; forensic linguistics –
examine the spoken and written word to assist criminal investigators; forensic chemistry – study
chemical aspects of crime scenes; forensic ondontology – study dental aspects of criminal
activity which can include identifying deceased victims through dental records; forensic
pathology – examine the remains of dead bodies in attempt to determine the time and cause of
death through physical autopsy; forensic entomology – concerned with how insects can assist
with criminal investigations
The forensic psychologists as researcher
- Role of the experimenter and although it does not have to be separated from the clinical role, it
often is. Experimental forensic psychologists: are broadly concerned with the study of human
behaviour as it relates to the law or legal system. They can be interested in any research issue
that relates to the law or legal system.
- They can be interested in: examining the effectiveness of risk assessment strategies,
determining what factors influence jury decision making, developing and testing better ways to
conduct eyewitness lineups, evaluating offender and victim treatment programs, studying the
impact of questioning style on memory recall, examining the effect of stress management
interventions on police officers.
- They differ from clinical forensic psychologists in what they do and in their training. Those
primarily interested in research will have undergone Ph.D. level training in one of many different
types of experimental graduate programs (no internship usually required). The program will
have a faculty member associated with it who is conducting research in a forensic area. The
graduate research will be focused primarily on a topic related to forensic psychology.
- Is eclectic and requires expertise in areas such as memory processing, decision making,
organizational issues etc. The training is more varied than for clinical.
The forensic psychologist as legal scholar
- Much less common. Much of the focus resulted from the formation of two initiatives at Simon
Fraser University (SFU) in Burnaby, BC. The first of these was SFU’s Psychology and Law
Program, established in 1991. This program has partnered with the University of BC to allow
students to obtain both their Ph.D. in psychology and their L.L.B. in law – forensic psychologists
who are much more informed about legal processes. The second initiative was formed in 1991
as well, the Mental Health, Law, and Policy Institute (MHLPI) at SFU. The purpose of MHLPI is to “promote interdisciplinary collaboration in research and training in areas related to mental
health law and policy.
- According to Brigham, forensic psychologists in their role as legal scholars would most likely
engage in scholarly analyses of mental health law and psychologically oriented legal movements
whereas their applied work would most likely center around policy analysis and legislative
The relationship between psychology and law
- Craig Haney, professor of psychology at the University of Cali, Santa Cruz, suggests there are
three primary ways in which psychology and law can relate to one another. He calls these
relationships psychology and the law, psychology in the law, and psychology of the law.
Clinical and experimental forensic psychologists are involved in the first two areas the most.
Psychology of the law is largely the domain of the legal scholar role.
- Psychology and the law: the use of psychology to examine the operation of the legal system
- Psychology in the law: the use of psychology in the legal system as that system operates
- Psychology of the law: the use of psychology to examine the law itself
Psychology and the law
- Psychology is viewed as a separate discipline to the law, examining and analysing various
components of the law and the legal system from a psychological perspective. Research in this
area usually examines assumptions made by the law or our legal system asking questions like,
“are eyewitnesses accurate?” Forensic psychologists attempt to answer these questions and
communicate their findings to the legal community. Much of forensic psych deals with this
Psychology in the law
- One a body of psychological knowledge exists in any of the above-mentioned areas of study,
that knowledge can be used in the legal system by psychologists, lawyers, judges and others. It
involves the use of psychological knowledge in the legal system. It can also take many different
forms. It might consist of a psychologist in court providing expert testimony concerning some
issue of relevance for a particular case. Alternatively, psychology in the law might consist of a
police officer using his or her knowledge of psychology in an investigation (ex. to extract
Psychology of the law
- Involves the use of psychology in the study of law itself and addresses questions such as, “what
role should the police play in domestic disputes?” It is often not considered a core topic in
forensic psychology. The challenge is that to address these sorts of questions, a set of skills from
multiple disciplines (criminology, sociology, law) is often important and sometimes crucial.
The history of forensic psychology th
- Relatively short history, dating back to the late 19 century and was typically not referred to as
Early Research: Eyewitness testimony and suggestibility
- In the 19 century, research in forensic psychology was taking place in North American and
Europe. Some of the first experiments were those of James McKeen Cattell (research in
intelligence testing) at Columbia University in NY. He was a previous student of Wilhelm Wundt,
who developed the first psychology lab in Leipzig, Germany, and was one of the major
powerhouses of psychology in North America. Cattell developed expertise in the study of human
cognitive processes in Leipzig and then conducted some of the first North American experiments
looking at the psychology of eyewitness testimony. He would ask people to recall things they
had witnessed in their everyday life and found that they were often inaccurate. Cattell =
psychology of eyewitness testimony
- Other psychologists began studying eyewitness testimony and suggestibility. The famous French
psychologist Alfred Binet conducted studies to show that testimony provided by children was
highly suggestible to suggestive questioning techniques. Binet demonstrated that asking
children to report everything they saw (free recall) resulted in the most accurate answers and
that highly misleading answers led to the least accurate answers.
- A German psychologist, William Stern, conducted studies examining the suggestibility of
witnesses after the Binet study. The “reality experiment” is now commonly used by eyewitness
researchers to study recall and recognition can be attributed to Stern. Like Binet, he found that
eyewitness testimony can often be incorrect and he was perhaps the first researcher to
demonstrate that a person’s level of emotional arousal can have an impact on the accuracy of
that person’s testimony.
Early Court Cases in Europe
- Psychologists in Europe were also appearing as expert witnesses in court. In 1896, Albert von
Schrenck-Notzing was probably the 1 expert witness to provide testimony in court on the effect
of pretrial publicity on memory. The case took place in Munich, Germany, and involved a series
of three sexual murders. Schrenck-Notzing testified that this extensive pretrial press coverage
could influence the testimony of witnesses by causing “retroactive memory falsification” –
where witnesses confuse actual memories of events with the events described by the media. He
supported this with lab research.
