Anthro Notes Oct. 11/12
- The impact of DNA on individuation from bone and teeth: DNA can be used for individuation of
skeletal remains. It is no longer slow and it is not nearly as costly. DNA is found in the lacunae when
cells degrade and in the dentin and pulp line of teeth. DNA offers the ability to determine sex of
immatures and adults without hip bones via the amelogenin locus on the X and Y chromosomes. The
amelogenin gene is the gene located on the X and Y chromosomes that codes for proteins found in
tooth enamel. This locus is dimorphic between sexes and can be used to determine sex. mtDNA and Y
chromosome haplotypes can be used for ancestry. Because of the power of DNA, many have
questioned whether forensic anthropology is relevant today.
- Forensic anthropology and DNA analysis: Is individuating skeletal remains still relevant in the age of
DNA? There are a number of reasons why doing an osteobiography is relevant 1. DNA may not
always be preserved and even if it is, there could be allelic dropout. 2. Nuclear and mitochondrial
DNA can build a genetic profile but it cannot build biological profile, which is important to reduce the
potential matches so that a reasonable number of comparative genetic samples can be obtained. 3.
The differences between biological and genetic profiles are particularly important when comparative
DNA is lacking. 4. In situations of co-mingled remains (mass disasters), the anthropologists can
associate parts of the skeleton to make the expensive DNA processing more efficient. 5. All data are
circumstantial, so as much information that can be generated as possible will help solve cases. Even
class traits such as tire marks can narrow down the list of suspects(the chances of a person having
two matching class traits to a crime are very low).
- Forensic anthropology today: Though individuating human skeletal remains is still important today,
Dirkmatt et al note that the field has changed significantly due to two external and four internal
influences. If forensic anthropology was to remain relevant, it had to shift from mere identification to
a larger range of problems.
- Procedures and methods for forensic casework: Everything begins at the crime scene and different
specialists have different skills. In order for an evidentiary item to have probative value relative to an
exemplar sample, you must establish context and continuity. Continuity begins at the crime scene
and ends in court. You must always assume a case will go to court. Each technique has its own
approaches to individuation (qualitative vs. quantitative assessment). Quantitative is probabilistic
science and has a numerical component. All primary evidence is circumstantial, even DNA.
- Forensic science error rates from newly established proficiency tests can be high. For spectrographic
voice identification, the error rate (false positives) can be up to 63%, and depends on the type of
voice tested. Handwriting has error rates 40-100% (peoples handwriting can change). Hair
microscopy is 12%, even when mtDNA is used as the control. Bite marks are up to 64%. It is still
used, but the focus is now DNA recovery from saliva. Fingerprints are 4-5%. The error rate of mtDNA
is 0% if at least 9 STRs are used. A six STR DNA profile obtained from a crime scene matched a
database profile of a convicted offender, but this person was later found innocent when further STRs
- Expert witness testimony: Our system, like Britain and the US, is adversarial. Under Daubert, there
are new criteria for admissibility. The judge is the gatekeeper (all evidence goes through him). In
Canada, only in those provinces with a coroner system does an expert witness other than a forensic
pathologist provide court evidence.- Adversarial: Legally-trained minds value testimonial evidence and trust vigorous cross-examination
to expose its weaknesses. Many lawyers feel that richer parties in litigation can purchase science and
sell it in the courtroom without the jury being aware. There is the CSI effect in court, which is the
pressure to do more tests. You must know what tests are relevant to the case (this is Mohan comes
- Lawyer speak and science speak are very different. Scientist vocabulary (lawyer vocabulary)
reasonable certainty (inexact science), probability (possibility), hypothesis (theory), finding
(opinion), test (experiment), apparatus (toy/bag of tricks), polygraph (truth box), calculation
(conjure up), consultant (paid employee), estimate of probability (speculation), expert opinion
- Expert witness testimony from Daubert/Mohan recommendations and rules of engagement: 1.
Continuity of known (exemplar) and unknown (evidentiary) samples. 2. Disclosure (the scientific
paper trail). 3. The qualifications of the expert (papers, courses, professional associations). 4.
Presenting evidence in court (must be careful how you present it). 5. Voir dires. 6. Reliability of the
laboratory (mtDNA is more susceptible to contamination in modern samples because of high copy
number) and the expert. 7. The meaning of statistics. 8. The significance of the evidence in a
particular case (scientific vs. other).
- R. vs. Mohan in Canada: There are four criteria upon which the admission of expert evidence depends
1. Relevance (science, cost benefit analysis). This was important in the second voir dire on mtDNA
in R. vs. Woodcock. 2. Necessity in assisting the trier of fact. 3. The absence of any exclusionary rule.
4. Properly qualified expert.
- Issues whenever science is used in courts: Admissibility (voir dires reviewed by judge not jury).
Chain of custody. Relative weight given to the evidence once it is submitted. Qualitative (discernible
uniqueness assume its unique, but have no probative way of testing it) versus quanti