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The pitfalls of trace DNA evidence

On Behalf of | Feb 6, 2024 | Criminal Defense |

Advances in science have given investigators and prosecutors a lot of new tools over the years that can be used to put evidence in front of juries – but few things are so compelling to juries as evidence that contains genetic material (DNA). Today, even the smallest amounts of genetic material – in quantities too small to even be seen by the naked eye – can be tested.

Unfortunately, this “trace DNA” can give misleading results that can be problematic in criminal cases.

What is trace DNA?

Trace DNA, also known as touch DNA, refers to the small amounts of genetic material left behind when individuals come into contact with surfaces or objects. This genetic material can include skin cells, hair follicles, saliva or other bodily fluids. Unlike traditional DNA samples, which are usually obtained from blood or semen, trace DNA can be incredibly minuscule and challenging to detect.

How can trace DNA be wrong?

Forensic scientists often use trace DNA to link individuals to violent crime scenes. The presence of even a few cells can potentially establish a connection between a person and a specific location, object or victim. Here is why that’s potentially a problem:

  • Transferability: Trace DNA is highly susceptible to secondary transfers, which means it can end up in places that its donor never visited.
  • Contamination: Because samples are so small, even the slightest cross-contamination during collection, handling or analysis in a lab can lead to erroneous results.
  • Degradation: The tiny quantity of DNA involved can be susceptible to degradation due to sunlight exposure, humidity and temperature fluctuations, all of which can lead to inaccurate results.
  • Nonstandard procedures: Trace DNA analysis procedures can vary from lab to lab, and interpretations can vary of what is found. There are fewer standard practices in trace DNA analysis than with traditional processes.

It is so important for people to realize that DNA is definitely not the “sure thing” that it is often portrayed to be in popular culture. If you or a loved one has been accused of a violent crime based on trace DNA, it is wise to explore all the defense options you may have available to you.