Forensic DNA Database

In the previous chapters we learned about how DNA is extracted using different methods and how its PCR amplification and STR typing is done. We receive results of these methods in the form of an electropherogram—which gives us the details about STR polymorphisms present in the DNA of a particular sample. If we have different samples, for example, the blood of a suspect and the blood and tissues recovered from underneath the fingernails of the victim, we can simply extract and profile the DNA from both the samples and compare them to find out whether they belong to the same individual. However, in certain cases, we do get the perpetrator DNA, but without anything to compare it with. In the same case as above, if the police do not have a suspect pool, any DNA profile generated from the tissue recovered from victim’s fingernails will have to be stored until a suspect is identified. Thus, the first DNA databases were created, which were essentially repositories of DNA of convicted criminals, and were used as tools to assist law enforcement individuals in solving crimes. Whenever any unknown biological sample was recovered by the law enforcement agencies, its DNA was profiled and compared with the profiles present in the DNA database.