- Following this case, Julian Varendonck, a Belgian psychologist was called to be an expert witness
in 1911 for a case involving the murder of a young girl, Cecile. Varendonck concluded that many
children were easily led by suggestive questioning and that the court that the testimony
provided by the children in this case was likely inaccurate and, as a group, children are very
prone to suggestion.
Advocates of forensic psychology in North America - One of the most important landmarks was the publication in 1908 of Hugo Munsterberg’s On
the Witness Stand. Munsterberg was another student of Wundt and is considered to be the
father of forensic psych. He argued that psychology had much to offer to the legal system
including crime detection, false confessions, suggestibility, hypnotism, and crime prevention.
However, his ideas were presented in a way that led to heavy criticism from the legal profession.
- Munsterberg’s biggest critic was John Henry Wigmore, a law professor at Northwestern Uni in
Chicago (Treatise on Evidence). He put Munsterberg on “trial” and was found guilty of “claiming
more than he could offer”. He criticised him for the lack of relevant research publications to
back up his claims and lack of applied research in the field of forensic psych.
Forensic psychology in other areas of the criminal justice system
- Forensic psych gradually in North America gradually caught up with what was happening in
Europe. More research was being practically applied in a wide range of criminal justice settings.
Bartol and Bartol: forensic psychologists established the first clinic for juvenile delinquents in
1909, psychologists began usstg psychological testing for law enforcement selection purposes in
1917, and 1919 saw the 1 forensic assessment lab (pretrial assessments) set up in a US police
Biological, Sociological and Psychological Theories of Crime
- Sheldon’s constitutional theory (1949): crime is largely a product of an individual’s body build, or
somatotype, which is assumed to be linked to an individual’s temperament. Endomorphs
(obese) are jolly, ectomorphs (thin) are introverted, and mesomorphs (muscular) are bold.
Because of their aggressive nature, mesomorphs were more likely to become involved in crime
- Jacobs, Brunton, Melville, Brittan, and McClemont’s chromosomal theory (1965): chromosomal
irregularity is linked to criminal behaviour. A normal female has two X chromosomes and a
normal male has one X and one Y. It was discovered that there were men with two Y
chromosomes which was proposed to make them more masculine and aggressive. According to
Jacobs and her colleagues, this enhanced aggressiveness would result in an increased chance
these men would commit violent crimes
- Mark and Ervin’s dyscontrol theory (1970): lesions in the temporal lobe and limbic system result
in electrical disorganization within the brain which can lead to a dyscontrol syndrome.
Symptoms of this syndrome can include outbursts of sudden physical violence, impulsive sexual
behaviour and serious traffic violations
- Merton’s strain theory (1938): crime is largely a product of strain felt by certain individuals in
society (typically lower class) who have restricted access to legitimate means, such as education,
of achieving valued goals. While some individuals will be happy with the lesser goals, others will
turn to illegitimate means, such as crime, in an attempt to achieve the valued goals. - Sutherland’s differential association theory (1939): criminal behaviour is learned through social
interactions in which people are exposed to values that can be either favorable or unfavorable
to violations of the law. Sutherland maintained that people are likely to become involved in
criminal activity when they learn more values (attitudes) that are favorable to violations of the
law than values that are unfavorable to it.
- Becker’s labelling theory (1963): unlike most other theories of crime, he proposed that deviance
(antisocial behaviour) is not inherent to an act but a label attached to an act by society. A
“criminal” results primarily from a process of society labelling the individual as a criminal. This
process is thought to promote the deviant behaviour through a self-fulfilling prophecy defined
by Becker as a prediction, which is originally false but made true by the person’s actions.
- Bowlby’s theory of maternal deprivation (1944): early separation from one’s mother plays a role
in the development of antisocial behaviour. His theory is based on the study of juvenile
delinquents in which he found that a far greater number of delinquents experienced early
separation from their mothers compared to non-delinquent control group. This theory has been
criticised for his original control group to inadequate assessment procedures. However, negative
childhood experiences can indeed influence the development of antisocial behaviour.
- Eysenck’s biosocial theory of crime (1964): – 1 testable theory of criminal behaviour proposed
by a psychologist. He believed that some individuals (extraverts and neurotics) are born with
cortical and automatic nervous systems that influence their ability to learn from the
consequences of their behaviour, especially the negative consequences experienced in
childhood as part of the socialization and conscious-building process. Because of their poor
conditionability, it is assumed that individuals who exhibit high levels of E and N will have strong
- Gottfredson and Hirschi’s general theory of crime (1990): low self-control, internalized early in
life, in the presence of criminal opportunities explains an individual’s propensity to commit
Landmark court cases in the U.S.
- The first time expert testimony was used in the U.S. was in 1921 (State v. Driver). According to
Bartol and Bartol, the Driver case was only a partial victory. The court accepted expert evidence
from a psychologist in the area of juvenile delinquency – the court rejected the testimony.
- A more recent court case important to forensic psych history is the Brown v. Board of Education-
this case challenged the constitutionality of segregated public schools. On May 17, 1954, the
U.S. Supreme Court agreed against segregated schools. The famous footnote 11, work of
Kenneth Clark, an African-American psychologist at City College in NYC. This was the first time
that psychological research was cited in a U.S. Supreme Court decision and some have argued
that this validated psychology as a science.
