Psychology is concerned with the understanding, explanation, and control
of the causes of human behaviour and experience.
Law is the sum of all rules governing behaviour that is enforceable in courts.
Reflects values of what behaviour is acceptable and what is not
What do you want to get out of this course?
What I hope to get out of this course is a deeper understanding of
the area of forensic psychology and explore the various topics that
exist within this area. I am interested to learn about the different
areas of forensic psychology and hope to find one domain that may
lead to a possible career path for myself.
In what ways do you think the study of human behaviour can have
practical applications to the law?
Studying human behaviour can have practical applications to the
law when policies are put in place by the government. Since laws
are created to control behaviour, there should be some examination
of behaviour so the policies put in place can be effective. Studying
human behaviour can also be applied to the law in how those who
break the law should be treated. By studying criminals and what
leads them to breaking the law, it could lead to prevention
programs or interventions to help reduce crime.
What are your initial „biases‟ or attitudes regarding “Psychology and
My attitudes towards psychology and the law are that there is a
great deal of misrepresentation by the media of what those who
study in this field do. In popular televisions shows like Criminal
Minds, the investigations are quite fast-paced and intricate. I feel
like what is represented by these shows is not entirely accurate,
and I want to know what is actually studied regarding psychology
and the law.
Common “understandings” of the criminal justice system:
There are many different levels of the system that deal with
different issues (government, police, courts…). Can be like machines that are connected to each other.
Information is fed from one machine to the next through files and
Justice is a human product and the CJS does not actually run as
smoothly as a machine.
o Those who make the laws are the ones running the process,
and forensic psychology analyses their decisions and motives
in their choices. Chapter 1: An Introduction to Forensic Psychology
Forensic psychology is a field of psychology that deals with all aspects of
human behaviour as it relates to the law or legal system.
Narrow definitions would exclude those who conduct forensic-
Focus should be on the application and research to inform applied
practice in the field of forensic psychology.
TV and its Influence:
Is this influence problematic?
o Accuracy in portrayals: they may not be showing all of the
facts, they may just be showing you a selective story through
Roles of a Forensic Psychologist:
All are interested in issues that arise at the intersection between
psychology and the law.
What differs is the focus that the psychologist takes.
Clinical forensic psychologists are psychologists who are broadly
concerned with the assessment of mental health issues as they
pertain to the law or legal system.
o This can include research and practice in a variety of settings.
o They have to be licensed to practice in Canada, and specialize
in the forensic area.
o They view mental illness as a product of an individual‟s
physiology, personality, and environment.
Forensic psychiatry is a field of medicine that deals with all
aspects of human behaviour as it relates to the law or legal system.
o They are medical doctors that can prescribe medication. They
rely on the medical model of mental illness.
Experimental forensic psychologists are broadly concerned with
the study of human behaviour as it relates to the law or legal
o They can be found in a variety of criminal justice settings.
o Their focus is not just on mental health issues. Their
research can be on any issue that relates to the law or legal
system. o This area is more varied in training since there are different
areas of expertise.
Some may be more of a legal scholar. These scholars may have
their Ph.D. in psychology and their L.L.B. in law.
o They are more informed about the legal process and the legal
o Focus would be on policy analysis and legislative consultation.
Relationship Between Psychology and Law:
This area of study can be approached from many different angles.
Psychology and the law uses psychology to examine the
operation of the legal system.
o Examining or analyzing components of the law from a
psychological perspective. They are seen as separate
o Answering questions that are communicated to the legal
Psychology in the law uses psychology in the legal system as the
o Using what is known from psychology in the legal system
Psychology of the law uses psychology to examine the law itself.
o The domain of the legal scholar.
o Answering the questions that may be posed requires skills
from other disciplines (criminology, sociology, law).
History of Forensic Psychology:
Has a relatively short history that dates back to the 19 century. It
may not have been seen as forensic psychology back then.
