Sure, been watching too many cop shows? That scenario is much different than matching to a relative’s DNA. If the cops already have a DNA sample then that provides the match and they don’t have to rely on the still rather remote chance that a close relative has submitted a sample to a genealogy service that will turn up a match and that they can place the suspect anywhere near the crime without a reasonable doubt.
Possible yes, improbable yes again.
On Investigation Discovery there was a story about a woman who killed someone — her husband, I think — in a car. She was a civilian working in a government fingerprint lab. Somehow she transferred a fingerprint on file (I think Scotch tape was involved) to the car’s door handle, and framed an innocent man. Finally, it was solved. It would be so easy for nefarious to do similar with DNA.