Already given dozens of life sentences for kidnapping and sexually assaulting two boys, Michael Devlin pleaded guilty in federal court Wednesday to making sexually explicit photographs and videotapes with one of the boys, and also taking him across state lines.

Devlin pleaded guilty to six counts in the last of a series of court proceedings this week in which he pleaded guilty to dozens of child kidnapping and sodomy charges for the abduction and abuse of Ben Ownby and Shawn Hornbeck.

He pleaded guilty to coercing a minor to engage in sexually explicit conduct to produce photographs and pornographic video tapes and transporting a child across state lines for illicit purposes. The photographs and videotapes were of Devlin and Shawn Hornbeck, now 16, engaged in sexually explicit conduct.

U.S. District Judge Jean Hamilton ordered a pre-sentencing investigation to be prepared, a standard procedure. She scheduled Devlin's sentencing for 9 a.m. Dec. 21.

Citing Devlin's guilty pleas, state Sen. John Loudon said Wednesday that he will propose legislation making some child kidnappers eligible for the death penalty.

"This guy really illustrated every parents' worst fear -- that their child could be minding their own business and literally disappear and be used in this kind of horrific way," said Loudon, R-Chesterfield.

Loudon's proposal would create the crime of "aggravated child kidnapping," which occurs when a child younger than 18 is kidnapped or confined and then raped or sodomized. It would be punishable by either death or life in prison.

If lawmakers were to pass Loudon's bill next year, it could not apply retroactively to Devlin.

Under current Missouri law, only first-degree murder is eligible for the death sentence.

Several other states already have laws allowing the death penalty in certain child rape cases.

During this week's hearings, Devlin described how he tortured young Shawn Hornbeck, then 11 years old, in 2002. He told of how he tried to kill Shawn, but the boy promised to do anything Devlin wanted if he would let him live.

Devlin also admitted to beginning the same effort with a second boy before the victims were discovered alive in Devlin's apartment early this year.

Devlin received dozens of life sentences after his pleas, assuring he will spend the rest of his life in prison for kidnapping and sexually abusing Shawn and Ben Ownby.

The hearings were part of an elaborate deal his attorneys struck in four jurisdictions where Devlin was charged with more than 80 counts, including sexual assault, kidnapping and attempted murder.

Devlin said through his attorneys that he accepted his punishment because he knew what he did was wrong -- a statement quickly dismissed by prosecutors and the boys' families.

"He pleaded guilty because he does not want the world to know the full extent of what he did," said St. Louis County prosecutor Robert McCulloch.

Prosecutors laid out new evidence showing that Devlin tortured Shawn during his first days in captivity and made the boy promise not to flee in order to stay alive. It was a "devil's bargain" that kept Shawn under Devlin's sway for more than four years, even as the boy had phone and Internet access, said Shawn's stepfather, Craig Akers.

"We know now the details that made him not run away," Akers said after the hearings Tuesday.

Devlin pleaded guilty to six counts in Washington County on Tuesday, accepting the maximum sentence of three life terms in prison plus 60 years for kidnapping, sexually assaulting and attempting to murder Shawn in 2002.

During that hearing, Devlin -- standing just feet away from Shawn's weeping parents -- admitted in graphic detail how he abducted Shawn in 2002 and described the point at which Shawn apparently turned from a kidnap victim into a powerless captive.

After Shawn was abducted at gunpoint while riding his bike in rural Washington County, Devlin took the boy to his apartment in suburban St. Louis, where he repeatedly sexually assaulted Shawn. Days later, Devlin took Shawn back to rural Washington County in his pickup truck, apparently intent on killing the boy.

He said he pulled Shawn from his truck and began to strangle him. Shawn resisted.

"I attempted to kill (Shawn) and he talked me out of it," Devlin said.

Devlin stopped the choking, but then sexually assaulted the boy again. Prosecutors say it was at that point that Shawn told Devlin he would do whatever was asked of him to stay alive.

In St. Louis County, prosecutors said Devlin kept Shawn tied for weeks to a futon or a couch, with duct tape over his mouth. Devlin left the boy alone when he went to work during the days, then returned at night and repeatedly sexually assaulted him.

Prosecutors say Devlin also made a videotape of himself torturing Shawn while the boy screamed for him to stop.

Prosecutors said Devlin began abusing Ben Ownby immediately after abducting him Jan. 8. Devlin abused the boy each day until authorities found Ben and Shawn in Devlin's apartment and rescued them Jan. 12, as Devlin, a pizzeria manager, worked the day shift.

Also Tuesday, Devlin pleaded guilty to 71 counts in St. Louis County Circuit Court -- two counts of kidnapping and 69 counts of forcible sodomy of Ben and Shawn. He was sentenced to 18 consecutive life sentences in St. Louis County.

Washington County Prosecutor John Rupp said he was satisfied with the sentences.

"You heard it from his own mouth. You've heard what kind of a monster he is," Rupp said.

Devlin's attorneys said the evidence against their client made a trial "impossible."

Attorney Michael Kielty referred to a videotape prosecutors described Tuesday.

Kielty said he wouldn't comment on what sentence he expects Devlin to receive in federal court on Wednesday.

The sentences Devlin has received so far mean he will probably die in prison. Devlin is expected to serve his time in the state prison system.

While it is The Associated Press' policy not to identify suspected victims of sexual abuse in most cases, the story of Shawn and Ben has been widely publicized and their names are well known.