NORRISTOWN, Pa. — Lawyers for Bill Cosby on Wednesday attacked the credibility of 13 women who said they were sexually assaulted by the entertainer decades ago, arguing that their accounts should not be used as evidence in Mr. Cosby’s coming criminal trial on charges of aggravated indecent assault.

Prosecutors say the attacks show a pattern of behavior consistent with what Andrea Constand, his accuser in the criminal case, says happened to her in Mr. Cosby’s suburban Philadelphia home in 2004. They are asking Judge Steven T. O’Neill of the Court of Common Pleas in Montgomery County to allow them to use the women’s testimony under a Pennsylvania law that permits the use of “prior bad acts” if they show a signature pattern of behavior consistent with the charged offense.

But Mr. Cosby’s lawyers say the women’s accounts have little in common with the incident described by Ms. Constand, who says Mr. Cosby drugged her and digitally penetrated her against her will. Mr. Cosby says the encounter was consensual and he has denied assaulting any of the women.

Brian J. McMonagle, the lead lawyer for Mr. Cosby, dismissed the women’s stories as “a bandaged bandwagon of claims that have been put together in a Pandora’s box. It was actually put in that box by clever, cunning lawyers who had the agenda of bringing down an American icon.”