- Court case of Jenkins v. United States- involved charges of breaking and entering, assault, and
intent to rape, with the defendant, Jenkins, pleasing not guilty by reason of insanity. Three clinical psychologists were presented, each supporting the insanity defense that the defendant
was suffering from schizophrenia. The judge told the jury to disregard the testimony and the
case was appealed. The issue in the case of Jenkins v. United States (1962) that is of most
interest to forensic psychologists is the admissibility of expert testimony from psychologists on
Signs of a Legitimate Field of Psychology
- Forensic psych is now a recognized and legitimate field of study within psychology. It is now
recognized as an establish discipline. There are a growing number of high-quality textbooks in
the area to teach students, particularly so in the U.S. There are now a large number of academic
journals dedicated to various aspects of the field, and more mainstream psychology journals are
beginning to publish research from the forensic domain at a regular rate. Third, a number of
professional associations have been developed to represent the interests of forensic
psychologists and to promote research and practice. The largest of these associations is the AP-
LS in which Canadian forensic psychologists have played a crucial role (Dr. James Ogloff). In
Canada, forensic psychologists can belong to the Criminal Justice Sections of the Canadian
Psychological Association (CPA). Lastly, new training opportunities in forensic psychology at the
undergraduate and graduate level are being established in North America and existing training is
- Dr. James Ogloff: University of Calgary- major in commerce transferred to psychology. Then
completed undergraduate research on eyewitness memory and hypnosis. Grad school in clinical
psych obtaining his M.A. at the University of Saskatchewan. He attended the Law/Psychology
program at the University of Nebraska at Lincoln which had the 1 program to offer a combined
law degree and Ph.D. in psychology. He completed his Juris Doctor in law and researched the
insanity defense due to interest spawned by John Hinckley Jr.’s attempted assassination of
President Ronald Regan. He began his academic career at Simon Fraser Uni and became the
University Endowed Professor of Law and Forensic Psychology. Currently he is the president-
elect of the Australian and New Zealand Association of Psychiatry, Psychology of Law and he is
the chair of the College of Forensic Psychologists in Australia.
Modern-day Debates: Psychological Experts in Court
- Topics that forensic psychologists testify about is very broad, including competency to stand
trial, custody issues, malingering and deception, the accuracy of eyewitness identification, the
effects of crime on victims and the assessment of dangerousness. It is important for them to
become more knowledgeable about the law and legal system, more aware of what the role of
an expert witness is, the various ways psychology and the law differ and the criteria that courts
consider when determining whether the psychological testimony should be admitted.
The Functions of the Expert Witness
- According to Ogloff and Cronshaw, an expert witness serves one of two functions: (1) to provide
the court with info that assists them in understanding a particular issue (2) provide the court with an opinion. These functions are what separate an expert witness (a witness who provides
the court with info/opinion that assists the court in understanding the issue of relevance to a
case) from other witnesses who appear in court (eyewitness etc.). Other witnesses can testify
only what they have directly observed (what they know to be fact) while expert witnesses can
provide their personal opinion and are allowed to draw inferences on their observations.
- These opinions and inferences must fall within the limits of expert witnesses’ areas of expertise
and the testimony must be deemed reliable and helpful to the court. They are supposed to be
educators to the judge and jury, not as an advocate for the defence or prosecution.
The Challenges of Providing Expert Testimony
- Expert testimony is effective but not simple. Manuals are used to help expert witnesses prepare
for court. Even judges can provide suggestions for forensic psychologists.
- According to Hess, psychology and law differ along at least 7 different dimensions: (1)
knowledge: knowledge in psychology is gained through cumulative research, in law, knowledge
comes from legal precedent, logical thinking and case law (2) methodology: methodological
approaches in psych are predominantly nomothetic (understand something by uncovering
broad patterns and general trends through use of controlled experiments and statistical
methods) while law is idiographic (understand something by examining details of individual
cases) this is why judges have difficulty seeing how psychologists can assist in court
proceedings (3) epistemology: psychologists assume it is possible to uncover hidden truths but
truth in law is defined subjectively (4) criteria: psychologists are cautious when attempting to
accept something as true while the law decides on what is true based on a single case and
criteria that are often more lenient (5) nature of law: the goal of psychology is to describe how
people behave and law is perspective, it tells people how they should behave (6) principles:
good psychologists consider alternative explanations for findings but good lawyers convince the
judge and jury that their explanation is the only correct explanation (7) latitude: the behaviour
of the psychologist when acting as an expert witness is severely limited by the court. The law
imposes fewer restrictions on the behaviour of lawyers.
- Little attempt has been made to understand these differences or their implications for forensic
Criteria for Accepting Expert Testimony
- Criteria for expert testimony have been in place since the early 20 century. Until recently,
admissibility of expert testimony in the U.S. was based on a decision handed down by the courts
in Frye v. United States (1923) – the court rejected the request to allow the polygraph expert to
present evidence on Frye’s behalf. The court indicated that, for novel scientific evidence to be
admissible in court, it must be established that the procedures used to arrive at the testimony is
generally accepted in the scientific community and in the particular field in which it belongs.
- This criterion is called the “general acceptance test – a standard for accepting expert testimony.
The major criticism centres on the vagueness of terms such as “general acceptance” and “the particular field” and whether trial judges are able to make appropriate determinations of what
these terms mean.
- The issue of vagueness was addressed in the U.S. Supreme Court decision handed down in
Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993), when more specific criteria were set. To
address the issue of “general acceptance”, the Supreme Court states that for scientific evidence
to be admitted into court it must (1) be provided by a qualified expert (2) be relevant and (3) be
reliable (scientifically valid). The U.S. Supreme Court laid out 4 specific criteria for accepting
expert testimony referred to as the Daubert criteria which suggests that: (1) the research has
been peer reviewed (2) the research is testable (falsifiable through experimentation) (3) the
research has a recognized rate of error (4) the research adheres to professional standards
- Kumho Tire Company v. Carmichael (1999), the U.S. Supreme Court rules that the Daubert
criteria apply to all expert testimony, not just scientific.
