Rene Perez was a drunkard and vagrant, an irritant to the police who had arrested him dozens of times in the neighboring towns of Mount Kisco and Bedford.

One night a year ago, Perez called police from a coin laundry, possibly seeking a lift to a hospital. Instead, prosecutors say, a Mount Kisco police officer drove him to Bedford, hit him hard and left him to die.

The officer, George Bubaris, was scheduled to go to trial Friday on charges that he killed the 42-year-old homeless illegal immigrant.

Prosecutors say Bubaris, 31, drove an intoxicated Perez to an out-of-the-way area and "inflicted blunt force trauma to Perez's abdomen," leaving him severely injured.

Bubaris has pleaded not guilty to charges of second-degree manslaughter, unlawful imprisonment and official misconduct. He could face five to 15 years in prison if convicted of manslaughter.

The case has brought attention to the relationship between police officers and illegal immigrants as law enforcement agencies across the United States consider taking on increased deportation duties and legislation on immigration policy languishes in Congress.

Fellow officers are expected to testify about what Bubaris told them about the night of April 28, 2007, when Perez called 911. Defense attorney Andrew Quinn has not said whether Bubaris will take the stand.

Though the indictment does not say how the trauma was inflicted, a civil lawsuit filed by Perez's brother suggests a nightstick was used.

The civil suit also claims that police in Mount Kisco and Bedford engaged in a policy of "dumping" immigrants over each other's boundaries.

Perez, a Guatemalan, was undocumented, like many immigrants who settle in Mount Kisco, 40 miles north of New York City.

A quarter of the town's population of about 10,000 is Hispanic. Mount Kisco has worked hard to care for such newcomers, with a hiring center that provides classes, a medical center that treats the uninsured and several other programs.

Perez, however, did not take advantage. He had a long history of drunkenness, arrests and 911 calls.

Bubaris, who resigned from the police force in March and is free on US$100,000 bail, has said he was appalled by what happened to Perez and denied allegations of racism.

Fernando Mateo, president of Hispanics Across America, said Monday his organization would be monitoring the trial "to make sure justice is done."

Two other Guatemalans have been killed in Mount Kisco since 2003, both strangled in unsolved cases.

The friction created by large influxes of immigrants in Westchester County has led to recent court cases alleging police bias against immigrant day laborers and voting-rights violations against Hispanics.

Federal authorities have said they will observe the county's prosecution of Bubaris and determine afterward whether a civil rights case is warranted.