LE doesn’t get a ’person’s’ DNA from these websites, they compare a DNA profile with other DNA profiles in the database.
So someone in curious and submits their DNA to a database- 23nMe or ancestry etc. These are Familial DNA Databases
Somewhere body fluid or hair has been collected from a crime scene. They extract the DNA from the fluid or hair. A DNA profile is created.
This evidence could be collected yesterday, or 30 years ago.
First they would compare this DNA profile to a Criminal database.
Maybe there are other cases elsewhere that contain DNA that has the same profile, so they know there is a serial perp and have his DNA Profile. They don’t know who he is.
The identity happens when the DNA profile is linked to a person’s name.
So, if they do not get a match to Criminal databases, they can compare to Familia databases.
If there is a match it can be very confusing to figure out who the actual individual person may be. The markers in common could be in common with hundreds or thousands of people. Think of it like linking you to your great great great grandparent- or even more greats. All of the people who are descended from them have those markers. So who is it?
It takes more work from there to eliminate and figure it out- sex, age, location,
Imagine getting it down to several male cousins then brothers.
The 1979 case of a murdered 18-year-old baffled local police officers for decades, until they got a break from evidence Michelle Martinko left behind.
www.cbsnews.com
The last time I checked there was a legal issue with Yogurt Shoppe Murders Dec 1991 Austin Texas. While a connection has been made from DNA found at the scene to a database in Florida- that database is not legally able to give out the family lines who are connected. People giving their DNA for a study did not sign that it could be used to compare for forensic purposes.
The 1991 murder of four teenage girls in a Texas yogurt shop remains unsolved, but there's hope that advancing DNA technology will change that.
www.cbsnews.com