- the rules for admissibility in Canada were laid out in R. v. Mohan (1994) – established the
standard for admitting expert testimony in Canada. The standard is now referred to as the
Mohan criteria and includes: (1) the evidence must be relevant in that it makes a fact at issue in
the case more or less likely (2) the evidence must be necessary for assisting the trier of fact
(goes beyond the common understanding of the court) (3) evidence must not violate any rules
of exclusion (e.g. whether a witness is telling the truth) (4) the testimony must be provided by a
qualified expert, which is typically determined through training, experience and research
- the criteria are still highly subjective and rely on the discretion of the judge. Example of a
problem: R. v. McIntosh and McCarthy (1997)- judge decided that testimony related to the
accuracy of the eyewitness testimony was common knowledge and inadmissible – the judge was
most likely wrong in this case. Need for high-quality research in forensic psych as well as the
Judges currently use findings from psychological research to decide whether a witness on the stand is
lying or not. This is a good example of: psychology in law. Unit 2:
Chapter 11: Psychopaths
- Psychopaths have been called intraspecies predators. They seek vulnerable victims to use for
their own benefit. Lacking a conscious and feeling for others, they satisfy their own selfish needs
by preying on others. Psychopathy is a personality disorder defined by a collection of
interpersonal, affective, and behavioural characteristics, including manipulation, lack of
empathy, impulsivity, and antisocial behaviours. They are dominant, selfish, manipulative
individuals who feel no remorse or shame for behaviours that often has a negative impact on
- Murphy found that Inuit in Alaska use the term kulangeta to describe an individual who
“repeatedly lies and cheats and steals things and does not go hunting and, when the other men
are out of the village, takes sexual advantage of many women- someone who does not pay
attention to reprimands and who is always brought to elders for punishment”. They deal with
kulangeta by pushing them off the ice when no one is looking.
Assessment of Psychopathy
- Hervey Cleckley, a psychiatrist in Georgia, provided a definition for the psychopath in his book
The Mask of Sanity. He described 16 features, ranging from positive features, emotional-
interpersonal features, and behavioural problems. Currently, the most popular method of
assessing psychopathy in adults is the Hare Psychopathy Checklist-Revised (PCL-R) developed
by Robert Hare at the University of B.C. and strongly influenced by Cleckley.
- The PCL-R is a 20-item rating scale that uses a semi-structured interview and a review of file info
to assess interpersonal (e.g., manipulativeness), affective (e.g., lack of remorse), and behavioral
(e.g., impulsivity) features of psychopathy. Each item is scored on a 3-point scale: 2 indicates
that the item definitely applies to the individual; 1= to some extent; and 0= the symptom
definitely does not apply. The items are summed to = 0 to 40. They are subdivided into 3 groups:
a high PCL-R group (psychopaths)= 30 or greater; middle-scoring group (mixed group)= 20-30; a
low-scoring group (nonpsychopaths) = below 20.
- Factor analyses of the PCL-R indicated it consisted of 2 correlated factors – factor 1 reflects the
combination of interpersonal and affective traits and factor 2 is a combination of unstable and
socially deviant traits. Research has found that factor 1 is more strongly related to predatory
violence, emotional-processing deficits, and poor treatment response while factor 2 is strongly
related to reoffending, substance abuse, lack of education, and poor family background.
- Some researchers have argued for a three-factor model of psychopathy: (1) arrogant and
deceitful interpersonal style (2) deficient affective experience (3) impulsive and irresponsible
behaviour style. This splits factor 1 into two factors and removes some of the antisocial items
from factor 2. The most recent factor analysis of the PCL-R includes these three factors plus a 4 th
called antisocial that includes antisocial items.
- Another way of assessing psychopathic traits is via self-report questionnaires. Advantages: they
are able to measure those attitudes and emotions that are not easily observed by others (e.g., feelings of low self-esteem). They are easy to administer, quick to score and relatively
inexpensive. It is not necessary to worry about inter-rater reliability since only the individual is
completing the score. Also, some questionnaires include measures of response styles to detect
faking good or faking bad.
- Disadvantages of self-report: psychopaths often lie and some are known as “master
manipulators” and will say whatever will be in their best interests. They may not have sufficient
insight to accurately assess their traits. It will likely be difficult for them to report on specific
emotions if they have not experienced these emotions.
- Two of the most widely used self-report scales are the Psychopathic Personality Inventory-
Revised (PPI-R) and the Self-Report Psychopathy Scale (SRP). The PPI-R is a 154-item inventory
to measure psychopathic traits in offender and community samples. It has 8 content scales, 2
validity scales (check for carelessness and positive/negative response styles), and measures 2
factors (fearless dominance and self-centered impulsivity). The SRP is a 64-item self-report
measure to assess psychopathic traits in community samples. It consists of 4 factors: erratic
lifestyle, callous affect (e.g., “I am more tough-minded than other people), interpersonal
manipulation, and criminal tendencies.
- Canadian Researcher Profile: Dr. Robert Hare. One of the world’s leading authorities on
psychopathy. In the late 1970’s, he and his students and colleagues began developing what has
become the Hare Psychopathy Checklist-Revised (PCL-R) which is the leading instrument
worldwide for assessing psychopathy, both for scientific research and practical applications in
mental health and criminal justice. He is involved in a number of international research projects
in assessment and treatment issues, risk for recidivism and violence, and functional
neuroimaging. He has recently begun to study in the corporate world. He believes forensic
psychology researchers and clinicians should be familiar with important advances in
cognitive/affective neuroscience and their implications for forensic psychology.