Eyewitness Testimony and Suggestibility:
James McKeen Cattell had done some experiments in eyewitness
testimony (late 19 century). He asked people to recall things they
had witnessed in their everyday lives and found that their answers
were often inaccurate.
Other psychologists began to study eyewitness testimony and
suggestibility around the same time. o Alfred Binet showed that children are highly susceptible to
suggestive questioning techniques.
Free recall results in the most accurate answers and
highly misleading questions result in the least accurate
o William Stern conducted the “reality experiment” that
demonstrated 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 were starting to appear as expert witnesses in court.
o They were used mostly to deal with issues surrounding the
accuracy of eyewitness testimony.
Ex. Schrenck-Notzing and retroactive memory
falsification. He talked about how the press coverage
could influence the testimony of a witness.
Advocates of Forensic Psychology in North America:
Hugo Munsterburg‟s On the Witness Stand (1908) showed that
psychology could provide much to the legal system. He felt that
issues that have been studied could be applied in the legal field.
o This has pushed more psychologists into the legal arena.
Forensic Psychology in Other Areas of the Criminal Justice System:
Theories were being proposed at a rapid rate after Munsterburg‟s
book was released.
Research was being applied in a wide range of criminal justice
o Clinics were created for juvenile delinquents, psychological
tests were needed for police officers, forensic laboratories.
Landmark Court Cases in the United States:
The first time expert testimony was used in the US was in 1921 for
the State v. Driver case.
o There was the rape of a girl and the psychologist had claimed
that the girl was a moron and could not be believed. The
court rejected the psychologist‟s testimony.
Brown v. Board of Education (1954) challenged the
constitutionality of segregated schools. o It was seen to create a sense of inferiority that has an effect
o Psychological research was used to show how discrimination
and segregation can have effects on people‟s personality. It
was the first time that psychology was validated as a science
and cited by the Supreme Court.
Jenkins v. United States (1962) dealt with the use of
psychologists used to support insanity defences. Three clinical
psychologists had claimed the defendant had schizophrenia, but the
judge told the jury to dismiss their testimony because they were
not qualified to provide expert testimony.
o The case was appealed and the APA gave a report saying that
they were qualified to provide opinions on mental illnesses.
o The psychologist has to be competent to give expert opinions,
it depends on their knowledge and not just that they have the
title of „psychologist‟.
o This helped to increase the extent to which psychologists
could contribute directly to the legal system as expert
Signs of a Legitimate Field of Psychology:
It is a recognized and legitimate field within psychology.
There are many textbooks available for students to use to study the
There are plenty of academic journals dedicated to aspect of the
Professional associations have been developed to represent the
interests of forensic psychologists.
o American Psychology-Law Society (AP-LS).
Training opportunities are established at the undergraduate and
The APA has formally recognized forensic psychology as a specialty
Modern-Day Debates: Psychological Experts in Court: Those who testify in court may do so for various topics that range
from competency to stand trial, deception, eyewitness
identification, the effects of crime on victims…
They have to become more knowledgeable on law and the legal
system to contribute to the judicial system in the ways they want
The Functions of the Expert Witness:
Expert witness is a witness who provides the court with
information (often an opinion on a particular matter) that assists
the court in understanding an issue of relevance to a case.
They help the court understand a particular issue and give an
opinion regarding the issue.
It is important to understand their function to know what makes
them different from other witnesses that appear in court.
o Other witnesses can only discuss what they have directly
observed. Experts can provide their opinions and draw
inferences from their observations.
Their opinions have to fall within their area of expertise that they
gained through training and experience.
Are more of an educator to the judge and jury than an advocate for
The Challenges of Providing Expert Testimony:
There have been several manuals published to assist expert
witnesses with the task of preparing for court.
