A Little More About DNA and Criminal Investigations

DNA testing as used in criminal investigations is very similar to the use of fingerprints and the testing for alcohol consumption. In the United States, there is a long line of court cases challenging all three types of tests. Subsequently, because of the court decisions, there are rules that criminal investigative agencies must follow when using any of the three types of evidence in court. Those rules are fairly strict and any deviation from the rules may cause the criminal prosecutors to lose their case and allow the suspect to go free.

The current plethora of criminal investigation TV series would lead you to believe that the investigative agencies merely have to gather the "evidence" to have criminals convicted. These shows portray the investigative agencies as "solving" the crimes in the same way that detective shows used to do so in the past. Matching fingerprints, producing an alcohol test or matching DNA does not automatically produce a criminal conviction. For example, if you refuse to take a sobriety test, in most U.S. jurisdictions, you could suffer some severe consequences.

Now, what could happen if you take a genealogically motivated DNA test? Well, if you are criminal, it would be the same as voluntarily giving your fingerprints to a law enforcement agency. So, if you plan on becoming a criminal, providing a DNA test falls into the same category.

As I sort-of explained in my last post, even if you voluntarily give a DNA sample to a genealogy company, there is really no practical way the sample and the testing results could be used in a criminal prosecution absent another test done by the investigative agency that showed you were the one submitting the test. The reason is that when the genealogy DNA test is administered, there are no procedural controls over the way the test is conducted. You could have submitted someone else's DNA or even the DNA from your dog or cat. Of course, you might also have done the test correctly and the sample really is you. But that would have to be proven in a court of law.

At best, an investigative agency might be able to use a matching DNA test from a genealogy company to make you a suspect in an investigation. But it is unlikely that the genealogical test alone would help to establish your guilt or innocence. It is much more likely that a criminal would have left some other sample of their DNA at a crime scene that would be used with a properly obtained sample after arrest than that the DNA would be used from a genealogy test.