“Her bravery in coming forward when she did to report a sexual assault by a powerful, famous man led to the subsequent exposure of him as a serial predator,” he said, “and served as an example to other women, giving them the needed courage to step up and stand up against sexual assault.”

Lynne M. Abraham, a lawyer and former Philadelphia district attorney, said the state’s Supreme Court justices granted few appeals, but if they decided to re-examine the case they would likely review the decision to admit the testimony from so-called “prior bad acts” witnesses since this was such a potentially significant moment in any criminal trial.

“They may think, ‘We may decide the same thing, but we will write another opinion on it so that people realize it is not a blanket rule,’” she said.

Mr. Cosby’s conviction came at a second trial after a first trial ended in 2017 with a hung jury.

On appeal, his lawyers had argued that, when Ms. Constand’s accusations were first investigated in 2005, Bruce L. Castor Jr., the district attorney at the time, had made a binding pledge not to prosecute him in the case. Mr. Cosby said that Mr. Castor’s assurance had induced him to give deposition testimony in a subsequent civil suit filed by Ms. Constand that ultimately was used by the prosecution at trial. In the deposition, Mr. Cosby said he had obtained quaaludes as part of his pursuit of having sex with women.

Though Mr. Castor testified at a hearing to having made such a promise, the appellate panel found it was only a court, and not Mr. Castor, that had the power to grant such immunity. “Such promises exist only as exercises of prosecutorial discretion and may be revoked at any time,” the appellate panel said.

The panel also rejected the argument that Mr. Cosby’s trial had been unfair because Judge O’Neill failed to remove a juror the defense said was biased. Mr. Cosby’s lawyers had asked for the removal, citing the account of another prospective juror who had said she overheard the juror saying Mr. Cosby was guilty.