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How is DNA Evidence used in a Criminal Trial?

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How is DNA Evidence used in a Criminal Trial? 

Hi, this is attorney Kevin Hayslett and the question is “how is DNA evidence used in a criminal prosecution?” Well, up until the 1990s, the evidence of choice by law enforcement to place a defendant, a person charged with the crime, at the scene, with the use of fingerprint evidence, but, since the 1990s and the advancement in science, we have seen the increased use of DNA evidence. Now, what is DNA evidence? Well, DNA is something we all possess—it stands for the scientific term Deoxyribonucleic acid (DNA). Each one of us has a unique set of DNA. And when we compare the DNA found on the scene of a crime with the person accused, scientists can then conclude whether or not the DNA found on the scene matches the DNA of the accused. Now, DNA in criminal investigations is a double-edged sword because it not only helps the prosecution prove that a person was in a particular place, like a house; or that they left fingernail scrapings at the scene; or traces of their blood, semen, or hair which ties them to a particular place. Though, it also excludes people. We have seen the advent of the innocence projects, which has allowed many people who were incarcerated in state prisons or on death row become, not acquitted, but exonerated—meaning that they were let out of prison because the DNA evidence showed that they could not possibly commit the crime which they were accused. Now it’s said in DNA evidence, no two people have the same DNA—with the exception of identical twins. What government and law enforcement have done is use DNA in criminal investigations to tie a person to a particular place. 

What’s an example of DNA evidence we might leave at a crime scene? Well, generally, DNA evidence is collected through hair, blood, or semen. They are able to take blood left at a crime scene or semen in a rape case, or hair that is left in a particular place and tie that evidence to a particular individual. Now it doesn’t tell us whether or not the person committed a crime, but what it does tell us is whether that person was at a particular place. And by placing the defendant at the scene of the crime, it becomes additional evidence the government can use to show the defendant committed the crime. 

So, DNA in court is scientific evidence which is unique to each individual that scientifically can show that a person was at a particular place, not at a particular time, but at a place based on their evidence—blood, hair, or semen—at a crime scene, tying an individual to the scene of a crime. That’s how DNA evidence is used in criminal prosecution.


The criminal defense attorneys at Carlson, Meissner, Hart & Hayslett, P.A. are fighting for our clients rights in criminal defense cases in ClearwaterTampaBradentonSpring Hill, Pinellas, Pasco, New Port Richey, Manatee, Hillsborough and Hernando Counties in Florida.

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J. Kevin Hayslett

Kevin Hayslett, Esq.

J. Kevin Hayslettis an attorney practicing in the areas of Criminal Defense and DUI Defense from the Clearwater office and Hillsborough office. Kevin is an avid tennis player and is currently nationally rated in singles and doubles. You can follow Kevin onGoogle+, oron Radio IO on his show, "Kevin's Law". Kevin can also be heard on the Sirius Satellite Radio show during the "Ask the Lawyer" segment, which can be heard the first Thursday of every month.