Former DA in Cosby case says technicality could result in criminal charges getting thrown out

The criminal charges against comedian Bill Cosby — alleging he raped a woman after drugging her — could be in jeopardy after a former district attorney revealed he had agreed not to use a key piece of evidence, CNN reports.

The email sent last year by former D.A. Bruce Castor to his successor, Risa Vetri Ferman, says Castor made a verbal agreement with Cosby’s attorneys, with the goal of getting him to testify in a civil sexual assault suit brought against him in 2005.

Castor wrote that the intent was to give alleged victim Andrea Constand a good chance at winning her lawsuit by preventing Cosby from invoking his fifth amendment right.

The deposition given in the lawsuit was a key piece of evidence prosecutors are using in their case against the 78-year-old comedian in Montgomery County.

"I can see no possibility that Cosby's deposition could be used in a state criminal case, because I would have to testify as to what happened, and the deposition would be subject to suppression," Castor wrote in the email obtained by CNN. "I cannot believe any state court judge would allow that deposition into evidence. .... Knowing this, unless you can make out a case without that deposition and without anything the deposition led you to, I think Cosby would have an action against the County and maybe even against you personally."

Constand accuses Cosby of sexually assaulting her in his home in 2004. She is among dozens of women who have come forward to accuse Cosby of sexual assault.

Current D.A. Kevin Steele says the verbal agreement doesn't grant Cosby immunity.

"There is a specific legal method to grant immunity," he told CNN. "That was not done in 2005."

CNN reports Cosby's attorneys have already made a motion to dismiss the case -- a motion Steele says has no merit.

"This agreement, made for the express purpose of inducing Mr. Cosby to testify fully in Ms. Constand's civil litigation against him, led Mr. Cosby to give deposition testimony in 2005 and 2006 without invocation of his Constitutional rights against self-incrimination," Cosby's attorneys wrote, according to CNN. "Now, to fulfill campaign promises, the newly-elected District Attorney has repudiated the agreement and has based these criminal charges on the very testimony Mr. Cosby gave in reliance on the Commonwealth's non-prosecution agreement."