Keith Willis (alias Durvo) is a local Eastern European drunk with a mental state rotted from years of alcohol poisoning. Willis was a paid accomplice of Nicky Pratt and Doug Waverly, having lured Canadian gang-rape victim Jennifer Durning with a ruse of "having" her passport so Waverly and Pratt could abduct her in their car and murder her. Williss also went back to her hotel room and stole her coat to remove evidence, leaving a pubic hair on the toilet when using the bathroom there.
The Special Victims Unit tracks him down, but "Durvo" isn't a credible witness to testify. He's either released or checked into a facility to either treat his alcoholism or take care of him and his dementia. (SVU: "Gone")