WASHINGTON — Sheriff Jim Pendergraph first noticed the changes in his jail population early in the decade, as illegal immigrants from Mexico and other Latin American countries poured into Charlotte and elsewhere in Mecklenburg County, N.C., to find jobs in the robust North Carolina economy.
In Butler County, Ohio, Sheriff Richard K. Jones became so frustrated with the swelling population of undocumented suspects in his jail a couple of years ago that he symbolically billed the federal government for his incarceration costs and posted a big yellow sign near the jail reading: "Illegal aliens here."
Pendergraph and Jones are part of a growing national debate over how to handle undocumented criminals, a debate that's flared anew with the arrest of an illegal immigrant in the execution-style slayings of three college students in New Jersey.
Criminal aliens, as the federal government classifies them, constitute more than a fourth of the inmates in federal prisons. Those still at large often fall between the cracks of an overburdened and uneven enforcement system, escaping detection and deportation.
More than 300,000 criminal aliens are expected to be placed in state and local jails this year, according to a forecast last year by the Department of Homeland Security’s inspector general. Most might remain in this country after serving their sentences because the federal government lacks the resources to identify, detain and deport them, the audit said.
The suspect in the Newark killings, Jose Carranza, is an illegal immigrant from Peru who was out on bond on assault and child-rape charges. Authorities said they were unaware that Carranza was in the country illegally, largely because local policy prohibits officers from questioning suspects about their immigration status.
Newark is one of dozens of cities with "sanctuary" policies designed to keep local law enforcement officers from racially profiling suspects and intimidating immigrant communities, thus making them reluctant to report crimes and cooperate with authorities.
Newark Mayor Cory Booker said local law enforcement shouldn't be trying to determine "whether people are documented or undocumented immigrants." But New Jersey Attorney General Anne Milgram, responding to the uproar over the murders of the three students and the wounding of a fourth, has ordered state and local officers to ask suspects about their immigration status and, if necessary, to notify federal immigration officials.
The Newark case erupted barely two months after Congress abandoned efforts to overhaul immigration laws, bringing new calls from law-and-order conservatives to further safeguard the border and root out lawbreakers among the nation's 12 million or more undocumented aliens.
Pro-immigrant groups and a number of big-city police officials defend sanctuary policies and argue that often-undermanned police departments should concentrate on enforcing state and local laws rather than federal immigration policy.
The Immigration Policy Center, in a study this year, contends that the perception of "immigrant criminality" is greatly exaggerated, noting that crimes by illegal immigrants are proportionately much less than those committed by native-born white males.
But others, including Pendergraph and Jones, say the accused immigrant in Newark is just one example of what they describe as a deeply flawed approach to dealing with criminal aliens.
"Most of them fall between the cracks," Pendergraph said. "How many in this country are arrested daily for serious crimes, and have been convicted of serious crimes before, and nobody has bothered to check on their immigration status? It’s obscene."
Five years ago, about 2 percent of the inmates in the Mecklenburg County lockup were illegal immigrants. Now 21 percent are, around 450 people accused of offenses ranging from minor driving charges to murder, drug dealing and armed robbery.
"It runs the spectrum," Pendergraph said. "There's more of them and they’re getting bolder."
In Oregon, Alejandro Emetrio Rivera Gamboa, an illegal immigrant from Mexico, was convicted twice last year for drunken driving. But immigration authorities didn’t learn of his undocumented status until after he was charged with murdering a 15-year-old girl.
Juan Felix Salinas, another illegal immigrant, was out on bail from a previous arrest when he was charged in a drunken-driving accident that killed a Houston couple and a 2-year-old boy in August.
Jose C. Rivera, an illegal immigrant from Honduras, returned to Charlotte less than a year after he was deported as a convicted felon and was about to be deported again when police charged him with three rapes.
Immigration and Customs Enforcement, a branch of the Department of Homeland Security, is charged with finding and removing criminal aliens. But ICE officials say they're stretched thin and often hampered by state and local sanctuary policies that limit cooperation.
"Those policies represent a significant problem for ICE," said Deborah Achim, the ICE assistant director for detention and removal operations. "What we hope for is to improve our relationship with these local law-enforcement agencies."
The International Association of the Chiefs of Police, in a recent report, outlined a patchwork of uneven enforcement, saying that some law enforcement agencies welcome a partnership with ICE while others have little or no interest in engaging the federal agency. Others complain that ICE is unable to "respond to their needs" consistently.
The police departments of eight major cities — including Houston, Los Angeles, New York, Seattle and Miami-Dade — said in a joint statement last year that local police can't "even begin to consider dedicating limited local resources to immigration enforcement" until the federal government seals the border.
At the other end of the spectrum are state and local law-enforcement agencies that essentially team up with the federal government to enforce immigration laws under a program known as 287g. The officers undergo federal training and can tap into federal immigration data.
At least a half-dozen states and 26 cities are participating in the program, created by a 1996 immigration law. Pendergraph enlisted Charlotte-Mecklenburg in the program last year to respond to the growing number of undocumented offenders. Of 4,600 foreign-born inmates placed in the jail since May 2006, 2,580 have been put in removal proceedings.
(Fort Worth Star-Telegram researchers Stacy Garcia, Cathy Belcher and Marcia Melton contributed to this article.)