Federal Prosecutors Usually Keep Hands Off : Brutality: Officials say local authorities should have the first chance to file cases involving municipal officers.

Like their counterparts in the district attorney’s office, federal prosecutors based in Los Angeles can bring criminal charges against police officers accused of using excessive force.

But they almost never do.

Over the last 10 years, the Public Corruption Unit of the U.S. attorney’s office in Los Angeles has reviewed scores of allegations that individuals’ civil rights were violated through police brutality. Officials, however, can only recall that three cases were prosecuted.

“We always look to local prosecution before we look to federal prosecution,” said Mike Emmick, who heads the Public Corruption Unit. “They’re local police officers and we want to give the local prosecution arms every opportunity to clean up their own shops.”

The number of police-related cases filed by Los Angeles-based federal prosecutors is consistent with other U.S. attorney’s offices around the country.

Nationally, the U.S. Department of Justice annually reviews about 2,500 alleged criminal violations of civil rights laws involving municipal police officers. Since 1985, on the average, 29 civil rights cases have been filed annually, Justice Department figures show.

“The evidence is next to impossible to get,” said Justice spokeswoman Amy Casner. “You basically have to get one cop to testify against another cop, and that’s just about impossible.”

This “code of silence,” which often deters officers from exposing one another’s illicit activities, also deters prosecutors from pursuing cases if there are no independent witnesses or other strong evidence.

Jurors, faced with the choice of believing a police officer or an accuser who may have a criminal record, are inclined to give the officer the benefit of the doubt, prosecutors say.

“If it’s just a swearing contest between an officer and his alleged victim,” Emmick said, “it’s virtually impossible to win.”

Emmick is prosecuting five Los Angeles County sheriff’s deputies and a Los Angeles police officer who face charges ranging from skimming drug money to beating narcotics suspects. Trial in the case is set to begin July 23.

In addition, a federal grand jury in Los Angeles is currently investigating a 1986 case in which two Los Angeles policemen, Sgt. Alan E. Sorkness and Officer Dana P. Hansen, are alleged to have used excessive force in beating and kicking two Latino teen-agers, one of whom suffered a fractured skull. The youths were suspected of car theft.

The last law enforcement officer prosecuted by the local U.S. attorney’s office for civil rights violations was former California Highway Patrol Officer George M. Gwaltney. He was convicted in 1984 in the rape and murder of a Las Vegas woman after a traffic stop near Barstow. Gwaltney was sentenced to 90 years in federal prison.

In 1983, a former Los Angeles County sheriff’s deputy, Douglas P. Linn, and onetime federal drug agent, George Hoelker, were indicted on charges including extortion, threats of violence, and conspiring to sell cocaine. Linn later received 40 years in prison; Hoelker was sentenced to eight.

Under California law, a police officer convicted of assault under color of authority can be jailed or imprisoned for no more than one year per count. Federal law carries a maximum 10-year term if the victim suffers “bodily injury,” and life imprisonment if the victim dies.