Michael Jacques' plea allows him to avoid a federal death penalty trial for the 2008 slaying of Brooke Bennett.
When the judge asked him if all of the allegations were true, Jacques replied, "I'm afraid it is, sir."
Jacques, 47, of Randolph, will be sentenced to life in prison without the possibility of parole as part of an agreement with federal prosecutors. They had been planning to seek the death penalty against Jacques, whose trial was scheduled to start after Labor Day.
Prosecutors say Jacques, a convicted sex offender, used a 14-year-old girl he had been sexually abusing since she was 9 to lure Brooke to his home for a pool party by having the girl send Brooke a text message purporting to be from a boy she was interested in. They say Jacques drugged, sexually assaulted and ultimately suffocated Brooke with a plastic bag after she disappeared from a convenience store in Randolph on June 25, 2008.
Prosecutors said Jacques then created an online trail making it look like Brooke was the victim of someone she'd met on the Internet and left her underwear on the side of a dirt road with another male's DNA.
Brooke's body was found buried in a shallow grave off a logging road near Jacques' home after a weeklong search.
After Brooke disappeared, authorities soon uncovered a series of horrifying schemes they say Jacques used for his own sexual gratification.
The other girl told police she thought Brooke was destined for a child sex club the teen believed she had been in herself since she was 9, although prosecutors say it was another ruse created by Jacques.
The teen believed her family would be killed if she didn't engage in sexual acts with Jacques - a threat she believed in part because he went so far as to stab himself in the leg and blame agents of the so-called club, Assistant U.S. Attorney Craig Nolan said.
The lie was so convincing it took much time and effort to persuade the girl the club was a fiction, Nolan said.
During their investigation, authorities said they found four video cassettes in a swamp behind Jacques' house with images of the girl engaged in sexual conduct with Jacques.
Jacques, who was married to the sister of Brooke's mother, initially pleaded not guilty in the fall of 2008. Earlier this month prosecutors announced he had agreed to plead guilty to charges of kidnapping with death resulting, four counts of production of child pornography and one count of possession of child pornography.
"We just think this was a fair and enlightened way to resolve this case," his attorney, David Ruhnke, said afterward.
Brooke's parents and grandmother declined to comment to reporters as they solemnly left the court.
When Brooke's parents, Jim Bennett and Cassandra Adam, first heard about the plea agreement, they said they were disappointed in the outcome.
Jim Bennett, Brooke's father, said he had seen the suspect's name on Vermont's sex-offender registry in the mid-2000s when he had been training as a town constable and tried to discourage the girl from visiting his home. He said he wonders if he had pushed harder to keep his daughter away from Jacques if she might still be alive.
"It's one of those things that's in the back of my mind all the time," Bennett told the Burlington Free Press last week.
Jacques' name was added to the registry after a 1993 conviction for aggravated sexual assault involving a female coworker at a West Rutland business.
Vermont has no state death penalty, but Jacques was to be tried under federal law. His trial would have been the second death penalty trial held before U.S. District Court Judge William K. Sessions III.
In 2005, Donald Fell was found guilty and sentenced to death for abducting a North Clarendon woman as she arrived for work at a Rutland supermarket. She was later killed in New York state. Fell is currently on death row in Terre Haute, Ind.