The actor Kevin Spacey is “a sexual bully” who “delights in making others feel powerless and uncomfortable,” a prosecutor instructed a British jury on Friday. Speaking at Southwark Crown Court, the prosecutor, Christine Agnew, outlined her case in opposition to the Academy Award-winning actor, who’s on trial in London dealing with a number of expenses of sexual assault.

Ms. Agnew stated that the actor’s “preferred method” of assault was to “aggressively grab other men in the crotch.” On one event, she stated, Mr. Spacey had gone additional and carried out oral intercourse on a person whereas he was asleep.

The actor “abused the power and influence that his reputation and fame afforded him” to take “who he wanted, when he wanted,” Ms. Agnew stated.

Mr. Spacey has pleaded not guilty to all charges.

The actor, 63, faces 12 charges related to incidents that the prosecution says involved four men and occurred between 2001 and 2013. For much of that period, Mr. Spacey was the artistic director of the Old Vic theater in London.

Ms. Agnew said that the complainants included an aspiring actor and a man whom Mr. Spacey had met at a work event. Under British law, it is illegal for anyone to identify complainants in sexual assault cases or to publish information that may cause them to be identified.

Patrick Gibbs, Mr. Spacey’s legal representative, gave a short statement stressing his client’s innocence. He said the jury would hear some half truths, some “deliberate exaggerations” and “many damned lies.”

He asked the jury to consider the complainants’ motivations, and to think about whether the encounters could have been “reasonably believed to be consensual at the time.”

During Ms. Agnew’s statement, she discussed interviews that Mr. Spacey had given to the British police under caution. During one of those, she said, Mr. Spacey said that it was “entirely possible and indeed likely” that he had made “a clumsy pass” at other men but that he would never have touched someone’s crotch “without an indication of consent.”

Throughout Ms. Agnew’s almost 60-minute opening statement, Mr. Spacey sat in a large transparent box in the middle of the courtroom, wearing a light gray suit, white shirt and gold tie, watching intently. On several occasions, he looked at photographs in an evidence bundle. When Mr. Gibbs spoke, Mr. Spacey nodded along and looked at the jury.

Friday morning’s session ended shortly after Mr. Gibbs’s comments. The prosecution its scheduled to call its first witnesses on Monday.