Mario D. Johnson, 31, pleaded guilty Tuesday to possession of a controlled substance. He was given credit on his sentence for 116 days already served. URBANA — An Urbana man who admitted he possessed heroin almost two years ago has been sentenced to six years in prison. Mario D. Johnson, 31, who listed an address in the 0-100 block of Michelle Lane, pleaded guilty Tuesday before Judge Tom Difanis to possession of a controlled substance.