- Email outlined details of an apparent agreement between DA and Bill Cosby's lawyers reached in 2005 over a deposition
- In July 2015 a judge unsealed Cosby's deposition given in a civil case, one of his lawyers says he gave it with a guarantee
- The guarantee, Cosby's lawyers say, was the deposition wouldn't be used in a criminal case
- The deposition is key evidence against Cosby, cited by prosecutors as the impetus for reopening the case
(CNN)A former district attorney in Montgomery County, Pennsylvania, claims he agreed more than a decade ago that his office wouldn't use a civil deposition given by Bill Cosby in any criminal matters, an email obtained by CNN shows -- a revelation that could call into question the viability of the criminal case against the comedian.