Prosecutors are using affairs that began on the extra marital site as evidence of a motive.
Chicago businessman Allan Kustok is accused of shooting his wife in the face at their suburban home in September 2010.
Kustok told a detective that he awoke in bed to a gunshot and found his wife dead by his side, with a .357-caliber revolver clutched to her chest.
During the trial, testimony was heard from two women who said that Allan Kustok had pursued them on the site.
Prosecutors are using the affairs to show a motive, painting Kustok as a philanderer who killed his wife to escape an unhappy marriage.
One woman, stand-up comedian and private eye, Toni Kregelka, testified that she had one night stand with him in a motel after they met on Ashley Madison.
She told prosecutor Lorna Amado-Chevlin: “The site is basically set up for married couples who are looking to have a discreet affair.”
After bringing his wife’s body wrapped in their bed sheets to the hospital, he received texts from another woman he met on the site as police questioned him.
The woman, Kathleen Rettke, was interviewed by police after they took Kustok’s phone, and told investigators that she was texting to arrange a meeting that day.
Noel Biderman, CEO of Ashley Madison, spoke to the Chicago Sun Times and said that this case “was a first”.
Biderman said his company has not been contacted by any parties to the case.
He told the newspaper: “We’re just watching on the sideline.
“From our perspective, we’re not confirming or denying he was using our service.”