You hear from some cold cases with a breakthrough after being left unsolved for decades, like for example: the murder has been recorded to occur in the 1940s in which back then, the perpetrator was alive committing the crime, too much time has lapsed as it’s been over 8 decades since there were any updates, the crime scene is pretty much unrecognizable now from the early photos taken by investigators in 1941.

You managed to find out the killer’s name through genetic genealogy by referencing through their living descendants alive today (contacting current living relatives of both the victim and perpetrator, to give updates on the case) confirming a match with a huge caveat: the killer has passed away 3 decades ago in a retirement home from old age never being suspected of a crime through his or her lifetime.