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Anthony McCartney, Associated Press
Judy Huth, left, appears at a press conference with attorney Gloria Allred outside the Los Angeles Police Department's Wilshire Division station Friday Dec. 5, 2014. Allred announced that they have met with Los Angeles police detectives to open a formal investigation into claims Bill Cosby molested Huth when she was 15 years old in a bedroom of the Playboy Mansion.

LOS ANGELES — Legal experts say any case centering on decades-old allegations against Bill Cosby would face hurdles.

In recent weeks, the comedian has seen a flurry of old sexual assault allegations, a lawsuit and a police investigation into a molestation claim. The 77-year-old Cosby settled the only sexual assault case filed against him years ago.

Civil litigation lawyers say witnesses' memories fade, witnesses may have died, or physical evidence is lacking to support the allegations. As one put it: "There's no smoking gun."

Cosby attorney Marty Singer has denied many of the claims. In one filing, Singer says the accuser attempted to extort $250,000 from Cosby in return for her silence and unsuccessfully tried years ago to sell her story to a tabloid.

Anthony McCartney can be reached at http://twitter.com/mccartneyAP