Nancy Cooper was found strangled in an undeveloped subdivision not far from her home in 2008. Prosecutors say Brad killed her because he was angry she intended to leave him, take their children, and move to be with her parents in Canada.
Cooper is charged with first-degree murder.
On the witness stand Friday, Nancy Cooper's friend and confidant Diana Duncan told jurors about the Cooper's relationship.
She recounted fights, and said Nancy Cooper kept her passport and the passports of her daughters in her car because she was afraid Brad would take them to keep her from leaving the country.
Duncan said Nancy told her Brad managed to get the keys to the car and did take the documents.
Later, Duncan talked about the day Nancy Cooper was reported missing. She told the jury she saw Brad Cooper amongst friends who had gathered at a home in Cary.
"His reactions looked false. They looked acted," said Duncan.
Duncan's testimony came a day after the prosecution and defense finished opening statements.
Each side painted Cooper in very different ways.
Cooper's lawyer Howard Kurtz told jurors that Cary police decided Cooper was guilty from the beginning and ignored evidence that didn't fit that scenario.
Kurtz acknowledged that Brad Cooper had an affair, but also said Nancy was involved in a relationship with another man. He even raised questions about the paternity of her youngest daughter, who was born eight months and 24 days after Kurtz said Nancy and the man had an encounter.
In her opening statement Wednesday, prosecutor Amy Fitzhugh told jurors that Cooper made statements to police that were untrue and refused to cooperate before Nancy Cooper's body was found.
Cooper told police his wife went for a jog on the morning of July 12, 2008, and never returned. A man walking his dog found her body two days later.
The Coopers relocated to Cary from Canada in 2001 when Brad Cooper took a job at Cisco Systems in Morrisville. He studied computer science at the University of Calgary and took graduate business courses at North Carolina State University.
Brad Cooper was arrested three months after the murder of his wife. He has spent every day since then in the Wake County Jail.
Nancy Cooper's parents now have custody of the couple's two children in Canada.