If cameras had been present, it would have been a viral moment.

Partway through her closing argument on Tuesday, Kristen Gibbons Feden, a 35-year-old prosecutor, strode across the courtroom and stared down Bill Cosby from a few feet away. Fighting off the defense’s attempts to paint Mr. Cosby’s main accuser as a “con artist,” Ms. Feden told the packed house that the real con artist was “the man sitting right there.”

At another point, Ms. Feden saw what she thought was a smile spreading across Mr. Cosby’s face. “He’s laughing like it’s funny!” she said, a shot that later prompted Mr. Cosby’s team to dispute that he had laughed.

And she lit into Kathleen Bliss, one of Mr. Cosby’s lawyers, who had attacked some of the women who testified against him as promiscuous party girls out for cheap fame and a payday.

“She’s the exact reason why victims, women and men, of sexual assault don’t report these crimes,” Ms. Feden said.