A Northwest Washington woman and two men have pleaded guilty in- D.C. Superior Court to the armed robbery and second-degree murder last July 21 of Elton Leon Grant, a 30-year-old Washington merchant who was shot to death while acting as a decoy to help police capture his assailants.

In a hearing before Judge Leonard Braman late Monday, India Stroman, 21, of 6000 13th St. NW pleaded quilty to conspiracy and armed robbery. Arthur Swarn, 26, of 6305 Kilmer St., Cheverly, pleaded quilty to second-degree murder while armed, armed robbery, and possession of an unlicensed revolver.

Melvin Stewart, 23, of 1132 Seventh St. NE, pleaded guilty to seecond-degree murder while armed and armed robbery, Assistant U.S. Attorney Timothy J. Reardon said yesterday.

A fourth person, Leonard J. Anderson, 23, of 51 T St. NW, pleaded guilty last November to second-degree murder while armed and armed robbery in connection with the case.

Elton Grant, who owned Grant & Green, a floor service business at 7323 Georgia Ave. NW, was killed last July 21 after he made cash withdrawals from the Riggs National Bank branch at 14th Street and Park Road NW.

Evidence compiled by the government shows that Stroman, who had been employed by Grant as a secretary until a week before he was killed, met several times with Anderson, her boyfriend, and with Stewart and Swarn to plan te robbery of Grant, Reardon said.

Grant learned of the plans to rob him from a mutual friend who had talked with Stroman. Grant went to the police and agreed to serve as a decoy in police efforts to foil the robbery and arrest Stroman and the three men involved, according to Reardon.

On July 21, Grant -- wearing a bullet-proof vest -- went about his weekly routine of withdrawing cash for his payroll from the bank. Police officers who were staked out near the bank were supposed to rush in and arrest the suspects while the robbery was in progress.

Grant came out of the bank with a brown leather pouch and walked to a nearby parking lot, where he was approached by Stewart and Swarn. Anderson was waiting in a getaway car, according to court records. Government evidence shows that the two men snatched the pouch and Swarn pulled a revolver and shot Grant in the neck, just above his protective vest, according to Reardon.

Reardon said that police apparently could not get to Grant in time to save his life, but the robbers were cornered in a parking lot and arrested moments later.

The week before Grant was killed, Stroman, Anderson, Swarn and Stewart made three other unsuccessful attempts to rob Grant, Reardon said.

The first attempt was on the morning of July 14 when Grant was making his weekly cash withdrawal from the bank. Swarn and Stewart were only a few feet away from Grant when Swarn became frightened and called the robbery off, reardon said.

Later that day, the men went to Grant's office to rob him, but decided not to because of the number of customers going in and out of the store, he said. That night, the three men went to Grant's Silver Spring home, but left after hearing the barking of neighborhood dogs.

Judge Braman ahas scheduled the sentencing of Anderson for Feb. 21.

Judge Braman has scheduled the sentence of 30 years to life imprisonment.

Stroman, Stewart and Swarn will be sentenced on March 20. Stroman could receive up to 20 years in prison. Stewart could be sentenced to 31 years to life, and Swarn -- who actually shot Grant -- could be sentenced to 41 years to life in prison, according to Reardon.