The case against Michael Jacques, 47, had been stalled in the courts for five years, in part over whether the death penalty would be sought, the Burlington Free Press reported.
Jacques replied "guilty" to each of the counts read out by U.S. District Judge William K. Sessions III in connection with the death of Brooke Bennett, who disappeared June 25, 2008.
Her body was found covered with dirt in woods a mile from Jacques' house in Randolph.
Jacques pleaded guilty to four counts of producing child pornography and one count of possessing child pornography.
Under his deal with prosecutors, Jacques will spend the rest of his life in prison and forgo any appeals. In exchange, the government agreed not to seek the death penalty and will not take the case to trial.
Court documents indicate, Jacques plotted the girl's kidnapping for a month, trying to make the abduction look like the work of a fictitious sex ring called "Breckinridge."