A Northeast Washington man who killed a prostitute last year after realizing that the prostitute was not a woman was sentenced yesterday to 10 years in prison.

Derrick A. Lewis, 23, who pleaded guilty in August to voluntary manslaughter while armed in the death of Aaryn Marshall, said only a few words during yesterday's sentencing in D.C. Superior Court.

With several of his relatives sitting among the spectators, Lewis said he did not want to inflict any more pain on the family of Marshall, who was a 26-year-old transgender person from Southeast Washington.

The slaying on Aug. 21, 2003, in the 200 block of Malcolm X Avenue SE was one of three attacks against transgender people in the city that month, two of which were fatal. The attacks raised fears of a wave of bias crimes against transgender people.

Although prosecutors have alleged such bias in the other killing, they did not in the slaying of Marshall. In fact, until Lewis and his attorney addressed the court yesterday, the motive had remained murky.

Lewis's attorney, Anthony Matthews of the D.C. Public Defender Service, depicted the killing as a crime of impulse -- a bad choice but not the action of a bad man. When Lewis realized that Marshall was not a woman, he became angry and the two began fighting in the close confines of Lewis's car, the defense lawyer said.

Matthews said Lewis carried a gun because he worked at a strip club, where he was responsible for escorting performers to their cars and fending off the advances of customers. When Lewis drew the gun on Marshall, Matthews said, he was simply trying to force Marshall out of the car.

D.C. sentencing guidelines, which are not mandatory, called for a prison term of 71/2 to 15 years.

Assistant U.S. Attorney Blanche L. Bruce, who prosecuted the case, urged Judge Robert I. Richter to take into account the effect of the killing on Marshall's family and on a community that last year led big cities in homicides per capita.

"This was a totally unjustified homicide," Bruce said. "Aaryn Marshall should be living right now."

Lewis used Marshall's cell phone immediately after the killing, and records of that call helped lead police to a woman who let Lewis borrow her car that night. Blood spots in the car were linked by DNA testing to the victim, prosecutors said.

When his turn came to speak, Matthews asked the judge to sentence Lewis to the low end of the suggested prison term, stressing that Lewis had not been in trouble before and that by pleading guilty, he had accepted responsibility.

"Mr. Lewis did not intend for anybody to die," Matthews said.

Richter said the crime merited more than the low end of the suggested penalty. He urged Lewis to make use of his time behind bars and to chart a course for the life he will lead after he is released.

In another case stemming from the violence last year, Antoine Jacobs is scheduled to go on trial next month in the slaying of Elviz Morales, a transgender person who was also known as Elvys Morales.