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Ronald Zak, Associated Press
U.S. citizen Mike Brennan, 34, from Jacksonville, Fla., leaves a court room after the pronouncement of verdict at Vienna's main court, Austria, on Tuesday, Jan. 11, 2011. An undercover police officer has pleaded not guilty to assaulting the American teacher after mistaking him for an African drug dealer at a subway station in the Austrian capital. The police officer was sentenced to a fine of euro 2,800.

VIENNA — A judge on Tuesday convicted an undercover Austrian police officer of attacking an American teacher after mistaking him for an African drug dealer and ordered him to pay a €2,800 ($3,620) fine.

Mike Brennan, a former football player from Jacksonville, Florida, suffered injuries to his back, head, neck, hand and wrist during the Feb. 11, 2009, incident in a subway station in Vienna, the Austrian capital. The officer, who pleaded not guilty, had faced up to three years in prison.

The Vienna police department has said the officer who was charged — and another who wasn't — mistook Brennan for a drug dealer of "almost identical" appearance and acknowledged they used force and injured him.

Brennan, however, claims the accused officer didn't identify himself before knocking him down on the platform and punching him. The officer, who cannot be named under Austrian law, disputed he hit Brennan.

Judge Patrick Aulebauer found that the attack did not amount to battery but that the officer behaved negligently.

"To a certain extent it's understandable that it came to this mix-up and that you thought Mr. Brennan was the one you're supposed to arrest," Aulebauer told the officer. "But that doesn't mean this mix-up could not have been avoided."

Brennan said he was "not happy" with the sentence and that he would talk to his lawyer, Wilfried Embacher, about possibly suing for damages.

"I still have to deal with the physical and mental pain and that's nothing compared to what his sentence is, it doesn't equal that at all," Brennan told The Associated Press.

During a previous trial session in October, Brennan said it took the officer a long time to flash his badge and that he did so only after his girlfriend spoke to him. The officer, however, countered that his badge was always visible and that he shouted "Police! Police!" before touching Brennan.

The officer said he would use a three-day window to decide whether to appeal the ruling.