Accused of murdering an young man, Craig Patterson testified Wednesday that when he fired his gun he was protecting himself and trying to detain a threatening and intoxicated stranger.

It is the first time since the May 22 slaying of 22-year-old Julian Dawkins that Patterson, a 45-year-old Arlington County sheriff’s deputy, has publicly offered his account of the fatal encounter. Patterson is charged with first-degree murder.

During his trial in Alexandria Circuit Court, Patterson told jurors that he was going for a late-night walk near his home. He said he carried his service weapon concealed under his shirt, as he always did while off-duty.

During his walk, Patterson said, he encountered Dawkins, who “appeared to be under the influence of something” and questioned why Patterson was in the neighborhood. Patterson said he identified himself as an officer, but Dawkins did not believe him.

“He told me I wasn’t supposed to come around anymore,” Patterson testified. “I said ‘Hey, I live here, I’ll be back.’ ”

That’s when, according to Patterson, Dawkins turned toward him with a knife in his hand and said, “I told you, don’t come back.”

Patterson said Dawkins chased him. When he realized Dawkins was no longer behind him, Patterson decided to make an arrest. “I felt that I had a duty to protect the public at that point, to keep him from doing what he did to somebody else,” he testified.

Patterson said he went to his car to get handcuffs; then he went looking for Dawkins.

When the younger man saw him, Patterson said, Dawkins ran.

Patterson said he chased Dawkins into the yard of 160 Lynhaven Dr. while saying, “Stop, police!” In the “very dark” yard, Dawkins swung at him, and he ducked, Patterson testified. “He charged at me again,” Patterson said. “I saw something in his hand. That’s when I drew my weapon and fired. . . . I thought he had the knife in his hand at that point.”

In shock, with shaking hands, he called 911, Patterson testified.

Dawkins, a well-known and liked driver for the PBS “NewsHour,” was pronounced dead at a hospital soon after. He had been celebrating that night with family because his cousin was just drafted by the Washington Mystics basketball team, family members testified Tuesday.

Under cross-examination by Asst. Commonwealth’s Attorney Bryan Porter, Patterson said that he had planned to call 911 once he located Dawkins and only detain him “if necessary,” but that the pace of the incident gave him no chance to make the call. He also acknowledged that he mistakenly believed that he had a right as a law enforcement officer from another jurisdiction to arrest Dawkins.

“I was under that impression,” Patterson, a 17-year veteran of the sheriff’s department, said. “I was wrong.”

The grueling hour of testimony offered Patterson a chance to explain his thinking and his actions the night of the shooting. But it also gave Porter an opportunity to grill the defendant on his judgement. Patterson acknowledged that he had never used his firearm outside of training before, that the Arlington sheriff’s office does not handle street crime, and that outside of six months serving warrants at least a decade ago, he had never arrested anyone.

Patterson was calm throughout his testimony , although he appeared to become briefly choked up while describing his final interaction with Dawkins. He did not learn that the young man was dead, he said, until he was interviewed by a homicide detective at police headquarters later that morning.

After that interview Patterson packed a bag and went to stay at the home of his ex-wife, Najah Patterson, he said. She testified that the next day she sat with him in the house with their pastor and he was “hysterically crying.”

“He’s an extremely peaceful, even-tempered person,” she testified. Their son, 19-year-old Craig Patterson Jr., agreed on the stand that his father is “very cool, calm and collected,” and that “everyone knows my father is a man of integrity.” Several of Patterson’s colleagues and superiors at the Arlington sheriff’s office gave similar testimony, saying the deputy is honest and laidback.

“I’ve never known him not to tell the truth,” said Susie Doyel, director of administration for the sheriff’s office, describing Patterson as “very professional” and “very peaceful.” She added that confusion about jurisdiction for law enforcement was not uncommon.

Testimony in the case has ended. On Tuesday, witnesses for the prosecution testified to hearing the argument between Dawkins and Patterson and seeing Patterson return to the intersection with his gun.

Closing arguments are scheduled for Thursday morning.

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