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University of New Hampshire Designs a Simpler, Cost-Effective Test to Identify Touch DNA

by Jo Ellen Knott

DNA profiling has become the gold standard in forensic science since the first murder case was solved in England in 1987 by genetics professor Alec Jeffreys at the University of Leicester.   Although Colin Pitchfork is not as notorious as Charles Manson or Jeffrey Dahmer, it is a name forensic scientists know well for being the first criminal to be convicted of murder using DNA evidence.

A recent study by researchers at the University of New Hampshire (“UNH”) published in the Journal of Forensic Sciences continues the foundational work of Jeffreys and offers a simpler and cheaper method for identifying touch DNA. The study led by Samantha Crane, co-director of the FAIR Lab at UNH, and co-authored by anthropologist Connie Mulligan at the University of Florida will help advance the impact DNA profiling has in forensic investigations.

Traditional DNA testing can be expensive and complex, hindering the ability to distinguish between DNA left by a perpetrator (primary transfer) and DNA transferred indirectly from another source (secondary or tertiary transfer). However, a new method developed by the UNH researchers led by McCrane utilizes a more accessible and affordable technique called qPCR.

To test the method, the researchers had volunteers transfer touch DNA to various objects in a controlled setting. Male and female volunteers first touched a gun grip, then the female volunteer touched a coffee cup. The researchers swabbed the gun grip, the coffee cup, and the female volunteer’s hand for DNA. The results showed a 71 percent success rate in identifying the male’s DNA on the gun grip (primary transfer), a 50 percent success rate in finding the male’s DNA on the female’s hand (secondary transfer), and a 27 percent success rate of finding the male’s DNA on the coffee cup (tertiary transfer).

“The challenge with transfer DNA is that it opens up the dangerous possibility of DNA ending up on items or victims at a crime scene that a person may not have touched,” said McCrane. She warned, “This has occurred in multiple cases, leading to innocent individuals being charged for crimes they didn’t commit.” Crane’s new method offers a more cost-effective way to analyze touch DNA, potentially preventing wrongful convictions.

The UNH study also explored how factors like age, ethnicity, and skin conditions might influence DNA transfer. The researchers found that ethnicity and age did not seem to affect the transfer of touch DNA. However, due to the limited sample size, they could not draw definitive conclusions about the impact of skin conditions.

According to McCrane, more research is needed to fully understand the variables affecting DNA transfer. This new, simpler method could lead to more extensive studies with larger sample sizes, ultimately improving our understanding of touch DNA and strengthening forensic investigations.

 

Source: Chemical and Engineering News

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