Prosecutors on Friday seemed cognizant of the defense efforts to depict Ms. Constand in an unflattering light when they asked her why she had agreed to cooperate when they brought charges, even after securing a large financial settlement. “For justice,” she replied.
In more than two hours on the stand, led by Kristen Gibbons Feden, a special prosecutor, Ms. Constand described how an older man she respected, and who was a major source of career guidance, had taken advantage of her trust.
She recalled meeting Mr. Cosby, a famous alumnus of Temple University, where she worked, during a basketball game in 2002. She was an administrator for the women’s team, and she said he subsequently called her office and invited her to dinners at his homes in New York and Connecticut, which she attended. On two occasions, when they were alone, she said, she had rebuffed his advances.
Only once did she pause in her testimony, and that was just before she provided a graphic, detailed accounting of what she said happened at the Cosby home near Philadelphia in January 2004. Mr. Cosby gave her three blue pills, she said.
She testified that he said: “‘Put ’em down. They will help you relax.’”
“I began to see double vision,” she continued.
“I was very scared,” she said. “I didn’t know what was happening, why I was feeling that way.”
Her court appearance followed several days of testimony from five other women who said they, too, believed Mr. Cosby had drugged and sexually assaulted them.
As part of Mr. Cosby’s defense, his lawyers have said they will bring forward an academic adviser at Temple, who said she had roomed with Ms. Constand during university basketball trips and that Ms. Constand had once told her before the incident with Mr. Cosby that she could fabricate a claim of sexual assault about a celebrity to get money.
The adviser, Marguerite Jackson, was barred from testifying at the first trial after Ms. Constand told the court she did not know her. But Mr. Cosby’s lawyers are expected to challenge that testimony when they cross-examine Ms. Constand.
Prosecutors seemed interested in taking some of the sting out of that effort on Friday morning when they asked Ms. Constand about the adviser.
“I recognize the name,” she said this time. But asked if she had ever roomed with Ms. Jackson, she said, “No.”
In recent days, the defense has worked to find holes in the other women’s testimony, suggesting that their accounts were not credible and were probably motivated by a desire for money or media attention.
Mr. Cosby, now 80, is not charged with assaulting the other five women who have testified, but prosecutors hoped to show a pattern of predatory behavior that eventually targeted Ms. Constand, now 45. At the first trial, prosecutors were allowed to introduce only one other accuser to bolster Ms. Constand’s account.
Mr. Cosby has denied any inappropriate behavior and said the sex with Ms. Constand was consensual.
After the encounter, Ms. Constand said, she went to his house several weeks later to confront him. Mr. Cosby discussed the night a bit, suggesting he thought she had had an orgasm, but then evaded her questions, Ms. Constand testified.
As Ms. Constand spoke, Mr. Cosby sometimes sat back in his chair at the defense table, listening carefully. At times, he stared at the ceiling as she spoke.
Ms. Constand said she had feared retaliation from Mr. Cosby if she were to speak out, but nearly a year later she told her mother what happened. Together, they spoke to Mr. Cosby, who, she said, admitted to giving her pills, penetrating her with his fingers, and using her hand to masturbate himself.
“After a very short time on the telephone with my mom there, he eventually apologized for doing what he did, but he would not tell us what he gave me,” she said. “He said ‘I don’t know. I have to go check the prescription bottle.’”
Mr. Cosby has said the pills were Benadryl.
Under cross-examination by Thomas A. Mesereau Jr., a lawyer for Mr. Cosby, Ms. Constand was pressed to explain some discrepancies in her account, such as why she told Pennsylvania police that the encounter had occurred in March 2004, not January, as she had told Canadian authorities and has since insisted.
“I was just trying to recall an enormous amount of information,” she said. “I was nervous.”
In one deposition in the civil case, Mr. Mesereau said Ms. Constand had recounted lying on the bed in Mr. Cosby’s room at the hotel of a Connecticut venue where he was performing. In court Friday she said she had not.
“I was mistaken,” Ms. Constand said. “I was just trying to piece it together.”
Mr. Mesereau suggested that Ms. Constand was the engine driving the relationship, that she flirted with him, accepted gifts of perfume and cashmere sweaters from Mr. Cosby, never asked about his wife and had a closer relationship with him than she was admitting, even visiting and calling him after what she had described as an assault.
“You went back to the house with the person who assaulted you,” he asked, “and after that you had your family go to the theater with him?”
Ms. Constand has said she only went to the house to confront him. She has said she accompanied her family to the theater because her parents — whom she still had not told of the encounter — wanted to see Mr. Cosby perform.