TAMPA - Daniel Brock won high praise for jailing impaired motorists. Mothers Against Drunk Driving honored him. So did his bosses.

But one of Hillsborough County's most aggressive DUI deputies may have wrongly sent dozens of people to jail, the Sheriff's Office acknowledged Thursday.

In one year, Brock arrested 58 people whose blood-alcohol content was below 0.08, the level at which state law presumes a driver is impaired, an internal affairs audit showed.

"I don't prescribe to the theory that somehow you have to be 0.08 to be drunk or impaired, " Brock, 38, told investigators.

In 43 of those 58 cases, motorists demonstrated no visible impairment behind the wheel, according to an internal affairs report made public Thursday. In 41 arrests, Brock also failed to make a case with urine samples, the report states.

He said drivers incorrectly recited the alphabet, used arms for balance and slurred speech - when the video showed correct alphabets, perfect balance and clear speech.