Why DNA is not Foolproof

DNA Evidence

To be fair, DNA evidence would go down in history as one the most influential technologies by the criminal justice system. However, its much-touted “infallibility” is falling like a pack of cards in the face of growing technological scrutiny.

dna evidence

DNA Evidence is Fallible

For the layman, the premise of using DNA evidence is fail-safe. Our DNA is one of a limited number of biological signatures—another being our fingerprints. Considering that on average we shed 30,000 and 40,000 skin cells per hour, it is overwhelmingly possible for a suspect to leave a bio-trail at the scene of a crime that makes identifying him or her remarkably easy.

However, that explanation is also the bedrock of the opposing viewpoint held by professionals—that DNA evidence is easily transferable. Especially in instances where the DNA evidence is culled from skin cells, then the ability of skin cells to move easily can be a limiting factor to the reliability of the technique. Take this illuminating scenario for example. The murder of a multimillionaire was pinned on a homeless man. Unfortunately, this was a false allegation. The paramedics that had aided the homeless man earlier in the night also dutifully went to the murder scene. The cells of the homeless man had inadvertently tagged along for a road trip on the uniforms of the paramedics to the murder scene. This is one of the rising instances where the consequences of using DNA evidence have had negative impacts on the criminal justice system.

Touch DNA and how it affects the Criminal Justice System

The term to describe the ability of skin cells to implant themselves on objects is Touch DNA. The aging conception that DNA stays in one place is not holding up against growing evidence. In fact, according to a study published in the International Journal of Legal Medicine, it is possible for individual A to shake individual B, then when individual A touches an object afterward, individual A deposits the skin cells of individual B (acquired during the shake) rather than those of individual A on the object. According to another study in the Journal of Forensic Sciences, this type of transference could be the sole reason why individual B may be adjudged the main contributor to the DNA pool found on the object, despite never touching the object. The explanation for this phenomenon is that individuals shed skin cells at varying rates. A person who sheds more skin cells with invariably has a stronger DNA presence after analysis in a laboratory.

The New Dimension of DNA Evidence in Criminal Defense

For a while, prosecutors gleaned cheerfully after the discovery of DNA evidence. Going forward, this initial enthusiasm will grow thinner as more research defines the boundaries of the credibility of DNA evidence. For now though, the seed of skepticism has been sown. Touch DNA no longer primarily means clean-cut cases. DNA evidence is not always right, and in criminal defense that could be the difference between an acquittal and incarceration.