Original Article Feb 14, 9:50 PM EST Former top prosecutor cited for driving while impaired PHOENIX (AP) -- A former U.S. attorney for Arizona was arrested on suspicion of driving while impaired Tuesday following a minor traffic accident, authorities said. A. Melvin McDonald, now a prominent Phoenix defense attorney, was booked into a Maricopa County jail Tuesday afternoon and spent two hours there before being released on his own recognizance, said county Sheriff's spokesman Lt. Paul Chagolla. Authorities said McDonald's car appeared to rear-end another vehicle while exiting Interstate 10 near downtown Phoenix about 8:30 a.m. No one was injured, but the other driver suspected McDonald may be impaired and called authorities, according to state Department of Public Safety spokesman Rick Knight. Knight said officers at the scene did field sobriety tests and then arrested McDonald, who later submitted to drug tests. "The officers at the scene thought this may be a medication issue," Knight said. "They said he was very cooperative and polite." "I'm a diabetic. I take insulin four times day. I may have had diabetic reaction," McDonald said in a telephone interview. "I do not drink and I am an advocate against drinking and driving." Before becoming U.S. attorney in September 1981, McDonald served as a prosecutor and trial supervisor for the Maricopa County Attorney's Office from 1970-74. He was elected a Maricopa County Superior Court judge in 1974, serving through August 1981. More recently, McDonald led a grand jury investigation into the January 2004 hostage standoff at a state prison in Buckeye. He also conducted an investigation into former Arizona Corporation Commissioner Jim Irvin, who resigned from office over allegations that he influenced a bidding war for a gas company the commission regulated.