Gregory Benson, 27, took the witness stand in D.C. Superior Court for nearly an hour yesterday to deny categorically that he had been involved in the slaying last Christmas season of his next-door neighbor.

Benson said he was inside his home at 1523 A St. NE at the time of the murder, and stayed there until investigating officers had talked to him, as they did to all neighborhood residents who were available.

The defendant was supported in his testimony by his father, Joseph, who said that his son had not left the family home at any time around 9:30 p.m., the hour of the slaying.

Young Benson said he was watching television and talking on the telephone at about the time his neighbor, Frank Flook, 33, was shot fatally in the head next door at 1521 A St. Flook had run to his front door last Dec. 27 to help his wife repel two men who were trying to enter their home.

Marilyn Flook, the victim's wife, testified earlier this week that Benson was one of the two men at the door seconds before her husband was shot.

Young Benson said, "I had nothing to do with what happened next door."

He said his sister, who had been downstairs in the basement, shouted that she heard a gunshot. Moments later, he went to the front window where he saw police, fire trucks and neighbors gathered outside, he said.

Benson said he went outside and learned that his next-door neighbor had been killed. He said detectives had asked everyone in the house to remain inside the house until they could get statements from them.

Benson said he talked with detectives and then left the house.

He first learned that he was a suspect on the night of March 18 when, he said, detectives came to his house to arrest him.

Benson, a 1970 graduate of Eastern High School, said he had seen the Flooks on several occasions prior to the shooting. Marilyn Flook testified that she had never seen Benson before the shooting.

On the night of the shooting, Marilyn Flook had gone to her front door after being awakened by the ringing of the doorbell. She said she looked out the front window and saw a person who resembled her newspaper carrier.

When she unlocked the dead-bolt lock on the door, someone began pushing from the outside, she said. She testified that she became alarmed and called for her husband as she struggled to keep the door closed. As her husband ran to help her, one of the men struck his hand, holding a gun, around the door and fired, killing Flook.

The shooting upset residents of the predominantly black neighborhood, some of whom said they believed the couple had been attacked because they were white. The Flooks were the only white couple living on the block of two-story, brick row houses.