Texas went on-line in 1998 and in the first month had two cold hits involving the same individual. Refer to our felon profiling section for more information on ReliaGene's services in this area. Return to the top . The two major concerns in handling potential DNA evidence are degradation and contamination. Degradation can be brought about by overexposure to heat and humidity.
Contamination can either be sample to sample or person to sample.
Degradation is usually caused when bacteria, mold and mildew grow on a sample. This can lead to inconclusive results. Contamination can lead to false or un-interpretable results. This happens because the PCR reaction will preferentially work on fresh DNA over older samples. So, even if a small amount of fresh DNA comes into contact with a crime scene sample that has been exposed to the environment , it is possible for that fresh DNA to give results along with or instead of the crime scene sample.