Alameda County Sheriff Greg Ahern has defied pressure from activists to stop participating in Secure Communities, a federal program that has led to the deportation of nearly 2,000 county residents since 2008, but now criticism is coming from county leaders.

On Tuesday, Supervisor Richard Valle will introduce a resolution at the weekly board meeting encouraging the sheriff to pull out of Secure Communities, a voluntary program in which local law enforcement officials forward fingerprints of anyone they arrest to federal authorities. The prints are then compared against a database to check criminal histories and immigration status.

In his resolution, Valle says the program breaks the trust that local law enforcement has with the community, costs the county money and leads to unequal treatment of residents, Latinos in particular. He said residents of his diverse Union City neighborhood of Decoto are increasingly afraid of police because they fear cooperation will lead to deportation as stories of families torn apart by Secure Communities continue to surface.

This month, Valle was asked to intervene on behalf of a 22-year-old woman, Jatniel Perez, who was held at Santa Rita Jail in Dublin for four days after DUI charges against her were dropped because of a lack of evidence. After five days, immigration authorities drove her, shackled, to a deportation center in San Francisco. They released her the same day because she met the Deferred Action for Childhood Arrivals policy criteria, allowing her to avoid immediate deportation. She was 7 years old when she arrived with her family from Mexico.

"To experience being treated like an alien is really sad," she said in an interview.

Ultimately, Valle would like to see Ahern withdraw from the program, but supervisors have limited authority over the sheriff, an elected official.

"I want him to reconsider," Valle said. "There are families being separated, and that doesn't have to happen."

Ahern argues that he is following federal policies, even as nearby cities and counties, including San Jose and San Francisco, have stopped cooperating with the program.

"It's not that I am supportive of this program," Ahern said. "We allow ICE (Immigration and Customs Enforcement) to do its job."

Under Secure Communities, if someone arrested is undocumented or deportable, ICE agents may ask police departments and sheriff's offices to hold that person for as long as 48 hours after their scheduled release, excluding weekends and holidays, to give ICE time to take custody.

The federal government reimburses for holds lasting longer than four days, which in the 2012-13 fiscal year netted the Alameda County Sheriff's Office $800,000.

The intent of the program was originally to target the most serious criminals.

But by the end of October 2012, a quarter of the million people targeted nationwide by Secure Communities had never been convicted of any offense, and the vast majority were charged with nonviolent lower-level offenses, according to UC Berkeley Law School's Warren Institute, which analyzed data reported by ICE.

In Alameda County, 76 percent of the 1,947 residents deported under the program between late 2008 and January had no criminal conviction or had convictions involving only minor offenses, ICE data showed.

The 48-hour holds are one of the most controversial elements of the program because people are being detained longer than required, said Cinthya Muñoz, a Just Cause organizer.

She cited the Warren Institute analysis, which found individuals with an ICE hold spend an average of seven more days in Alameda County custody than people not being detained on behalf of immigration authorities.

Working with Alameda County United in Defense of Immigrant Rights, Muñoz helped document dozens of stories of people held in limbo under the program in the county, where one in 16 residents is an immigrant and more than half the children have foreign-born parents.

"The stories will continue until he stops," Muñoz said of Ahern.

Concern over the effect on residents' willingness to cooperate with police drove Oakland police Chief Howard Jordan to support a reform bill, the Trust Act, now in the California Assembly.

Secure Communities has "undermined community policing strategies, harmed public safety and caused significant pain for immigrant victims of crime," Jordan wrote in a 2012 letter to Assemblyman Tom Ammiano.

The sheriff, though, has been slow to budge. He denied that the Sheriff's Office has been keeping people in custody longer than necessary.

"Our own concern is public safety," Ahern said. "Our intention is not to divide families."

Ahern said the California State Sheriffs' Association met last week with ICE officials to review deportations made under the program. Federal authorities in December said they would shift focus back to the most serious criminals, as opposed to going after immigrants convicted of minor crimes to fulfill quotas.

ICE recognized that the system, which has ensnared an estimated 3,600 U.S. citizens since 2008, is not working the way it was supposed to, Ahern said.

As for Valle's resolution, Ahern said it "has no bearing on how I'm going to manage my jail." The Board of Supervisors has no authority to make him operate the jails any differently, he added.

"Their resolution is an opinion, and I don't even know if it will pass," the sheriff said.