A Columbus man has been sentenced to 15 months in prison for telling Cincinnati firefighters he was a medical student so he could ride with paramedics on ambulance runs. Authorities say 20-year-old John Holliman never treated patients. He was convicted of one count each of practicing medicine without a certificate and disrupting public service and was sentenced yesterday. Assistant Fire Chief Bob Kuhn says Holliman told paramedics he was a medical student from Dayton. Firefighters say they got suspicious when Holliman referred to the fire chief by his first name instead of calling him "chief" or using his full name. Kuhn says ambulance ride-alongs are now limited to paramedic trainees and the media, and officials check out all credentials.