Updated 03/23/11 – 3:55 p.m.

ROLLING MEADOWS, Ill. (CBS/WBBM) — A Cook County judge has found a former Streamwood police officer guilty of aggravated battery and official misconduct for repeatedly hitting an unarmed man with his baton last year.

Former Officer James Mandarino was caught on tape by his dashboard camera as he repeatedly struck Ronald Bell with his baton after a traffic stop on March 28, 2010. In the video, Mandarino is seen striking the man some 15 times.

As CBS 2’s Roseanne Tellez reports, Judge Thomas P. Fecarotta said Wednesday that he watched that video 50 to 60 times and found the beating “unprovoked, unnecessary and unacceptable.”

The judge found Mandarino guilty of aggravated battery and official misconduct, a day after attorneys presented their closing arguments.

“Any rational analysis will show that the conduct of the defendant was wrong, just plain wrong, unprovoked, unnecessary and unacceptable,” Fecarotta said.

Mandarino was already fired by the Streamwood Police Department, but was supported in court by many of his fellow officers.

Still, Mandarino’s claim that the two men he pulled over were agitated and aggressive didn’t hold up in the face of that video and his conviction could land him in prison for up to five years.

He has said the tape doesn’t tell the whole story.

During a six-day bench trial, Mandarino testified that he used force because he feared for his life. He said he was in the middle of a high-risk traffic stop, and that Bell and his passenger ignored his dozens of orders to stay in their car after pulling into a driveway.

Mandarino said the passenger, Nolan Stalbaum, smelled of alcohol and kept shouting expletives at him, saying, “I don’t have to listen to you” and began to walk into the house.

The former officer beat Bell repeatedly with his baton as Bell knelt on the driveway.

Fecarotta said he believed that Bell and Stalbaum were drunk and not telling the whole truth about what they did, but added “if a picture speaks a thousand words, the video speaks a million.”

Bell was treated for head injuries he suffered from the beating.

Defense attorneys argued Bell refused repeated orders to lie on the ground, instead remaining in a kneeling position and resisting arrest.

During the trial, Mandarino testified that he was alone and waiting for backup after pulling the two men over, when Stalbaum went inside the home.

“I was in fear at any moment he could come out and may have a weapon with him,” Mandarino testified. “The red flags are going off … I felt anxiety. At any moment I could be killed or seriously injured.”

Bell wasn’t in the courtroom for the verdict on Wednesday. He was at work, but told relatives he was elated.

Mandarino was allowed to stay free on bond pending his sentencing hearing on April 25.

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