Cosby was in New York on the night that model Chloe Goins claims the comedian drugged and accosted her in a bedroom of the mansion, attorney Martin D Singer wrote in a statement.
Singer said he would present evidence to authorities detailing Cosby's whereabouts before, during and after the Playboy Mansion event.
Goins met with Los Angeles police detectives on Wednesday, and her attorney said the incident took place during an event in August 2008. While many of the abuse claims leveled against Cosby fall outside civil and criminal statutes of limitations, Goins' allegations may fall within the time period that Cosby could be charged.
More than 15 women have accused Cosby of drugging them and sexual abuse, which has led to the cancellation of the comedian's projects at NBC and Netflix. He continues to perform stand-up comedy shows.
Goins' attorney Spencer Kuvin said Wednesday that the alleged abuse occurred during an event called "Midsummer's Night Dream Party" on Aug. 9, 2008, at the mansion. Goins says she does not know what happened while she was blacked out, but Kuvin has said she awoke to find herself naked and Cosby over her.
"Mr. Cosby was in New York on that date," Singer wrote. "We will be providing documentary evidence to the appropriate authorities which conclusively establishes Mr. Cosby's whereabouts on August 9th and for the preceding and succeeding days."
In response to Singer's statement, Kuvin wrote in an email: "We look forward to seeing this alleged proof."
Los Angeles prosecutors will make the final determination on whether Cosby will face criminal charges based on Goins' allegations.
Singer has denied some but not all of the allegations against Cosby, and the comedian joked about the scandal at a recent show in Canada.
On Friday, NBC Entertainment Chairman Bob Greenblatt closed the door on the network collaborating with Cosby on any future projects, noting the number of accusers who have come forward.
Although none of the accusations against Cosby have been proven in court, Greenblatt said, "when that many people come out and have such similar complaints, it became a tainted situation" and the network didn't want to proceed with a new sitcom featuring the comedian.