In the Baton Rouge serial killer case (Derick Todd Lee, d. 1/21/16)
"...Lee was overlooked by police, because they thought the killer was white. He was linked by
DNA to the deaths of seven women in the
Baton Rouge and
Lafayette areas in Louisiana, and in 2004 was convicted, in separate trials, of the murders of Geralyn DeSoto and Charlotte Murray Pace. The Pace trial resulted in a death sentence. Newspapers have suggested Lee can be linked to other unsolved murders in the area, but the police lacked DNA evidence to prove these connections. ...Police therefore administered thousands of DNA tests to Caucasian men in and around the general area of the murders. Having no leads, police then allowed the now defunct company
DNAPrint Genomics to access DNA left at the crime scenes. DNAPrint Genomics generated an ancestry profile indicating that the suspect was 85% African,[SUP]
[5][/SUP] thus changing the course of the investigation: Police now knew they were searching for a black man ..."
https://en.wikipedia.org/wiki/Derrick_Todd_Lee
IIRC the turnaround all those years ago was only two weeks, when they paid a private outside lab. Today, what does it cost $129.95 to 23andMe while they await official lab results?