Tuesday, defense attorneys pulled out testimony from a man who they claim was sexually involved with Nancy.
"They end up naked on the coach together fooling around and he doesn't remember if they actually had sex and they agreed never to talk about it," Cooper's attorney said.
The defense says the stunning allegations were found in evidence provided by the state.
"There is some information in this motion that the Cary police department did not have," Wake County Assistant District Attorney Howard Cummings said.
Cooper's attorney wants the details surrounding police interviews that he claims will prove infidelity in the Cooper's troubled marriage wasn't one-sided.
"The very first phone call when Mrs. Cooper gets an STD test back is to [name's] number, and she wasn't sexually active with Mr. Cooper for years, indicating that she was sexual active," Cooper's attorney said.
Defense lawyers also claim the new evidence proves other people had a reason to kill Nancy Cooper.
"The morning Nancy Cooper ends up missing, [name] leaves his girlfriend's house and is unaccounted for as far as we can tell anywhere in the discovery," Cooper's attorney said.
Cary investigators in the courtroom shook their heads in disagreement.
"He says he was not in the vicinity of the murder and was with other people," Cummings said.
The defense stopped short of accusing Cary police of not following up on leads.
"She's rekindling the relationship clearly and has an intent to meet in June according to their notes, but there is not a single piece of information as to them contacting him," Cooper's attorney said.
The state kept to its argument, saying the defense had all the information.
The judge says he is going to spend more time reviewing the arguments made in court.
Brad Cooper's trial is set for late October.