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Tampa Criminal Lawyers: What does “contamination” mean with DNA?

Tampa criminal lawyers are often asked about DNA contamination in cases involving DNA evidence.  Anyone that has watched any criminal drama on television has noticed in the last 15 years, no show is complete without involving DNA evidence in some form or capacity.   It is worth mentioning that DNA collection has evolved beyond simply the collection of DNA from blood and semen, the majority of current cases involve “touch DNA”.  We discuss “touch DNA” elsewhere in our Tampa criminal lawyer blog, but it is essentially the DNA left from someone touching something.

The use of DNA evidence and experts has expanded significantly in its use in Florida state courts.  This is especially true in cases involving violent felonies. As a Tampa criminal lawyer, this has caused us to evolve and evaluate DNA evidence more closely and from a more scientific stand point since juries now rely on it so significantly. At Stetson University College of Law, I had the opportunity to take specific classes regarding technology, science, and their impact on the criminal justice process. The overwhelming majority of the class dealt directly with the collection, analysis, and use of DNA.  More importantly, it provided us the scientific background to successfully challenge DNA collection.

In DNA cases, the most common form of abuse or negligence currently appears to be contamination issues. Contamination occurs when a foreign DNA sample is introduced into the sample collected from a crime scene. The easiest way to think of these situations occurring when a DNA sample taken at a crime scene consists of A and B.  The lab technician testing the material has a DNA of C, if the lab technician’s DNA mixes with the sample from the crime scene, the new sample will consist of A, B, C. This is certainly simplified version, but it illustrates the clear dangers of contamination. As you are aware, DNA evidence more often than not doesn’t identify a specific person rather it provides a probability and/or exclusion. When contamination occurs the probability is skewed significantly because foreign samples are introduced into a known sample. It also obviously eliminates the ability of the merged/contaminated sample to exclude people.  You can clearly understand where this would certainly play a big factor in a criminal case.

This is especially concerning because juries, due to television dramas, believe DNA is an infallible science. This is simply far from the truth. DNA evidence can be as skewed and as unreliable as eye-witnesses, confessions, etc. DNA evidence relies on highly specialized collection and identification procedures which have severe limitations. It is critical if you are involved in a case involving DNA evidence you have an attorney that understands the scientific collection of DNA and that DNA is simply not the end of a criminal case. Frankly it is simply another tool in a criminal case for both defense attorneys and prosecutors. As Jose Baez from the Casey Anthony trial called scientific evidence, “the fallacy of forensics.” When used improperly, scientific evidence like DNA can be manipulated and driven by prosecutors or defense attorneys to look and tell a story just like anything else.

If you were someone you know has questions concerning DNA in their criminal case, contact the Tampa criminal lawyers of Hackworth Law for a free case consultation. Our Tampa criminal lawyers have handled a wide variety of cases involving scientific evidence ranging from DNA to fingerprints to breathalyzers and all forms of scientific evidence in between.  If you would like to contact one of our Tampa criminal lawyers immediately, please use the “contact us now” tab in the upper right hand corner of our website.  We appreciate you checking out our Tampa criminal lawyer blog and look forward to hearing from you.