The differences between psychology and law has made it difficult
for forensic psychologists to be effective in court.
o Knowledge: psychology takes more of a cumulative approach
where law deals with precedence.
o Methodology: they take a nomothetic (looking at patterns and
trends through experiments and statistics) where law is
idiographic (case-by-case basis).
o Epistemology: assume that the truth can be uncovered if the
appropriate experiments are conducted and the truth in law is
defined subjectively and based on who can provide the most
convincing story of what happened. o Criteria: they are cautious to accept something as true where
it has to be replicated and law decides what is true based on
a single case and lenient criteria.
o Nature of law: describes how people behave where law tells
how people should behave (prescriptive).
o Principles: always consider alternative explanations for their
findings where lawyers try to convince a jury that their
findings is the only correct explanation.
o Latitude: their behaviour when acting as a witness is limited
where lawyers have less restrictions placed on their
Understanding the differences helps us appreciate why courts are
sometimes reluctant to admit testimony provided by psychological
Criteria for Accepting Expert Testimony:
The admissibility of expert testimony in the US was based on a
decision handed down by the courts in Frye v. United States
o He was tried for murder and the court rejected his request to
admit the results from a polygraph exam that he passed.
o The appeal allowed for a polygraph expert to present
evidence on Frye‟s behalf.
o It must be established that the procedure used to arrive at
the testimony us generally accepted in the scientific
o General acceptance test is a standard for accepting expert
testimony, which states that expert testimony will be
admissible in court if the basis of the testimony is accepted
within the relevant scientific community.
The test is quite vague in what they mean when they
say general acceptance. How could the judge know if
their views are accepted by their community?
This issue was addressed by the Duabert v.
Merrell Dow Pharmaceuticals, Inc. (1993). It
set more specific criteria for admissibility in court.
He sued the company because he thought that the drugs his mother took from the company had
led to his birth defects. The evidence that his
experts was rejected since it was not widely
accepted the methods used to arrive at their
results. His lawyer appealed based on the state‟s
interpretation on “general acceptance”.
For scientific evidence to be admitted into court, it must:
o Be provided by a qualified expert.
o Be relevant.
o Be reliable (scientifically valid).
Daubert criteria is a standard for accepting expert testimony,
which states that scientific evidence is valid if the research on which
it is based has been peer reviewed, is testable, has a recognized
rate or error, and adheres to professional standards.
R. v. Mohan (1994) set out rules of admissibility in Canada.
o Mohan was a pediatrician that was charged with sexually
assaulting his female patients. He had expert testimony
testify that the typical offender would be a pedophile, and he
was not a pedophile. The judge ruled that the testimony was
inadmissible and the Supreme Court agreed.
o Mohan Criteria is a standard for accepting expert testimony,
which states that expert testimony will be admissible in court
if the testimony is relevant, is necessary for assisting the trier
of fact, does not violate any exclusionary rules, and is
provided by a qualified expert.
It has to make a fact at issue in the case more or less
The testimony has to be something that goes beyond
the common understanding of the court. They should
not be presenting common sense things.
If the testimony has a potential prejudicial effect
outweighs the probative value, the testimony is
Expertise is usually determined by considering the type
and amount of training and experience a witness
possesses. Exercise 1.2
Henke 1838 wrote:
o When a person presents themselves as an expert, there
should be people there in similar positions to identify them as
o They should be able to name reasons why they were chosen
from the other people who could have been a witness.
o The investigator has to try to remove any changes that may
have occurred that can impair recognition (prison clothes,
o The investigator must beware not to draw the witness‟
attention to the person through facial expressions... that
make the person different from others.
o If identification is to be carried out as a confrontation, it has
to be carried out in such a way that the person identified is
unaware of it and cannot see the witness.
they should be placed in separate rooms that are
connected by a communication door which has an
opening large enough for observation.
The beginnings of scientific psychology can be traced to Wilhelm
Wundt of Germany in 1879.
