The sexual assault trial got off to an emotional start on Monday.
A woman testified tearfully that two decades ago, he befriended her, won her trust, plied her with gifts, and then drugged and sexually abused her.
Mr. Cosby is not being prosecuted for his alleged encounter with Ms. Johnson, but her testimony offered a stark rebuttal to his longstanding persona as an amiable comedian and beloved television dad. And her story closely parallels that of Andrea Constand, the woman Mr. Cosby is charged with assaulting.
In 1996, in a bungalow at the Hotel Bel-Air in Los Angeles, Ms. Johnson said, Mr. Cosby talked her into taking a pill that made her feel as if she was “underwater.” She awoke a while later, she said, lying on the bed, partly undressed, with Mr. Cosby behind her; she had lotion on her hand and “he made me touch his penis.”
“My dress was pulled up from the bottom, and it was pulled down from the top,” she said. “My breasts were out. I felt naked.”
Mr. Cosby denies the assault allegations.
The trial in the Montgomery County Courthouse in Norristown, Pa., marks a long-awaited test of the kind of accusations dozens of women have leveled in recent years against Mr. Cosby, now 79, severely undermining the image he built over more than half a century in show business. Rarely has a person so well known faced such a sharp reversal in reputation, or such serious criminal charges —– three counts of aggravated indecent assault, each punishable by up to 10 years in prison.
But those charges are based on what prosecutors say happened to just one woman, Ms. Constand, and Judge Steven T. O’Neill allowed the prosecution to present only one of the other accusers, Ms. Johnson, as a witness who prosecutors contend show that the encounter with Ms. Constand fit a larger pattern. There are no criminal cases pending based on the other allegations, some dating to the 1960’s or 1970’s, often because too much time had passed.
In opening statements, Mr. Cosby’s lawyer attacked Ms. Constand’s credibility.
He said the assault never happened, insisting that his client, while “a flawed husband,” was not an abuser. He described inconsistencies in her account, and conduct that did not suggest she was a victim, like taking her parents to see Mr. Cosby perform near Toronto after the alleged assault.
Mr. McMonagle told the jury that phone records, not previously disclosed publicly, show that Ms. Constand called Mr. Cosby 53 times, some calls lasting half an hour or more, in the months after the encounter in 2004 at his home in Cheltenham, a suburb of Philadelphia. Yet when she went to the police nearly a year later, Mr. McMonagle said, she told them that she had not tried to contact him.
“Her story unravels,” he said.
He also noted that a previous district attorney had decided against charging Mr. Cosby in Ms. Constand’s case. “They saw there was no evidence to bring a prosecution then,” he said. “So why are we here?”
As he spoke, Mr. Cosby sat up and nodded repeatedly.
Discrepancies in the accounts of sexual assault victims are not uncommon, according to experts, but Mr. McMonagle’s statement presages a raw cross-examination when Ms. Constand testifies, expected to be the most dramatic part of the trial. Mr. Cosby has said he will not take the witness stand in his own defense.
But prosecutors told the jury that Mr. Cosby’s own words would convict him.
They cited his admission in a lawsuit deposition that he used quaaludes to have sex with women. Ms. Constand, then a Temple University employee, met Mr. Cosby at a basketball game in 2002 and he became her mentor.
“Trust, betrayal and the inability to consent,” said Assistant District Attorney Kristen M. Feden said. “That is what this case is about.”
Pointing at Mr. Cosby and referring to him repeatedly as “this man,” Ms. Feden told the jurors, drawn from the Pittsburgh area because of pretrial publicity concerns, that they must look past his celebrity to confront the cold calculation of his predatory actions. Then, she graphically described Ms. Constand’s version of the night in question —– an account strikingly similar to Ms. Johnson’s.
He gave Ms. Constand pills and said, “these three friends will help you relax,” and they rendered her immobile, Ms. Feden said. Even if jurors accept the defense’s contention that the pills were Benadryl, she said, it was a dose strong enough, by Mr. Cosby’s own admission, to make himself drowsy.
“This case is about whether Ms. Constand had the ability to consent,” she said. “The answer is no.,” she said.
Mr. Cosby took Ms. Constandt’s hand and used it to masturbate himself, Ms. Feden she said, and he inserted his fingers into Ms. Constand’sher vagina.
The prosecutor dismissed as understandable Ms. Constand’s continued contacts with Mr. Cosby, noting that she had seen him as a mentor who was helping her career, and that he was a powerful alumnus of Temple, her employer. At times, Ms. Feden said, Ms. Constand repressed thoughts about what had happened to her, but she also tried to confront Mr. Cosby, at a restaurant and at his home, about what had happened.
Ms. Feden also cited a phone call between Mr. Cosby and Ms. Constand’s mother, Gianna, who is scheduled to testify, in which she said that he apologized and offered to fly both women to Florida to discuss the episode, and to pay for some of Ms. Constand’s schooling.
The trial, expected to last two weeks, drew a large crowd to the neo-classical courthouse, built in the 1850’s and later expanded. In the courtroom, lined with dark wood paneling and deep red carpet, and lit by eight huge chandeliers, Judge O’Neill apologized to jurors for the cramped conditions.
“You are not to read, or listen or watch anything about the case,” he told them. “You can’t even discuss the case with members of your own family.”
The courtroom gallery was packed with about 130 people, including journalists and spectators, including some who had lined up for seats in the middle of the night. More people were lined up outside, hoping to get in, including two of Mr. Cosby’s accusers, Victoria Valentino and Therese Serignese.
Mr. Cosby’s wife, Camille, did not appear at the courthouse.
Mr. Cosby arrived in a black S.U.V. holding a cane.
He was accompanied into the courtroom by Keshia Knight Pulliam, the actress who played one of his daughters on “The Cosby Show,” and two aides.
“Truth happens here,” Ms. Pulliam said in an interview, while Mr. Cosby, in a dark suit, declined to answer questions shouted by reporters.
Ms. Johnson, the witness, got to know Mr. Cosby while she worked as an assistant to secretary for his agent at the William Morris Agency in Los Angeles. She described how he cultivated her, calling her at home, giving her a bird of paradise plant, even inviting her and her family to see him perform in Las Vegas, and giving her his private number.
Like Ms. Constand, she said she had rebuffed a physical advance —– in Ms. Johnson’s case, she said that she refused a kiss that he said was called for in a scripted scene he asked her to rehearse with him.
Then came the invitation to meet him at the Hotel Bel-Air. Mr. Cosby told her “that I looked like I needed to relax,” she said, and offered her a large white pill. When she first declined to take it, she said that he told her: “Would I do anything to hurt you? Trust me.”
Later, she said, she overheard Mr. Cosby complaining about her to her boss.
Anticipating her testimony, Mr. McMonagle told the jury that when Ms. Johnson complained to human resources and later when she filed a worker’s compensation claim, she never made any accusation that Mr. Cosby had assaulted her. “At no time was she forced to have sex and when she said no, he said O.K.,” Mr. McMonagle said.
Ms. Johnson said that she did not tell anyone at the time what had happened because “I was frightened.”
“I had a secret about the biggest celebrity in the world at that time, and it was just me,” she said.
An earlier version of this article misidentified the hotel where the trial’s first witness testified that Bill Cosby assaulted her. It was the Hotel Bel-Air, not the Beverly Hills Hotel.