- Subclinical Psychopaths: University Samples. Psychopathic traits are dimensional so people vary
on the number and severity of psychopathic features exhibited. Detecting Vulnerable Victims
(Wheeler, Book & Costello, 2009): university students were taped walking down a hallway and
classified as being vulnerable or not based on self-report victimization. Students with higher
SRP scores were more accurate at detecting victim vulnerability. Defrauding a Lottery (Paulhus,
Williams, & Nathanson, 2002): a student participates in a study and has a chance of winning
$100 and is asked to email the experimenter to let him know if they had previously been a
winner. Students scoring higher on the SRP were more likely to try and defraud the
experimenter and claim they were the “true” winner. Cheating on Exams (Nathanson, Paulhus,
& Williams, 2006): the experimenters wanted to determine which personality traits were
related to cheating. 4% of students were identified as cheating pairs, in which one student
copied the answers from an adjacent student. Psychopathic traits, as measured by the SRP (Self-
Report Psychopathy Scale), were the strongest predictors of cheating. Owning “Vicious” Dogs
(Ragatz, Fremouw, Thomas, & McCoy, 2009): owners of these 6 breeds were classified as
owning “vicious” dogs – Akita, Chow, Doberman, pit bull, Rottweiler, and wolf-mix. Students
classified as owning vicious dogs engaged in more criminal behaviours and scored higher on the
primary psychopathy scale (selfishness, carelessness and manipulation) of the Levenson Primary and Secondary Psychopathy Scale but were not more tolerant of animal abuse than other
Psychopathy and Antisocial Personality Disorder
- Antisocial personality disorder (APD) is a personality disorder in which there is evidence for
conduct disorder before age 15 and a chronic pattern of disregarding the rights of other since
age 15 – history of behaviour in which the rights of others are violated. After age 15, a person
with APD would need to display 3 or more of the following symptoms: repeatedly engaged in
criminal acts, deceitfulness, impulsivity, irritability, reckless behaviours, irresponsibility, lack of
- Additional confusion surrounds the diagnosis of APD and its relationship to both psychopathy
and sociopathy (a label used to describe a person whose psychopathic traits are assumed to be
due to environmental factors). These three are sometimes used interchangeably but are actually
related but distinct.
- The term sociopath was coined in 1930 by Partridge to describe those people who had problems
with or refused to adapt to society. Lykken proposed that sociopaths manifest similar traits as
psychopaths but develop these traits as a result of poor parenting and other environmental
factors, whereas psychopaths are genetically predisposed to a temperamental that makes them
difficult to socialize. The term sociopath is rarely used in empirical literature and no assessment
instruments have been developed for it.
- APD places more emphasis on antisocial behaviours than does the PCL-R. The prevalence of APD
is very high in prisons with up to 80% of adult offenders being diagnosed with this disorder.
Using a cut-off of 30 on the PCL-R, 10-25% of adult offenders can be classified as psychopaths.
An asymmetrical relation exists between the two disorders: nearly all psychopathic offenders
meet diagnostic criteria for APD, but most offenders diagnosed with APD are not psychopaths.
APD symptoms are most strongly related to the behaviour features of psychopathy and not to
the interpersonal or affective features.
Forensic use of Psychopathy
- Zinger and Forth reviewed cases in which an expert testified about psychopathy, sociopathy, or
APD, whereas in more recent studies by DeMatteo and Edens, and Walsh and Walsh only cases
in which the PCL-R was used by the expert were included. The majority of the testimony
regarded psychopathy being associated with an increased severity of disposition.
- In Canada, psychopathy and associated constructs were used in making sentencing decisions: to
support a case’s transfer from youth to adult court, to contribute to dangerous offender
hearings, to help to determine parole eligibility, and to assess mental state at time of offence
hearings. In the U.S., the PCL-R was also used in sexual violent predator evaluations and death-
penalty sentencing and in civil cases for child custody decisions a diagnosis of psychopathy,
sociopathy, and APD is an aggravating factor for the death penalty and considered to be
associated with a higher risk of violent recidivism and lack of treatment responsivity in
dangerous offenders. In regards to the insanity defense, a diagnosis of psychopathy does fulfill the disease of the mind requirement but it has never fulfilled the second requirement of not
appreciating the nature or quality of the act or knowing that it is wrong.
Psychopathy and Violence
- Characteristics of psychopathy are compatible with a criminal lifestyle (violence in particular)
and a lack of concern for societal norms. Psychopaths make up a relatively small proportion of
the population but their involvement in serious repetitive crime and violence is out of
proportion to their numbers. Hart – “the two are so intimately connected that a full
understanding of violence is impossible without consideration of the role played by
- Psychopaths are high-density (prolific), versatile offenders (from minor theft and fraud to
murder). They start their criminal career at a younger age and persist longer, engage in more
violent offences, and commit a greater variety of violent offences, engage in more violence
within institutions and are more likely to be violent after release.
- The nature of their violence differs from other types: “psychopathic violence is more likely to be
predatory in nature, motivated by readily identifiable goals, and carried out in a callous,
calculated manner without the emotional context that usually characterizes the violence of
other offenders”. Offenders that engage in instrumental violence (premeditated violence to
obtain some goal) score significantly higher on measures of psychopathy than do offenders
engaging in reactive violence (impulsive, unplanned that occurs in response to provocation).
- One study by Williamson, Hare, and Wong (1987) found that when nonpsychopaths commit
violence, they are likely to target people they know and their violent behaviour is likely to occur
in the context of strong emotional arousal. Psychopaths are more likely to target strangers and
be motivated by revenge and material gain. Studies on adolescent offenders found that youth
who engaged in instrumental violence were more psychopathic than other youth.
- Psychopaths’ use instrumental violence extend to homicide. Woodworth and Porter used a PCL-
R scores to divide 135 Canadian offenders into the 3 groups: nonpsychopaths, medium scorers,
and psychopaths (scores of 30 or greater)- the percentage of homicides that were primarily
instrumental were 28%, 67% and 93% respectively. The researchers concluded that psychopaths
engage in “cold-blooded” homicides much more often than nonpsychopaths.
