Call him the ultimate deadbeat dad. According to police in St. Charles, Missouri, one motive drove Brian Stewart to allegedly inject his 11-month-old son with HIV-tainted blood in 1992: Child support’s a bitch. Charged last April with giving his son HIV—in order to avoid paying dues because he didn’t believe he was the father—Stewart supposedly told the child’s mother not to bother asking for money because, he said, the boy would not live very long.

For years, Stewart’s son, now 7, was plagued with illnesses. Doctors tested him for everything from diaper rash to diphtheria. When he was finally diagnosed with AIDS in 1996, they called in the cops. A two-year investigation, which ruled out sexual abuse, pointed at the source of the boy’s affliction: His needle-wielding dad. “All possible ways this kid could obtain the virus, including any contact or medical procedures he’d had, were eliminated,” said county sheriff Douglas Saulters. “With the threats the father made, it was determined he was the suspect.”

In February 1992, Stewart, a phlebotomist at a St. Louis hospital, allegedly filled a syringe with stolen, HIV-infected blood, smuggled it into the room where his son was being treated for minor respiratory problems and stuck him with it.

Stewart, 31, pleaded innocent to first-degree assault charges last April. Prosecuters said the charge will be upgraded to murder if the boy dies. Due to the case’s notoriety, Stewart has special protection in jail.