There is no one person who found the forensic psychology
movement, but many helped contribute.
o Freud thought the psychology could help the legal system by
offering its methods and understandings to the testing of the
truthfulness of reported events.
o Muensterberg argued that insights from experimental
research on the psychology of perception and memory could
address the accuracy and credibility of eyewitness testimony.
He did not appreciate that the court was more
concerned with the validity and reliability of verdicts
than the reliability of witnesses.
o Binet demonstrated the power of suggestibility on children‟s
memory. o Stern provided evidence on the psychology of verbal reports
as it occurs in the law. Error-free recollection is the exception
not the rule.
o Memory recall has been shown to decline over time, and
witnesses are inferior in interrogatory recall compared to free
o There was interest in the 1930s, 1960s. new interest was
shown in the 1970s. it has continued to grow and expand
Since psychology and the law have had interaction tracing back to
the 19 th and 20 th centuries why were these early psychology
contributions (by Freud, Muensterberg, Binet, Strern & von Listz)
either ignored or resisted by the legal community?
The contributions of early psychologists may have been ignored or
resisted by the legal community due to the differences that exist
between the psychology and the law. Within Muensterberg‟s book
On the Witness Stand, he pushed to have more psychologists within
the legal field to share their findings on the accuracy and credibility
of eyewitness testimony. As the course manual discusses, the legal
community was not interested in concerned with the reliability of
the witnesses but rather whether the verdict was valid. As the
scientific community began to support the methods of
psychologists, there was more interest from the legal community in
accepting psychological contributions.
Science and Methodology:
Philosophy of Science
Charles Pierce offered 4 general principles about how people
develop knowledge about the world.
o Method of tenacity: people hold beliefs about others and how
the world works because they know its true based on their
experience. They will keep believing them even if faced with
contradictory evidence because they have always known
them to be true. o Method of authority: people will believe things because a
person of authority declares it to be so.
o A priori method: an idea is believed to be right because it can
be logically deduced as the way to knowledge. These are
considered universal truths. It is based on positive law (the
law on the books). This is the dominant approach in the legal
o Method of science: test statements through observations and
systematic research. It helps us to recognize the probabilities
of events and base decisions on the best of our knowledge. It
is the dominant approach in psychology.
Psychology systematically studies behaviour whether it is
observable or internal.
Legal psychology draws theoretical base from several fields of
research (developmental, abnormal, clinical, social…)
o Based on empirical studies of behaviour.
o Their methods are testable, logically consistent, precise,
comprehensive, and parsimonious (simple).
Researchers tend to select problems for their study that
are consistent with their own values.
Value judgments affect the design of research projects
and the interpretations of their results.
Science is a quest for theoretical knowledge lit by seeking general
explanatory principles what accounts for the indeterminate range of
the phenomena and that their theory is testable can withstand
criticism. Logical and Methodology of Experimental Research in
The article discusses the advantages and limits of experimental eyewitness
Logical Foundations of Experimental Research:
Laboratory research in psychology has emerged from physics and
agriculture. They are in the position to create and manipulate
o By controlling the constant variables, the researcher can
systematically investigate the influence of particular factors.
o Experimental control of the researcher is limited by the fact
that the human targets of their research are themselves
distinct individuals. This it like what agriculture has to deal
with (cannot control the amount of sunlight or wind).
Not only are people different, but they can vary in
behaviour at different times. One witness may have a
better memory than others and a high motivation.
Hard to apply random assignment that guarantees that both of the
groups in the experiment are equal.
Experimental control and randomization allows for researchers
to draw conclusions about causality.
o Only experimental designs can come to causal conclusions
since they hold all other variables constant and randomly
assign subjects to experimental conditions.
Drawn on the relation between time delay and memory
Basics of Experimental Design:
Formulate a testable hypothesis that is derived from a larger
theoretical model or reflects a practical problem.
The testability of a hypothesis is restricted by practical, logical, and
o The guidelines that have been put in place have limited some
of the research that can be done through experimentation for
eyewitness accuracy. Ex. the influence of violence and life threat on
Can test hypotheses that cannot be tested in a real investigation.
