Developing Analyses of Biological Evidence: Predicting Eye Color, Determining the Source of Bodily Fluids, and Locating Trace Evidence Within Guns

Several studies reported in the January 2013 Issue of Forensic Science International: Genetics are of interest for future developments in forensic evidence.

Research is being done on predicting eye color, hair color, and skin color from DNA. Currently, 37 gene sequences (SNPs or single nucleotide polymorphisms) have been identified as playing a role in these traits, and, of these, six have previously been used for predicting eye color. The current study tested additional gene sequences, beyond the previously used six SNPs, in order to test the ability to keep the cost of the test in balance with any gains in predictive value and reliability. It is important to note that these tests assign likelihoods of particular eye colors of the source person and do not provide an absolute determination of that eye color. Such tests may be used in the future to help develop possible suspect profiles.

Another type of genetic material, mRNA (messenger RNA, the “template” copy of DNA coding used for assembling specific proteins within a cell), has been found useful in determining the source of biological fluids. A study of mRNA markers identified specific markers for blood, saliva, semen, and vaginal secretions. The ability to identify the tissue source of a DNA profile would have important forensic uses because currently it is not possible to determine whether the DNA profile developed from a particular item of evidence comes from, for example, a blood droplet or from skin cells previously left on the surface of that item of evidence.

Finally, a study examined the firearms used in 20 cases of homicide or suicide in which there was a close-contact shot fired. The inside of the barrels of the guns were sterilely swabbed from the front of the weapon (making sure to avoid contact with the muzzle) in each case and also swabbed from the rear of the weapon in 16 of the cases. Usable biologic material for DNA analysis was found in 17 of the guns. Furthermore, after the initial samples were collected, each gun was fired one additional time, and usable genetic material was still found in 14 of those guns. Not only may testing of genetic material from within gun barrels be used in crime scene investigation in the future, but parameters may be developed for specific gun types such that, if biological evidence is found within the barrel of a gun, investigators will be able to determine if the firearm likely was fired from within a certain distance from the victim’s body.

History of DNA Analysis Timeline – Available Online

A DNA analysis timeline is now available on the IDS Forensic Resources website.  The timeline traces the development of forensic DNA analysis and its use by the NC State Crime Lab.  It seeks to identify what technologies were available during a particular time period.  It is a helpful tool for attorneys working on older cases or post conviction cases who need to know what techniques were being used during the time period when evidence in their case was tested.

You can access the timeline here.

Stateline and NPR report on the state of forensic science labs

In a two-part report, Stateline examines the problems facing crime labs across the country.  Part one of the series addresses recent problems plaguing crime labs and the need for judicial education regarding the reliability of forensic evidence.  Part two introduces a new forensic lab in Washington, D.C. which operates independently of state law enforcement agencies and has incorporated many of the recommendations of the 2009 National Academy of Sciences report.

You can read the part one of the Stateline report here  and part two here.

The Greg Taylor case and lab accreditation were the focus of a Nov. 20, 2012, All Things Considered report on NPR. ASCLD/LAB accredited the NC State Crime Laboratory during the time when Greg Taylor’s case was worked and still accredits the lab. In the report, defense attorney Marvin Schechter questions ASCLD/LAB’s accreditation process and calls for forensic science labs to be made independent of law enforcement.  You can listen to the story here.

Bad Science

This infographic is a good reminder that  scientists aren’t immune from pressures to exaggerate results and present false research. Anyone working on cases involving expert testimony or complex scientific evidence should keep this in mind when considering what evidence to present or what evidence to challenge.

This infographic was created by the folks at Clinical Psychology.