While DNA is an amazing tool within the criminal justice system, it is not without its fault. It is possible for DNA evidence to not be accurate.
The US Department of Justice explains there are many situations in which DNA evidence could become corrupt. Typically, this is due to human error.
When handling DNA evidence, humans can create problems. Improper storage could introduce contaminants that will jeopardize the sample. It could also lead to losing a sample or cause issues with multiple samples becoming mixed up.
Collection problems can lead to many issues. If not collected properly, a sample may be unusable. It could also add in DNA that is not part of the actual crime scene. Mislabeling can also cause problems with the sample, making it unusable in court.
There are even more issues that could happen in the laboratory when processing the samples. Many errors could be due to improperly trained technicians who do not know how to correctly process the sample. Technicians, even those with experience, could introduce contamination or identification issues with samples as well.
While the DNA itself is solid evidence, there is always the chance a sample could become corrupt throughout the process from collection to lab processing. What the court gets may not always be a good sample. It is possible for errors in the sample or the process to alter the DNA. Tracking the sample from the scene to the courtroom is an essential part of ensuring no mishandling occurs. It is also important to verify who touched the sample and worked with it to rule out possible issues before the DNA is evidence in a case, especially if the other evidence does not match up with it.