February 6, 2014

This seminar was from one of Principal Forensic Services’ forensic biologists, Julie Allard, who specialises in body fluids and their potential to provide DNA profiles for use in a criminal investigation. The types of body fluids discussed included blood, semen and saliva, all of which have presumptive tests for their detection:

• Blood – Leucomalachite Green (LMG) test
• Semen – Acid phosphatase test
• Saliva – Phadebas test

These tests produce a colour change indicating the presence of the body fluid in question, and can be used on different materials including clothes and weapons. Once areas presumed to contain these body fluids have been identified, samples can be sent for DNA profiling. This is where it starts to get a bit tricky, not only can different levels of interpretation be addressed in relation to the DNA evidence obtained, the DNA evidence itself can be troublesome! For example, is there enough DNA present to produce a profile? Is there a mixture of two or more people’s DNA present? Has the DNA profile come from the body fluid in question? Whose DNA and therefore body fluid is present in the sample? Can the presence of a given person’s DNA determine the actions of that individual?

Julie emphasised the importance to take the context of the case into account when answering these questions. A forensic scientist may address the activity level of the evidence, e.g. Person A kicked Person B but must not address the question of whether or not a person committed a crime or not, since this is the job of the jury. The CAI (case assessment and interpretation) model aids a forensic scientist in evaluating the evidence they are given in a balanced, logical, robust and transparent manner.

However, the interpretation of evidence for use in court is a contentious subject, Julie pointed out that as new information arises concerning a case, the evidence must be re-evaluated in light of this new information. Furthermore, it is likely that the information that the prosecution scientist has received does not correlate with the information received by the defence scientist, leading to much disagreement between experts!

Finally, for forensic scientists to effectively use the CAI model to clearly show how a given conclusion was derived from the evidence provided, in light of the case information, Julie stressed that the logical assessment and interpretation steps need to be based upon empirical data that mimics the forensic context.

www.principalforensicservices.com

The annual meeting of the American Academy of Forensic Sciences is currently underway in Seattle. Dr Morgan will be in attendance, accompanied by a group of CFS doctoral students who will be presenting their research.

Helen Earwaker will be presenting her poster titled “Fingermark Submission Decision Making Within a United Kingdom Fingerprint Laboratory: Do Experts Get What They Need?”
Criminalistics Poster Session [Wednesday]

Georgia McCulloch’s presentation is entitled “Is High Performance Liquid Chromatography (HPLC) a Useful Addition to Current Geo-Forensic Analytical Techniques?”
Criminalistics Session II [Thursday 1:30pm]

Michaela Regan will be presenting her poster, titled “A Study to Determine the Use of Gunshot Residue Upon Clothing as an Item of Evidence”
General Poster Session [Wednesday]

Sherry Nakhaeizadeh will be giving a presentation on “Cognitive Bias in Forensic Anthropology: Visual Assessments of Skeletal Remains Are Susceptible to Confirmation Bias”
Physical Anthropology [Friday 12:00pm]

Dagmar Heinrich’s presentation is entitled “A “Realistic” Study of Sharp Force Trauma Recognition in Burned Remains: The Forensic Implications”
Physical Anthropology [Saturday 12:15]