Once technology advanced, the criminal justice system began relying heavily on DNA evidence in many cases to prove guilt. The idea was that if DNA proves it, then there is no way to argue otherwise.
While DNA is very good evidence, it is not without its faults. It is possible for DNA to not tell the whole story and to incriminate someone who is not guilty. The issue with this type of evidence is the humans who collect, handle and process it.
Anyone collecting DNA must be careful. Contamination is a serious issue that can occur easily if the collector is not careful to avoid introducing any foreign matter into the sample.
Storage errors can range from contaminating the sample to losing it. Not properly labeling the sample can cause problems. There may also be mix-ups, or a sample could go missing.
The lab that processes the DNA can also introduce contaminants or mix up samples. If someone is not trained properly, they may process the sample incorrectly, resulting in errors.
DNA also is not without its faults. Since the technology is so advanced now, it can pick up microscopic DNA, which would incriminate someone who wasn’t even in the area of the crime. Trace DNA is something every person leaves behind. Someone else could pick it up without knowing, and when officials process a scene, they could pick up trace DNA of people who were never even at the scene.
Any DNA used in a criminal case must be properly vetted. It is important to ensure that everyone handling the sample did so correctly and that the sample was not just trace DNA.