ST. LOUIS - A former St. Louis sheriff's deputy admitted Wednesday that he bought drugs while in uniform and chauffeured a drug dealer around town.

Jason Stewart, 31, pulled up in his personal vehicle on Oct. 4 to a known drug area which was being watched by a federal and local surveillance team, Assistant U.S. Attorney Hal Goldsmith said in court.

After conducting a transaction, Stewart was pulled over and investigators found 0.17 gram of heroin, a bottle of urine wrapped in a hand warmer concealed in his pants and drug paraphernalia, Goldsmith said. Stewart was in uniform and armed with a .38-caliber revolver at the time.

Stewart later admitted that he was a heroin user and had been for about three years, and that he carried the urine to foil drug tests at work, Goldsmith said. He also admitted that he had driven "at least one heroin dealer" on his rounds through the city in exchange for drugs for his personal use, his plea says.

Stewart pleaded guilty to a charge of being a drug addict or drug user in possession of a firearm.

At his sentencing March 14, Stewart could face 18 to 30 months in federal prison. Prosecutors will argue for a stiffer sentence, as they believe he abused a position of trust. Stewart's public defender disagrees with that claim.