Cathy Evelyn Smith pleaded not guilty to a single murder charge and 13 counts of felony drug furnishing in connection with the March 5, 1982, overdose death of comedian John Belushi. Smith, 38, will return to Los Angeles Superior Court on Dec. 23, when Judge Robert R. Devich, who supervises the county's criminal courts, is expected to name the judge who will preside over Smith's trial. The district attorney's office conceded that Smith did not intend to kill Belushi but is prosecuting her under a legal theory that holds that anyone who commits an inherently dangerous felony during which a death occurs can be tried for second-degree murder. In this case, the dangerous felony is the alleged furnishing of drugs. According to testimony presented at Smith's preliminary hearing, she repeatedly injected Belushi, who was in Los Angeles working on a film script, with "speed balls"--mixtures of heroin and cocaine--in the days and hours before he died.