Jurors returned their verdict against Brian Stewart, 32, of Columbia, Ill., after deliberating for about eight hours. They recommended life in prison, and sentencing was set for Jan. 8.
CBS News Legal Correspondent Kristin Jeannette-Meyers reports that the boy's mother, identified only as Jennifer to protect the boy's identity, wept briefly after the verdict was read. Her son has full-blown AIDS.
"My son has been robbed of a normal childhood and given an unjust sentence of his own," she said.
Prosecutors used circumstantial evidence to convince the jury that Stewart, who worked as a hospital technician at the time, stole HIV-infected blood from his workplace and injected it into the boy during a hospital visit in 1992. Prosecutor Ross Buehler called the injection a "death sentence" for the child.
Stewart "had the knowledge and training to commit this offense," Buehler said during closing arguments. "And more importantly, had the motive."
The circumstantial case was based in large part on incriminating remarks made by Stewart, who told his ex-wife "you don't need to look me up for child support anyway because your son is not going to live that long."
Prosecutors claimed Stewart injected the boy to avoid child support payments.
"Why wouldn't he do what everybody else does that doesn't want to pay child support; you just don't pay it," said defense attorney Joseph Murphy.
Murphy denied the allegations, saying the prosecution presented no actual proof that Stewart injected his son.
"A tragedy is not a crime and theories are not facts," Murphy said. "Mom made an allegation and everyone ran with it."
The defense contends the boy could have contracted HIV in a number of other ways.
The child was hospitalized frequently and lived with three admitted drug users for a three-week period. All three tested HIV-negative.
Buehler claimed the alternative explanations presented by the defense were "red herrings" intended to cloud the facts in the case.
Stewart is expected to appeal the conviction.