The use of DNA in criminal cases may make an important difference when it comes to establishing whether someone is guilty or not of committing a crime. Since law enforcement can gather DNA from just about anything from saliva to skin cells, police may look for DNA anywhere in a crime scene.
However, the widespread gathering of DNA is not always productive to a criminal case. It might even prove misleading when establishing guilt or innocence.
The relevance of DNA evidence
To take an example, criminal investigators may look over a murder scene. They discover a small pool of blood near where the victim had died. Law enforcement takes a sample of the blood and tests it. They find that it belongs to an individual suspected of the murder. There is clear relevance for the pool of blood since it was at the crime scene and close to the victim.
According to an NPR report, while police may find DNA samples from all over a crime scene, some of these samples might not have any relevance to the crime. For instance, police may discover skin cells on a doorknob, but investigators may not find any connection to a crime. As a result, they will probably not present the evidence at trial.
Context is important
It is not enough just to find DNA at a crime scene. Prosecutors must establish that the DNA is relevant to the crime committed. It is possible for multiple parties to pass in and out of a location and leave their DNA behind, all at times before the crime had occurred.
Individuals accused of a crime might use the location of their DNA to show that they were engaging in normal business at the time and had no involvement in the crime. Additionally, a defendant may arrange an investigation of a crime scene to locate any DNA evidence that could help refute criminal charges.