- In a study of post-homicide behaviours, Hakkanen-Nyholm measured psychopathic traits in 546
Finnish homicide offenders. Higher PCL-R scores were found for cases with multiple offenders,
stranger victims, and male victims; for offenders who left the scene of the murder; and for
offenders who denied responsibility. Rather than experiencing remorse , psychopathic offenders
shifted the blame and focused on “saving their own skin”.
- Porter, ten Brinke, and Wilson found evidence for psychopaths’ ability to manipulate the
criminal justice system. They were released from prison more often than nonpsychopathic
offenders. However, when followed-up on, the psychopathic offenders were less successful than
nonpsychopathic offenders ability to engage in impression management (telling people what
they want to hear). - Clifford Olsen: A Predatory Psychopath. 1997, a jury in Surrey, B.C. took 15 min. to reject Clifford
Olson’s bid for early parole. He is serving a life sentence for murdering 11 children in 1980-1981.
He made a deal with the police called “cash for corpses” deal. He negotiated a payment of $10
000 for each body he uncovered for the RCMP, the money would go to his wife. $100 000 was
paid to this trust fund. Faint hope clause introduced in 1976 to the section 745 of the Criminal
Code that after 15 years in prison, murders can apply for a judicial hearing to request early
parole (was replaced by mandatory life sentences for 1 and 2 degree murder). Dr. Stanley
Semrau, a forensic psychiatrist was hired to evaluate Olson and assessed him with the Hare
Psychopathy Checklist-Revised and gave him a score of 38 out of 40. Multiple murderers are
now ineligible for a section 745 review which started in 1997. He is currently in the maximum-
security prison in Quebec.
- Psychopathy in Animals? Soloman compared dog breeds on being able to resist a tempting treat
that was associated with punishment. Certain dogs quickly learned to resist temptation
(Shetland sheepdogs) whereas “Basenjis seem to be constitutional psychopaths and it is very
difficult to maintain taboos in such dogs”. Lykken describes the bull terrier as sharing similar
features to human psychopaths such as being fearless and immune to punishment. Lilienfeld
and colleagues conducted the most detailed investigation and measured psychopathic traits in
chimps. The Chimpanzee Psychopathy Measure (CPM) consists of 23 items rated on a 5-point
scale, including items such as deceptive, greedy, aggressive, confident, boredom prone and
dominant. 34 chimps were housed at the Yerkes Regional Primate Research Center in Georgia.
Male chimps scored higher on the CPM and the CPM was positively related to observer ratings
of sexual activity, daring behaviours, teasing bluff displays, and temper tantrums, and was
negatively related to generosity.
Psychopaths in the Community
- Much of the research in community samples has used the Hare Psychopathy Checklist:
Screening Version. This 12-item takes less time to administer and places less emphasis on
criminal behaviour for scoring than the PCL-R. Coid et al. found that only 0.6% of the sample had
scores of 13 or greater on the PCL:SV (only one person scored above the cut-off score of 18),
with 71% having no psychopathic traits (scoring 0). Another community sample in the U.S. found
75% of the sample had scores of 2 or less and only 1.2% had scores in the “potential
psychopathic” range (scores of 13 or greater). Regardless of the sample, females consistently
score lower than males on the PCL:SV and other measures.
- Babiak found employees with many psychopathic features to be the root of some of the
company problems. These employees were skilled at getting info on other employees, spreading
unwarranted vicious rumours about others and causing dissention among employees. They
were good at manipulating and blaming others for their failures.
- More recently, Babiak, Neumann and Hare assessed psychopathic traits in 203 corporate
professional. The average PCL-R score was 3.6 and 8 professionals scored above 30 for a
diagnosis of psychopathy. The more psychopathic professionals were more creative engaged in
more strategic thinking and had stronger communication skills. - Only one study exploring the experiences of victims of psychopaths. Kirkman aimed to identify
the behavioural and personality characteristics of nonincarcerated psychopathic males who may
or may not have abused their partners. 8 characteristics of male psychopaths in heterosexual
relationships were extracted from interviews: (1) talking victims into victimization (2) lying (3)
economic abuse (4) emotional abuse/psychological torture (5) multiple infidelities (6) isolation
and coercion (7) assault (8) mistreatment of children
Trauma is not a necessary precursor for psychopathy.
Psychopathy and Sexual Violence
- Psychopathy is only weakly associated with sexual offences. Brown and Forth reported that in a
sample of 60 rapists, their PCL-R score was associated with their number of prior offences but
not the number of prior sexual offences. Porter, Fairweather, et al. fund that psychopaths
engaged in significantly more violent offences but engaged in fewer sexual offences than
nonpsychopaths potential explanation is the high rate of sexual offending found in child
molesters, who tend not to be psychopaths.
- Offenders who commit sexual homicides (homicides that have a sexual component or in which
sexual arousal occurs) are the most psychopathic, followed by mild sexual offenders (sexually
assault both children and adults), followed by rapists, with the lowest psychopathy scores found
among child molesters.
- Brown and Forth examined motivations for psychopathic and nonpsychopathic rapists. The
Massachusetts Treatment Center Rapist Typology (MTC:R3) identifies different types of rapists
based on motivation and level of social competence. They reported that 81% of psychopathic
rapists were opportunistic or vindictive, as compared to 56% of nonpsychopathic rapists who
were more likely to report feelings of anxiety or alienation leading up to the rape, whereas
psychopaths reported positive emotions. Porter, Woodworth, Earle, Drugge, and Boer
investigated the relation between psychopathy and severity of violence in sexual offenders.
Level of sadistic violence (evidence for overkill and enjoyment) was related to the PCL-R total
scores and with the interpersonal and affective features of psychopathy.
