Dugan pleaded guilty to Nicarico's death in July and seemed unphased each time he sat in the courtroom, until around 2:15 Wednesday afternoon, when he walked in appearing stressed and stretching his neck and shoulders.
DuPage County State's Attorney Joe Birkett said Nicarico's family "finally has true answers and a realistic step towards closure."
"Brian Dugan is going to Death Row where his fantasies of raping little girls will now turn into a nightmare," he said.
The Nicarico family praised the decision and said it brought some relief.
"We are shedding tears, not of sadness, but of joy. But not really, very very joyful because the death sentence is never really a joyful thing. But Brian Dugan is somebody that deserves it," said Jeanine's mother, Patty. "At least we have the satisfaction of knowing Brian Dugan is on Death Row, a place he did not want to be."
The jury announced they had come to a verdict Tuesday night, then withdrew that announcement and said they would need more time to deliberate.
Earlier Wednesday, jurors sent a note to the judge asking to see a piece of evidence from a 1986 search warrant. Jurors eventually asked to see numerous pieces of evidence from the case, including transcripts of former Illinois State Police Cmdr. Edward Cisowski, who led a 1985 investigation into Dugan.
In the end, jurors decided there was enough reason to sentence Dugan to death for killing the little girl.
The circumstances of the crime may have helped. When Nicarico's body was discovered back in 1983 it was clear that she struggled. Her fingernails left scratches on the wall of her parent's Naperville home. Her raped and beaten body was found two days later in a nearby nature preserve, her head wrapped in a towel bound with tape, which had served as a blindfold.
The sentence will put to rest a decades old murder investigation in which three men were tried for the crime.
One of two men who faced the death penalty, Rolando Cruz, said he feels no sympathy for Dugan.
"I got locked up when I was 20 years old," Cruz said. "He's a disgusting animal. He asked for it when he raped and killed those girls, he asked and begged for it."
Dugan admitted to the kidnapping, rape and murder of Nicarico under hypnosis 24 years ago. It was that, along with DNA evidence, which helped exonerate Cruz and Alejandro Hernandez.
"He knew the clothes she was wearing. He knew amazingly how the blindfold was constructed, " said Rob Warden of the Center for Wrongful Convictions. "We know that DNA implicated Brian Dugan, linked the crime to Brian Dugan -- and Brian Dugan alone."
Former Gov. George Ryan cited the case as one of several that led to his decision to stop all Illinois executions in 2000. The death-penalty moratorium remains in place, though death sentences may still be issued.