The guilty verdicts were a blow for the officers, who did not testify, and their lawyers, who had maintained that their clients committed no wrongdoing and rested their case without calling a single witness or presenting any evidence. A contingent of correction officers has faithfully attended the trial, with dozens of them packing the benches at times.

“Today’s verdict is an absolute travesty and yet another example of how correction officers are treated differently and disrespected for doing the job they are sworn to do: protect New Yorkers,” said Norman Seabrook, the president of the Correction Officers’ Benevolent Association.

Glenn Garber, a lawyer for Mr. Rodriguez, had said in his summation that the prosecution’s case had ignored the dangerous environment the guards worked in, under daily threat from armed gang members. He had argued that “this is simply not the case” to make a point about the “culture of corruption” at Rikers.

The officers, who are scheduled to be sentenced in September, face up to 15 years in prison on the most serious count alone. When convicted of a felony, officers are automatically fired from their jobs under state law, according to correction officials. Even with an acquittal, an officer could still be disciplined by the department, including possibly dismissal.

A 10th officer, Michael Pollard, has also been charged in the beating but will be tried separately because of medical problems.

“We have zero tolerance for any illegal behavior on the part of staff, and the officers found guilty of felonies will be terminated,” Joseph Ponte, the correction commissioner, said. “The vast majority of our officers carry out their duties with care and integrity, and we are taking many steps to ensure that all staff adhere to the highest professionalism.”

Bronx prosecutors had contended that Mr. Perez, a former assistant chief for security, and Mr. Vaughn, a former captain, ordered five members of an elite correction squad to beat Mr. Lightfoot after he caught Mr. Perez’s eye during a search of inmates for weapons. They said that Mr. Perez thought the inmate was a tough guy and told the officers to kick his teeth in.