- Study of 100 male German forensic patients (all sexual offenders), Mokros et al. studies the
association between psychopathy and sexual sadism (people sexually aroused by fantasies,
urges, or acts of inflicting pain, suffering or humiliation on another human). PCL-R total scores,
affective deficits facet, and antisocial facets were all related to sexual sadism.
Psychopathy and Treatment
- Hare: “unlike most other offenders, they suffer little personal distress, see little wrong with their
attitudes and behaviour, and seek treatment only when it is their best interests to do so”.
- Best known retrospective study on treatment by Rice, Harris, and Cormier – investigated effects
of intensive therapeutic treatment program on violent psychopathic and nonpsychopathic
forensic psychiatric patients. Using a matched group design and file information, all patients
were scored on the PCL-R and were divided into psychopaths (scores of 25 or greater) and nonpsychopaths (scores of less than 25). Patients were followed for ten years after their release.
The violent recidivism rate was 39% for untreated nonpsychopaths, 22% for treated
nonpsychopaths, 55% for untreated psychopaths, and 77% for treated psychopaths. Treatment
was associated with a reduction in violent recidivism among nonpsychopaths but an increase
- Reasons why a treatment may not work include use of an inappropriate treatment and
problems in implementing the treatment such as inadequate training of those administering it
or lack of support from management. A more promising outcome study was reported by Oliver
and Wong- found that although psychopathic sex offenders who dropped out of treatment were
more likely to violently reoffend, those psychopathic sex offenders who stayed in treatment
showed positive treatment gains and were less likely to violently reoffend.
Psychopathy in Youth
- The assumption is that psychopathy gradually develops from various environmental and
biological antecedents. Two assessment instruments have been adapted from the PCL-R: one for
use with children and the other for adolescents. The Antisocial Process Screening Device (APSD)
is designed for assessing the precursors of psychopathic traits in children. The child is assigned a
rating on various questions by parents or teachers. A self-report version of this scale has also
been developed for use with adolescents.
- Frick, Bodin, and Barry found that the APSD had a three-dimensional structure consisting of a
callous-unemotional factor, an impulsivity factor, and a narcissism factor. The Hare Psychopathy
Checklist: Youth Version (PCL:YV) is a rating scale for measuring psychopathic traits and
behaviours in adolescents between 12-18.
- One concern has been the use of a label psychopath, a label that has many negative
connotations. Murrie, Cornell, Kaplan, et al.: “the use of the label psychopath has ominous
connotations that may adversely influence treatment decisions, social service plans, and juvenile
- Psychopathy in adults is associated with violence, assumed to be a stable trait, and is resistant
to intervention attempts. A study using the APSD has indicated a fairly high stability across a 4
year period. The only longitudinal study to assess psychopathic traits in youth and reassess for
psychopathy in adulthood was recently completed by Lynam et al. The results indicated that
there was a moderate degree of stability in psychopathic traits from age 13-24. A concern is
whether scores on measures of psychopathy arguable may be inflated by general characteristics
of adolescence – studies have found the scores on psychopathy measures of community youth
to be very low.
- Research using PCL:YV has found that adolescents with many psychopathic traits become
involved in criminal behaviours at an earlier age, engage in more violence in institutions and in
the community, and are at a higher risk of reoffending once released. In contrast however,
research has questioned the utility of the PCL:YV to predict violence in adolescent female
offenders. - Campbell, Porter, and Santor found that psychopathic traits were related to delinquency and
aggression but not to anxiety or depression symptoms in a sample of adolescents.
- Youth with psychopathic traits may be more responsive to interventions. In contrast, O’Neill,
Lidz and Heilbrun examined treatment outcome in a sample of 64 adolescent substance abusers
and found that youth scoring high on the PCL:YV showed poor program attendance, poor quality
of participation and less clinical improvement and were more likely to reoffend after completing
the program. Caldwell et al. compared the treatment outcome of two groups of incarcerated
youth, both with very high PCL:YV scores. Youth who were released from the correctional centre
violently reoffended at twice the rate in a 2 year follow-up compared with the youth receiving
the intensive treatment at the treatment centre.
- concerns (1) the issue of labelling a youth as a psychopath (2) the stability of psychopathic traits
from late childhood to early adulthood (3) the possibility that characteristics of psychopathy are
common features of normally developing youth
Psychopathy Label: The Potential for Stigma. In the Edens et al. study, the defendant was described as a
psychopath, psychotic, or having no mental disorder. Mock jurors were more likely to support the death
penalty for the psychopathic defendant than for the psychotic or nondisordered defendant. In another
Edens study, the mock jurors presented with the psychopathic traits version were more likely to support
the death penalty and to be less supportive of the defendant receiving intervention in prison. They are
also less likely to support the death penalty for juveniles than for adults. Murrie et al. found that in
contrast to the above studies, the diagnostic label was not strongly related to probation officers’
recommendations of type of sanction, risk level, or treatment amenability.
Psychopathy: Nature versus Nurture
- Person’s innate characteristics (nature) as compared with their personal experiences (nurture).
Growing evidence suggests a strong genetic contribution to psychopathy. Investigators try to
hold constant the effect of either genes or environment. This typically involves comparing
individuals who have similar genes raised in different environments. Identical twins (share all
their genes) can be compared when raised apart. This holds genetic influences constant while
allowing the environment to vary. Also, fraternal twins (share half their genes) raised together
can be compared with identical twins raised together. Biological siblings (share half their genes)
raised together can be compared with adoptive siblings (share no genes but are raised in same
- Only studies done to compare heritability of psychopathic traits are studies comparing identical
and fraternal twins. In a study of adult male twins, Blonigen et al. had each pair of identical and
fraternal twins complete the Psychopathic Personality Inventory (PPI). Identical twins were
much more similar in their scores. Genetic influences accounted for between 29 – 59% of the
variance for each of the different PPI subscales. In a twin study in Sweden, Larsson et al. found a
strong genetic influence as well using the Youth Psychopathic Inventory. In a sample of 7 year
old twin pairs in the U.K., Viding et al. found that callous-unemotional traits were moderately to
highly heritable. Environmental factors may influence how these innate traits are expressed. Does Family Matter?
