Most people believe DNA is the most concrete type of evidence in a criminal case. Hollywood would have you believe that if the prosecutor has DNA evidence, then there is no fighting the charges because DNA does not lie.
This is not entirely true. According to National Geographic, DNA is not infallible.
Factors can influence
One of the reasons why DNA can end up not being good evidence is there are many factors that must align to ensure accuracy. At the crime scene, investigators must collect the DNA sample properly. It must travel in proper storage. In the lab, the workers must process it properly. Finally, whoever is interpreting the results must do it correctly. There are many opportunities for mistakes to enter the process.
Another issue with DNA is it only shows someone was present. It cannot show what that person was doing when they left their DNA. Even worse, there is no knowing when the person left the DNA.
This is a huge issue as it could easily implicate someone in a crime simply because that person was in the area of a crime at some point. Because the processes are so advanced now, it is possible for an incredibly small amount of DNA, even trace DNA, to remain behind and end up collected as part of a crime scene investigation.
While DNA technology has had amazing advancements, that does not mean mistakes will not happen. There are still many things that could go wrong. It is essential in criminal cases that juries understand the issues associated with DNA evidence, especially if there is any doubt as to the validity of the samples in the case.