I wrote the short piece below to give laypeople a simple non-technical explanation of how DNA might work in a case like the Colonial Parkway Murders. Do you think this does the job?
Thanks.
Bill Thomas
So how does this DNA thing work anyway?
The Colonial Parkway Murders families have been told by law enforcement (FBI and Virginia State Police) that they may have perpetrator DNA in 3 of the 4 crime scenes in the unsolved Colonial Parkway Murders. If the DNA samples are clean enough, they can be run in the national CODIS database, which contains DNA profiles from persons convicted of certain crimes. The challenge is when a potential perpetrator has never been arrested, charged and convicted of the type of crime, which would require his or her DNA profile to be put into the CODIS database. There is no national database of citizen DNA profiles.
Recently, law enforcement investigators, forensic experts and genealogists worked together to identify a suspect in the Golden State Killer case, which stretches back more than 40 years. Investigators took a DNA sample from the unknown suspect in the Golden State Killer case and loaded the profile into GEDmatch, an open source website which allows DNA profiles to be used for research and law enforcement purposes. The experts found a match to a distant relative of the suspect on GEDmatch. Then a team law enforcement and genealogists spent many hours building an extended family tree for the matching DNA profile in order to identify possible suspects.
After extensive research, the team was able to identify a potential perpetrator. Law enforcement then put the suspect under surveillance, looking for an opportunity to capture his DNA to confirm they had the right man. After the suspect went into a Hobby Lobby store near his home in California, agents took a DNA sample from his car door handle. Forensics experts confirmed that the touch DNA matched DNA evidence left at one of the crime scenes in the Golden State Killer case. In an abundance of caution, law enforcement continued to watch the man's home until they were able to collect a second sample from his trash, a discarded tissue. Tests confirmed a second DNA match, and law enforcement moved in to make an arrest.
These techniques have now been used to make several other arrests in cold cases around the country, and there is great hope that they might be helpful in cases like the Colonial Parkway Murders and other unsolved cases where there is DNA evidence.
Bill Thomas
Brother of Cathy Thomas
Colonial Parkway Murders