Constand, 44, left the witness stand after some seven hours of testimony over two days, during which she told the jury that the comedian gave her three blue pills and then penetrated her with his fingers as she lay paralyzed on a couch, unable to tell him to stop.
Constand also testified that she returned to Cosby's home after the alleged assault "with the hopes of asking him what the pills were that he gave her".
In my head, I was trying to get my hands to move, my legs to move, but I was frozen. Vulture adds that Constand repeatedly contacted Cosby after the alleged assault happened in an attempt to find out what he gave her and to confront him about what happened, but Cosby only said at the time that he thought she "had an orgasm".
The only woman to secure a trial against Bill Cosby for sexual assault has taken the stand - breaking her silence of more than 10 years and telling a jury that the once-celebrated entertainer drugged and assaulted her in 2004.
After a series of phone calls, Constand, who was then in her 30s, said the married Cosby began inviting her to dinner at his house and other events.
Constand's testimony on Tuesday casts new light on Cosby's assertion that Constand consented to the sexual activity because, as he said in the 2005 deposition, "She does not look angry".
Constand is one of around 60 women who have accused Cosby of sexually violating them but the prosecution has gone ahead on just Constand's allegations due to the statute of limitations passing for almost every other of those claims.
Cosby has faced allegations of sexual assault from dozens of women, though Constand's accusation is the only one to lead to criminal charges.
The defence has attacked Johnson's credibility over discrepancies in her accounts, including the year it occurred. She testified in Norristown, Pennsylvania's Montgomery County Courthouse Tuesday.
Constand's cross-examination will continue when court resumes Wednesday. And I felt Mr. Cosby's hand groping my breasts under my shirt. She felt "terrible" about it, she said, especially when her mother brought Cosby some Canadian souvenirs.
The accuser also recollected the moments when Cosby tried to physically assault her.
Constand has told jurors how her professional relationship with the Temple University trustee evolved into a friendship. She awoke in bed next to Mr Cosby, her clothes undone, it is claimed.
Ms Constand has been barred from talking about her allegations for almost 12 years, following a successful civil case she brought against the comedian in 2006.
She came out of nowhere, Andrea Constand did, swooping in without notice, all dressed in white, a blizzard in June.
"The room was dark, and there was a nice mood in the room, correct?" she said. Cosby told her the pills would help her relax, take the edge off. He said Ms Johnson made the disclosure while pursuing a claim that she had developed debilitating stress from her secretarial job at the William Morris Agency. "I don't want that", Time magazine reported.