Mwenda Murithi, the Kenyan-born leader of a notorious Chicago street gang, was arrested 26 times after his student visa was revoked in 2003. Charged with at least four felonies, he served 30 days in the Cook County Jail for a 2007 drug violation. By law, he could have been deported immediately.

Relatives grieve for a teen girl in Chicago after a killing some say could have been avoided had a gang leader's immigration status been reported to federal officials. (Terrence Antonio, Chicago Tribune / June 25, 2007)

But Chicago officials did not report him to immigration authorities because city and county ordinances prohibit them from doing so.

Not long after he got out of jail, Murithi ordered a gang hit that resulted in the death of 13-year-old Schanna Gayden, struck by a stray bullet as she frolicked at a playground.

Murithi, now serving 55 years, is just the sort of person U.S. immigration officials say they want to target under a program known as Secure Communities, which seeks to match the fingerprints of everyone booked into jail against immigration databases.

But the program, launched by the Bush administration and continued under President Obama, has become entangled in the suspicions and recriminations that characterize the debate over immigration policy.

Critics of the program say that turning illegal immigrants over to federal authorities would undermine the efforts of local law enforcement to win cooperation from immigrant communities. And they worry about providing immigration authorities with the fingerprints of those arrested on petty charges.

"I'll be reporting minor offenders, misdemeanants, people who are arrested on a traffic fine that they fail to pay," San Francisco Sheriff Michael Hennessey said. "I think that this throws too broad of a net out over the residents of my county."

David Venturella, who runs the program for the U.S. Immigration and Customs Enforcement Agency, or ICE, said minor violators are not a priority unless they also have more serious criminal histories.

"Our focus is on criminal aliens," he said.

Many major city police agencies forbid officers from inquiring into the immigration status of witnesses and suspects, a policy adopted by local officials to shield illegal immigrants from federal authorities. But the Secure Communities program has divided those cities and the politicians within them.

Houston and Los Angeles are participating in the fingerprint sharing program despite such rules, and San Francisco Mayor Gavin Newsom opposes the efforts of the sheriff and some county supervisors to keep his city out of it.

The federal program was designed to assuage such cities, Venturella said, because it doesn't require their active cooperation. The fingerprints are shared automatically, and ICE officers arrest those they intend to deport.

This arrangement stands in contrast to a more active federal-local effort known as the 287(g) program, under which ICE signs agreements that allow local police to arrest and detain people under immigration laws. Few big cities participate in that program.

Still, out of political sensitivity, ICE currently is not matching fingerprints from counties, such as Cook County, that object to the Secure Communities program, he said.

Secure Communities is operating in 193 counties, including Los Angeles County, and ICE has checked 2.2 million sets of fingerprints submitted by local law enforcement agencies, spokeswoman Randi Greenberg said. Through April 30, there were 216,000 hits against a database of people who previously had been fingerprinted by ICE, she said.

Of that number, 24,000 had been charged with or convicted of what ICE classifies as the most serious offenses, including rape, murder and kidnapping. The remainder involved lesser offenses, ranging from bribery and fraud to petty violations, such as gambling.

ICE deported 6,100 of those charged with or convicted of the most serious offenses, and 14,300 who were charged with or convicted of lesser offenses, she said. The goal is to expand the program nationwide by the end of 2012.

Despite Venturella's assertion that ICE won't focus on people charged with lesser offenses, immigration rights activists aren't so sure.

"We think it's an ill-conceived, ill-functioning program," said Joan Friedland, a senior attorney with the National Immigration Law Center. "Regardless of how or why a person got into police custody, whether it was based on racial profiling, whether it was a minor offense, whether the person is found not guilty, they are subject to deportation."

Friedland said she would be more comfortable with referrals based on convictions, not arrests.

In Cook County, authorities can do neither. While the policies in Los Angeles and other cities allow police to notify immigration authorities about felons they suspect are illegal immigrants, Cook County forbids that, said Steve Patterson, a spokesman for the Sheriff's Office.

Asked why, Chicago Alderman Roberto Maldonado argued that the law does allow the reporting of felons to immigration authorities. "We're not protecting criminals," he said.

The text of the law, however, contains no such provision.

Asked about the case of the Kenyan gang leader, Maldonado noted that ICE, the immigration enforcement agency, routinely peruses county arrest reports. "If ICE didn't have their eyes open, that is not our fault," he said.

In Los Angeles, a case in 2008 reenergized a long-standing debate about the city's policy toward police questioning of immigrants.

Jamiel Shaw II, a 17-year-old football star who had been recruited by Stanford and Rutgers universities, was gunned down in March 2008, allegedly by gang member Pedro Espinoza. Espinoza, a 19-year-old illegal immigrant, had been released from the Los Angeles County jail a day before the shooting after serving time on a gun charge.

Although Espinoza had been in the custody of the sheriff, not the Los Angeles Police Department, activists unsuccessfully sought to use the case to overturn Special Order 40, the LAPD rule that limits the circumstances in which officers may inquire into a person's immigration status. An effort to repeal the policy by referendum failed last year when backers couldn't muster enough signatures to put the measure on the ballot.

Unlike in Chicago, nothing prohibits Los Angeles police officers from referring people they arrest to immigration authorities, said Jorge Villegas, commander of the LAPD operations office.

If police arrest a gang member who has already been deported, for example, officers notify ICE, he said.