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Grim Sleeper arrest marks big advance for controversial DNA evidence

July 10, 2010 |  2:43 pm

Frustrated by their inability to find the notorious killer known as the Grim Sleeper, whose DNA was not in a law enforcement database, Los Angeles police this spring asked the state to look for a DNA profile similar enough to be a possible relative of the killer.

In April, state computers produced a list of 200 genetic profiles of people in the database who might be related to the alleged serial killer. Among the top five ranked as the most likely relatives was a profile that shared a common genetic marker with the crime-scene DNA at each of 15 locations that the crime lab examined.

Scientists knew that a profile with that sort of matching pattern indicated a parent-child relationship.

To winnow the candidates further, and knowing that their suspect had to be a man, they tested the DNA of the 200 offenders whose profiles resembled the crime-scene DNA to determine if any appeared to share the Y chromosome, which boys inherit from their fathers.

There was one match, and it was the same profile that had shared all 15 markers on the first round of testing.

Excitement swept the room at the state DNA laboratory in Richmond where the match was made. Jill Spriggs, chief of the state's Bureau of Forensic Services, recalls a feeling of "amazement" when she learned of the breakthrough: The two rounds of tests almost certainly had located a son of the suspect -- the first high-profile U.S. case cracked by a technique known as familial DNA searching.

Click here to read Maura Dolan's story on the DNA evidence used in the Grim Sleeper case. 

In the video below, Jason Felch talks about how DNA was used in the Grim Sleeper case.

RELATED: THE PROMISE AND PERIL OF DNA EVIDENCE: Check out Dolan's and Felch's investigation about the growing use of DNA evidence in the courtroom. Read the entire series, plus photos, graphics and more.