How is DNA Evidence Used in a Tennessee Criminal Case?

DNA evidence is one of the most powerful forensic tools available in a criminal case. Understanding how this evidence can be used and challenged is crucial for anyone facing charges in Tennessee. Continue reading and consult with a knowledgeable Memphis criminal defense attorney to schedule your free case evaluation today.

What is DNA?

DNA, or deoxyribonucleic acid, is the genetic material found in almost every cell of the human body. It carries the unique blueprint that determines an individual’s traits. Because of its unique structure, no two people (except identical twins) share the same DNA sequence.

DNA can become evidence in a criminal case when biological material is collected from a crime scene, the victim, or a suspect, and that material contains testable DNA. Common sources include blood, saliva, hair, skin cells, or semen. The sample must then be properly preserved, handled, and analyzed by forensic experts to compare it against known samples and establish a link between an individual and the crime.

How is DNA Evidence Used in a TN Criminal Case?

DNA evidence is a powerful device for the prosecution and can be used to establish a link between the defendant and the crime scene or victim. By comparing a DNA sample collected at the scene to a known sample from the suspect, prosecutors can prove beyond a reasonable doubt that the defendant was present and involved in the criminal act. In Tennessee, a match can provide compelling evidence of identity, often leading to a conviction when properly authenticated and presented.

The defense can also use DNA evidence in several ways. They can challenge the prosecution’s findings by questioning the chain of custody, the testing methodology, or the interpretation of the results. If the DNA found at the scene does not match the defendant’s, or if there is another individual’s DNA as well, the defense can use it to argue that someone else committed the crime. In some cases, the defense may request independent testing to verify or challenge the state’s forensic analysis.

DNA technology is also crucial in the review of old cases. In cold cases, DNA profiles recovered years ago can now be run through modern databases like CODIS (Combined DNA Index System) to generate new leads and identify potential suspects. DNA testing has also been instrumental in exonerating wrongfully convicted individuals. By testing evidence preserved in past cases, if the defendant’s DNA does not match the crime scene sample, it can lead to their release.

Is DNA Evidence 100% Effective?

DNA evidence is considered circumstantial, as a match only indicates a high probability, not absolute certainty, that the defendant is a match or not. This probability is based on statistical analysis, but can be inaccurate. DNA evidence can be successfully challenged in court by arguing issues such as contamination, a broken chain of custody, improper sample handling, or flawed laboratory testing procedures and interpretation of mixed samples.