Bill Cosby's lawyers accuse prosecutors of trying to use the "tainted, unreliable memories of women, now in their senior years" to build their sexual assault case against him and will seek competency hearings on any accusers allowed to testify.

On the eve of a key pretrial hearing Tuesday, they said the women's memories have been marred by time, media coverage of the case and their friendship with one another. After a memory expert reviewed the women's statements for the defense, the lawyers dismiss the other accounts as "stories of that night spent partying with a famous celebrity."

The two sides will face off in court to determine what evidence can be used at the entertainer's scheduled felony trial in June.

Cosby, now 79 and blind, is charged with drugging and molesting a former Temple University employee in 2004. He has pleaded not guilty and argues that he can't defend himself against vague accusations that stretch back to the 1960s.

Prosecutors hope to have 13 of about 60 known accusers testify to show a pattern of "prior bad acts." Courts can allow the testimony if it shows a very specific "signature" crime pattern.

However, the defense said the accounts range from rape to other sex acts to fondling. And they said some of the women took drugs or alcohol knowingly, while others say they did not.

Prosecutors argue that the drinks, even if taken knowingly, were also laced with drugs that knocked the women out and left them unable to give consent.

Some of the accusers don't even know what year they met Cosby, defense lawyers Brian McMonagle and Angela Agrusa wrote in their filing Monday. Cosby's memory is also fading, they said, to the point he could not answer 90 questions in a civil deposition last year.

At least four of the women "did not realize that they were victims until they heard the accusations of other women in the media," according to Dr. Elizabeth Loftus, the defense psychologist who studies human memory. Her preliminary findings were excerpted in the brief.

Prosecutors in suburban Philadelphia say Cosby routinely used his fame and power to befriend impressionable young women, knocked them out with drugs or alcohol and then sexually assaulted them.

The testimony of the 13 others, should Montgomery County Judge Steven T. O'Neill allow some or all of it, could bolster a case that turns on the question of consent. Cosby, in a decade-old deposition, acknowledged some of the encounters but said they were consensual.