Contains a statement of the association between one or more
independent variables and one or more dependent variables.
o Independent variable is manipulated by the researcher
o Dependent variable is measured and represents the effect.
Operationalization of the Independent Variables:
In order to enable a comparison the independent variable must
have at least 2 different levels or degrees.
o The decision about what these levels are is operationalizing
Interaction is when one independent variable influences another.
Constructs are complex concepts that are hard to be
Independent variables have to be operationalized in a way that
represents the construct as broadly as possible and is not
confounded (interrelated) with any other constructs.
Construct validity is achieved if operationalization of the variables
validly represents the construct that is being investigated.
o Can be achieved by conceptual replication. This is
investigating the same hypothesis in different experiments
with different operationalizations.
The subjects have to perceive the experimental procedure
according to the experimenter‟s intentions.
o Experimenters usually have a pilot test or manipulation check
to test this before the experiment is done.
Making sure that the changes in the dependent variable can only be
attributed to the changes that were made in the independent
variables and is not confounded by any other factors.
o If this is met and the results can be interpreted
unambiguously than it‟s internally valid.
Random assignment is very important. Subject Characteristics as Independent Variables:
Internal validity is evident in “quasi-experimental designs”. This
uses demographic or personality variables of the witnesses as
o Not actually an experiment since they cannot be randomly
assigned to people.
The Measurement of the Dependent Variables:
Person Description and Person Identification:
o Dependent variables also have to be operationalized in a
construct valid way. There has to be some way to measure
o In regular cases, there is no objective external criteria
available to determine the correctness of an eyewitness
report. Even using confessions as eternal criteria presents
o Can only determine that the right identification was made if a
large number of comparable cases of clearly wrong
identification are available.
o There is no simple way to establish incorrect identifications
with an objective external criterion.
o An experimenter can objectively control the correctness of an
Incorrect Identifications and the Tendency to Guess:
o Incorrect identification: the witness identifies an innocent
suspect. These are more serious errors, and can be studied
by using a target-absent line-up.
o False rejection: the actual criminal is present in the line-up
but is not recognized by the witness. You use a target-
o Accuracy of an identification is partly determined by the
witness‟ memory strength. The better their memory, the
lower the risk of error.
o Identification accuracy is also affected by the decision criteria
that the witness consciously or unconsciously applies.
This determines the minimum amount of perceived
similarity between the suspect and the witness‟ mental image of the criminal that the witness requires before
making an identification.
Some may require for the person to look exactly
how they picture them in their head while others
will identify a person at a lower level of similarity.
If their criteria is really low, it might result on the
Instructional bias lowers the decision criteria without
lowering memory strength.
o Almost impossible to separate the two in real life since it is
impossible to determine whether an identification results from
a good memory or from guessing.
o Signal detection theory has been used for the separation of
memory and guessing.
Subjects are shown a series of individuals.
New photos are then shown and subjects have to decide
whether or not they have been shown the photo before.
Their responses are influenced by their memory
strength and their decision criteria. The response
curves for both types of responses and can be
computed using math.
This has the ability to estimate the strength of memory
independent of the response criteria.
It lacks realism since there is rarely multiple criminals
for a witness to identify.
o Target-absent line-ups is when the suspect is replaced by a
similar looking substitute. This helps in computing false
alarm rates and then can be used to correct hit rates.
Incorrect Identifications in Line-Ups With and Without the Criminal:
o The foils in a target-present line-up provide information on
the probability of false alarms. It corresponds with the
likelihood of an innocent suspect being identified from the
It has been disproved based on logical reasoning.
Process Measurements: o Usually more interested in the investigation of the processes
underlying a phenomenon than in the prediction of a
o We want to know why an eyewitness has a good or bad
memory performance not just the probability of choosing the
o Use experimental designs and statistical methods to examine
Dependent variables are measured in addition to recall
and recognition variables.
