A 23-year-old Southeast Washington man charged with murdering a transgender person last summer pleaded guilty yesterday in D.C. Superior Court, five days before he was to go on trial.

The case against Derrick A. Lewis -- including several pieces of forensic evidence tying him to the shooting of Aaryn Marshall, 26 -- was outlined in court yesterday before Lewis entered his plea to voluntary manslaughter while armed.

Lewis, originally charged with second-degree murder, took the lesser charge as part of an agreement that avoids trial and may earn him a measure of leniency from Judge Robert I. Richter.

When he is sentenced Nov. 4, Lewis faces a minimum of five years and a maximum of 30 years, though newly enacted guidelines recommend a sentence of seven to 15 years.

The slaying Aug. 21, 2003, in the 200 block of Malcolm X Avenue SE was one of three attacks against transgender people that month, two of which proved fatal. Fear spread among the transgender community that bias was behind the shootings.

Assistant U.S. Attorney Blanche L. Bruce, who prosecuted the Lewis case, said yesterday that the reasons behind Marshall's killing remain unclear. "To this day, we don't know what the motive was," she said.

In the other slaying, prosecutors believe bias was the motive.

Earlier this year, a grand jury indicted Antoine D. Jacobs in the Aug. 16, 2003, killing of Elviz Morales, also known as Elvys Perez, and charged that it was motivated by the sexual orientation of the victim.

Morales, 25, a drag performer who was apparently selling sex, was killed near Allison Street and Arkansas Avenue NW, according to prosecutors. Soon after paying for a sex act, Jacobs learned that Morales was in fact a man, prosecutors said. Angry, Jacobs went looking for Morales and shot him, according to prosecutors.

That case appears headed for trial, with an interim hearing scheduled for next month.

In the Marshall killing, the scope of forensic evidence assembled by investigators sealed the case, Bruce said in court and in court papers filed yesterday as part of the plea.

It started with records of Marshall's cell phone, which Lewis used a few minutes after the shooting, Bruce said. Perhaps thinking he could cover his tracks, he punched in *67, which blocked the cell phone number from showing up on the caller identification of the person he was calling, Bruce said.

But when investigators subpoenaed Marshall's cell phone records, they were able to determine that a call had been made to a woman in Maryland after the shooting, Bruce said.

The woman told investigators that she had allowed Lewis to borrow her car and that when he returned it, blood was spattered around the front area of the car, Bruce said. DNA analysis linked the blood spots to the victim, and carpet fibers pulled from Marshall's clothing were found to be a likely match with the carpet of the car, Bruce said.

The woman told police that her .38 caliber revolver was missing. Investigators concluded, based on the bullets recovered from the victim, that the weapon could have been a .38 caliber.

The physical evidence might not have been discovered so quickly, if at all, were it not for Lewis's fateful decision to make a call, Bruce said. "If he had not used the decedent's cell phone, this would probably be open case," she said.