Bill Cosby
Actor Bill Cosby is escorted back after a lunch break during a hearing for his upcoming sexual assault trial at Montgomery County Courthouse in Norristown, Pennsylvania, April 3, 2017. Reuters

Shawn Brown opened up about her affair with Bill Cosby in an exclusive clip from Investigation Discovery documentary "Bill Cosby: An American Scandal," the release of which coincides with the comedian's sexual assault trial that began Monday.

Brown said she didn’t ask the now 79-year-old actor too much about his marriage to Camille Cosby when they first got involved. Brown and Cosby's relationship had turned intimate soon after they started knowing each other.

"When we were on the dance floor, he asked me if I would have breakfast with him later on after the nightclub closed. I asked him, ‘But aren’t you married?' And he said, 'Yes, but my wife stays home with my children. That’s the arrangement that we have,’” she claimed. "I didn’t question him any further because I didn’t think that was my business.”

Read: What Happens To Comedian Bill Cosby’s Career If He Is Convicted Of Sexual Assault Charges?

"My sex life with Bill was just part of our friendship,” she says. "It just had evolved into a sexual relationship. It was consensual.”

Brown claimed that this was only until in 1973 when the "The Cosby Show" star drugged and sexually assaulted her.

"The night that the tone of the relationship changed for me was the night that I went up to his house in Beverly Hills that he was renting off of Canon Drive, and he had fixed me a drink,” she alleges. "No matter where we went in the house he kept carrying this drink with him, saying, ‘Here, drink this, drink this.’ I kept saying, ‘I don’t want anymore.’”

Over the last two years, more than 50 women have come forward accusing the comedian of sexually assaulting them decades ago. Cosby has denied all claims.

On Monday, Cosby arrived for the first day of his trial for allegedly drugging and assaulting former Temple University employee Andrea Constand at his Pennsylvania home in 2004.

Cosby was joined by his "The Cosby Show" co-stars Keshia Knight Pulliam, who played Rudy Huxtable, and Phylicia Rashad, who played Clair Huxtable, at his court appearance.

“I came to support [Cosby] because this is where you hear the facts. This is where the truth happens,” Pulliam told reporters, according to E! Online. “Ultimately, it’s easy to support someone and to be in their corner when things are great. When things are good. But…true family, friendship, integrity is how people show up and support when things aren’t looking so great, when they aren’t shining.”

The trial's first witness was Kelly Johnson of Atlanta, who worked for one of Cosby's agents at the William Morris Agency. She said in court that Cosby sexually assaulted her after encouraging her to take a drug that incapacitated her at a Bel Air hotel in 1996.

She recalled Cosby giving her a “big white pill” and saying: “Would I ever do anything to hurt you? Trust me, it will just help you relax.”

She told the court: “I was very afraid because I had a secret about the biggest celebrity in the world at that time. ... And it was just me and my word against his. I was afraid.”