Ex. weapon focus effect: the recognition of an armed
criminal would be impaired due to a shift in attention.
They used a special camera that would record the
subject‟s focus which showed that the witness would
spend more time looking at the weapon than the
offender compared to an unarmed offender.
Statistical Analysis: Reliability Versus Effect Size:
Statistical and Practical Significance:
Statistical analysis is usually applied in an experiment to:
o Ensure that the observed differences in the behaviour of the
experimental groups are attributable to independent
variable(s) instead of random variation.
o Determine the size of the effect of the independent variable.
A hypothesis is accepted if it has the probability that at least 95%
that the results are not due to random error.
o Our confidence in the results grows with the number of
observations we have made.
o The difference between groups will be more reliable the
smaller the individuals scores spread around the means.
Analysis of variance uses the mean, standard deviation, and the
number of subjects to separate the total variation of the behaviour
into random and experimental variation categories.
o Because only a limited number of variables can be held
constant in a lab setting, the individual subject‟s behaviour
will clearly vary. o Determines which portion of the total variation can be
attributed to each independent variable and their interactions.
o Parametric are linear models and nonparametric are log-linear
It is important to be able to interpret the research results properly.
o Significance level= p.
o A research result is considered statistically significant if the
p-value equals or is lower than .05.
The observed result would be obtained in only 5 out of
100 cases if only random processes were involved.
Indicates the reliability of an effect without saying
anything about its practical significance.
o Significance does not mean that a result is substantial. It just
means that it is highly unlikely that a result is due to random
The practical importance of a research finding can be
portrayed by a parameter that indicates the magnitude
of the obtained effect.
Meta-Analysis: Integration and Comparison of Research Results:
It may be difficult for a practitioner to bring their findings into line
with contradicting research findings.
Meta-analysis allows for statistical comparison between the
results of a large number of experiments.
o The size of the effect an independent variable has on some
dependent variable can be found across all known studies of
The Limits of Experimental Research in Eyewitness Psychology
Some criticism is directed against the premature application of
insufficiently proven research findings by expert witnesses in court.
Other criticism is focused on the method itself.
o Doubt that the research findings are able to provide data that
is relevant for a practitioner.
o There is a lack of realism in these experiments procedures. Researchers are interested in the examination of theories compared
to practitioners who are concerned with the analysis if individual
cases (prognosis of behaviour).
o The researchers cannot answer the specific questions that
may be presented by a practitioner. There is no way that
they would know what would happen during a specific case
but only have general observations.
Some variables are not specified quantitatively.
Uses experimental designs that are better suited to test
hypotheses instead of producing a prognosis of
Experimental research requires the reduction of a large
number of independent variables to a manageable size.
o Some variables that researchers can investigate that have
relevance for the criminal justice system are:
Estimator variables: under no one‟s control and the
effects can only be estimated. This is where the
relationship between arousal and eyewitness accuracy
fits. Since the people in the experiment have not been
personally affected by crime, it may lose some of its
generalizability and external validity.
There have been some attempts to replicate the results of labs in
more realistic settings. They have shown similar results in some,
while others have shown major discrepancies.
There is concern in increasing external validity without sacrificing
o Have to acknowledge the critical variables that distinguish the
experimental setting from real life and understand their
o Create experimental settings that combine experimental
control and internal validity with a high degree of realism.
Uninformed subjects who witness a staged crime in a
field setting. May need partial or complete deception. Exercise 1.3
Science only brings images or representations of truth.
Knowledge is the result of observation and inference (theory). It is
not just about observation.
Empirical facts that are replicable and explain theoretical
models can yield generalizations that provide a social framework
for understanding legal questions.
Psychology of law largely depends on experimental research
conducted in laboratories and field settings and non-experimental
methods like observation and surveys.
They use experimental control and random assignment of
participants to have precision and systematic manipulation in their