COLUMBIA - Electronic monitoring requirements under a new South Carolina law might keep some sex offenders behind bars longer than their sentence demands.

The law requires lifetime electronic monitoring of child molesters once they're released from prison. The satellite technology used to track offenders requires they have a dedicated phone line and a way to recharge their Global Positioning System, said Pete O'Boyle, a spokesman for the state Department of Probation, Parole and Pardon Services.

That means sex offenders who can't find a home won't be released, and those who find themselves homeless after leaving prison must go back, Mr. O'Boyle said.

"We have to know where these people are," he said. "If they can't find a place to live, we can and will bring them back before the parole board."

The department has identified 23 homeless sex offenders now on probation or parole, scattered throughout the state. The law, which took effect July 1, does not apply to them, Mr. O'Boyle said.

But if child molesters convicted before July 1 violate their probation or parole conditions, the department will recommend they strap on a GPS system for life, too. That hasn't happened yet, he said.

Former prisoners ending up homeless is not a new problem. But the new law, which also lengthens prison sentences and allows prosecutors to seek the death penalty against repeat child molesters, puts a twist on the issue, Mr. O'Boyle said.

Some shelters are more strict than others on how they handle sex offenders, who must update authorities on their whereabouts for life.

Wayne Fields, the executive director of Oliver Gospel Mission, said the Columbia nonprofit runs background checks on homeless men who seek to live at the shelter and undergo drug and alcohol recovery programs.

A criminal past wouldn't bar someone from the program, but the mission would put more restrictions on that person, Mr. Fields said. In his five years at the mission, he recalls just one applicant whose name was on the state's sex offender registry.

The Salvation Army shelter in downtown Columbia is more open. Ten registered sex offenders currently list the shelter as their address.

Capt. Ethan Frizzell, the Salvation Army's corps officer for Columbia, questioned the number, because the homeless come and go and sometimes don't change their address. But he'd rather they be at the shelter than on the streets. The shelter takes both men and women, but children aren't allowed.

"If there are 10 here under disciplined programming, at least we know where 10 of them are," Capt. Frizzell said. "If we do nothing for them, that doesn't work either."