OKLAHOMA CITY -- Oklahoma on Friday became the fifth state to allow the death penalty for certain sex crimes, although legal scholars questioned the constitutionality of the new state law.

Under the measure signed by Gov. Brad Henry, anyone convicted twice for rape, sodomy or lewd molestation involving children under 14 can face the death penalty.

South Carolina's governor signed a similar law on Thursday allowing the death penalty for offenders convicted twice of raping children younger than 11. Louisiana, Florida and Montana also have laws allowing the death penalty for certain sex crimes.

Defense attorneys and death penalty experts said the laws defy recent U.S. Supreme Court decisions that have scaled back the death penalty's application.

Barbara Bergman, president of the Washington-based National Association of Criminal Defense Lawyers, said Supreme Court decisions have made it clear that the death penalty is reserved for someone who has taken another life.

"I'm not saying that raping a child is not a horrible crime, but no one has died," said Bergman, who was part of the defense team that avoided the death penalty for Oklahoma City bombing conspirator Terry Nichols following his 2004 conviction on 161 murder counts.

David Brook, a law professor at Washington and Lee University in Lexington, Va., said the measure might actually put a child rape victim's life at risk.

"The last message you want to give an offender who has the life of a child in his hands is you might as well kill the child because he's already got the death penalty," said Brook, who runs the Virginia Capital Case Clearing House, which assists lawyers in death penalty cases. "This is a very stupid message."

No one convicted of a sex offense has been executed since the U.S. Supreme Court reinstated capital punishment 30 years ago, though one inmate is on death row in Louisiana following his 2003 conviction for raping an 8-year-old girl.

South Carolina's new law is named for 9-year-old Jessica Lunsford, a Florida girl who was kidnapped, raped and suffocated last year by a registered sex offender.

"Jessie's Law is about sending a very clear message that there are some lines you do not cross, and that if those lines are crossed the penalties will be severe," said South Carolina Gov. Mark Sanford.