- The best method to determine whether family experiences are related to the development of
psychopathy is to do a prospective longitudinal study – study a group of children and follow
them through childhood, adolescence, and into adulthood, measuring family background
variables and psychopathic traits. This allows researcher to avoid retrospective bias (reconstruct
past events so that they are consistent with current beleifs) and to establish causal order.
- The Cambridge Study in Delinquent Development is a 40-year prospective study of antisocial
behaviour of 411 London boys who have been followed up from age 8-48 and assessed using the
PCL:SV. Farrington reported that of those men scoring 10 or more, 97% had been convicted of
an offence and 48.5% of these men were chronic offenders (more than 10 times). Measuring
family background variables between ages 8-10, the best predictors of adult psychopathy were
having criminal father or mothers, being a son whose father was uninvolved, having a low family
income, coming from a disrupted family, and experiencing physical neglect.
- In another longitudinal study by Weiler and Widom, they used court records to identify over 900
children who had been abused or neglected prior to age 11 and compared them with a control
group matched on age, race, gender, elementary school class, and place of residence. Children
were followed up after 20 years and assessed on a modified PCL-R. Children who had been
abused had slightly higher PCL-R scores.
- There are multiple developmental pathways to the development of psychopathy.
Psychopathy and Law Enforcement
- O’Toole: “psychopathy can be described as one of law enforcement’s greatest challenges”.
Pinizzotto and Davis conducted a study of the characteristics of killers of police officers. Almost
half of these killers had personality and behaviour features consistent with psychopathy.
O’Toole described the potential crime scene characteristics manifested by a psychopathic
violent offender. For example, impulsivity (feature of psychopathy) can be manifested at a crime
scene by injury pattern of the victim, choice of weapon, and time and location of the crime.
However, some are charming and manipulative.
- Another challenge for law enforcement personnel is to develop effective methods for
interrogating psychopathic suspect. Appealing to the psychopath’s sense of grandiosity and
need for status might be more productive. Quayle, a police officer in the U.K. suggests that
psychopathic suspects are likely to engage in the following types of behaviours during
interrogation: try to outwit the interrogator, enjoy being the focus of attention, attempt to
control the interrogation, will not be fooled by bluffs, attempt to shock.
- Quayle has offered suggestions for interviewing: case familiarity (be familiar with the evidence
to counteract the psychopath’s evasiveness and deceitfulness), convey experience and
confidence, show liking or admiration, avoid criticism, avoid conveying emotions
What Makes Them Tick? Cognitive and Affective Models of Psychopathy - Newman et al. have proposed that psychopaths have a response modulation deficit. According
to the theory, psychopaths fail to use contextual cues that are peripheral to a dominant
response set to modulate their behaviours. if they are engaging in specific rewarded behaviour,
they will not pay attention to other information that might inhibit their behaviour – why they
fail to learn to avoid punishment (poor passive avoidance)
- The other theory proposes that psychopaths have a deficit in the experience of certain critical
emotions that guide prosocial behaviour and inhibit deviance. Hervey Cleckley was the first
person to theorize that psychopaths have a deep-rooted emotional deficit that involved the
disconnection between cognitive-linguistic processing and emotional experience. Williamson,
Harpur, and Hare administered a lexical-decision task to psychopathic and nonpsychopathic
offenders. Emotional and neutral words and nonwords were presented and participants
indicated whether what was on the screen was a word. When the word was emotional,
nonpsychopaths were able to do this faster than if the word was neutral. Psychopaths fail to
show the normal, faster reaction time to emotional words. They also found that psychopaths’
brain-wave activity does not differentiate between emotional and neutral words.
- Blair et al. asked children to identify emotions in neutral words spoken with intonations
conveying happiness, disgust, anger, sadness and fear. Boys with many psychopathic traits were
impaired at recognizing fearful vocal affect. In adults, Patrick et al. compared startle reflexes of
psychopathic and nonpsychopathic sexual offenders to slides of positive, neutral, and negative
stimuli. The startle-elicited blinks of nonpsychopathic offenders were smaller when watching
positive slides, moderate when watching neutral slides and enhanced when watching negative
slides. In contrast, psychopathic offenders’ startle-elicited blink did not differ in magnitude
across the different types of slides.
- Amygdala dysfunction theory: the amygdala is a small almond-shaped structure in the medial
temporal lobes. It is part of the limbic centre, which regulates the expression of emotion and
emotional memory. It is linked to other brain regions responsible for memory, control of
autonomic nervous system, aggression, decision making, approach and avoidance behaviour,
and defense reactions. Other researchers have proposed a paralimbic model to explain the
emotional deficits seen in psychopaths. Newman et al. have argued that the emotional deficits
seen in psychopaths can be explained by an attention deficit and are not due to an amygdala-
Chapter 1: Pg. 13
Biological, Sociological and Psychological Theories of Crime
- Sheldon’s constitutional theory (1949): crime is largely a product of an individual’s body build, or
somatotype, which is assumed to be linked to an individual’s temperament. Endomorphs
(obese) are jolly, ectomorphs (thin) are introverted, and mesomorphs (muscular) are bold.
Because of their aggressive nature, mesomorphs were more likely to become involved in crime - Jacobs, Brunton, Melville, Brittan, and McClemont’s chromosomal theory (1965): chromosomal
irregularity is linked to criminal behaviour. A normal female has two X chromosomes and a
normal male has one X and one Y. It was discovered that there were men with two Y
chromosomes which was proposed to make them more masculine a