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Former Bill Cosby prosecutor: Deposition could support new charges

The prosecutor who investigated allegations that Cosby drugged and sexually assaulted a woman believes there's an opening for new charges against the comedian.

The prosecutor who investigated allegations that Bill Cosby drugged and sexually assaulted Andrea Constand in 2004 says he is not surprised by new revelations that the embattled comedian admitted to acquiring sedatives to use on women. But Bruce Castor, the former district attorney for Montgomery County, Pennsylvania, believes the deposition released on Monday could support criminal perjury charges against Cosby.

Castor, who oversaw a 2005 investigation that did not result in charges against Cosby, said the newly released testimony adds a detail that supports his suspicions about Cosby.

RELATED: Cosby's lawyers fought to keep docs sealed

“It adds the specific drug -- we always suspected that he had drugged her -- but we couldn’t prove it, so it adds what the specific drug was,” Castor told msnbc Tuesday in an interview. Cosby admits to acquiring Quaaludes in the newly released deposition.

That admission is relevant to prosecutors’ analysis of his “criminal intent,” Castor said, and it matches the theory his office pursued. “The problem with theories is, you can’t arrest on a theory,” he said, “you have to prove you’re theory is right -- and we were unable to do that.”

The sealed transcript “was not available to any prosecutor all these years,” Castor lamented, and he said Cosby did not make the same admission when speaking to Castor’s investigators.

Cosby's lawyers had fought the documents’ release, saying it would be “terribly embarrassing.” More than a dozen women have accused Cosby of sexual assault. The comedian has never been charged and denies the allegations.

While most of the sexual assault allegations against Cosby are simply too old to prosecute, barred by state statute of limitations laws, Castor believes the deposition itself could provide the basis for new criminal charges against Cosby.

“I can tear that deposition apart,” Castor said, “and anything that I can prove is a material lie would still be subject to a perjury investigation and prosecution.” Perjury is a third-degree felony in Pennsylvania, punishable by up to seven years in prison.

Castor is not simply speaking as an observer or former officeholder – he is currently a candidate for his old D.A. job. 

RELATED: From the archives: Cosby controversy

He began campaigning in January, and has won his past four elections, most recently for his current post as Montgomery County commissioner.  

While judges are barred from discussing specific cases during campaigns, Castor said he is free to specifically outline a new case against Cosby. 

Referring to a new perjury investigation, Castor said “that’s what I would do, given the opportunity.” His legal theory is that because any potential perjury in Cosby’s deposition was sealed and unavailable, the clock for charging it should only begin this week.

“Most people would think the statute of limitations has run on the perjury from that deposition, but in fact, a good argument can be made that it has not run,” he proposed, “because it could not have been discovered because the records were sealed all these years.” The statute of limitations for perjury in Pennsylvania is five years.

Asked whether he has identified any potential statements in the deposition that could support that kind of case, Castor demurred. “I’m not the district attorney anymore." He said he would pursue the case if elected, presuming the deposition occurred in Montgomery County.

While many critics of Cosby want him to face criminal prosecution for the underlying sex crimes allegations, not charges regarding civil testimony, Castor said the consequences for a perjury prosecution of Cosby are quite serious: “You put that old man in prison for three and half to seven years, he’ll die.”

NBC News' Tom Winter contributed.