About 30 years ago, the newest District Court judge in Prince William County was in his hometown of Norfolk, his car on a tow truck hook, looking to sweet-talk or pay his way out of an expensive and timely ordeal as a result of parking illegally.

The way that longtime prosecutor and now judge William E. Jarvis tells the story, it’s with some distance and caution — but, he says, there’s little harm now. The statute of limitations has long passed.

Jarvis would know. He’s described as an intellectual and a Renaissance man who spends time working on antique motorcycles, cooking Italian or barbecue and learning new techniques for Irish melodies on the violin.

But most of all, colleagues say, Jarvis’s affability and likability outside the courtroom are trumped by his fairness and ethical compass inside it.

On Friday, the Prince William courthouse played host to Jarvis’s formal investiture. He donned the black robe for the first time and took the oath in front of a packed courtroom, which included fellow church members, prosecutors, defense lawyers, law enforcement members and family members.

Jarvis, 49, came in just before the start of the ceremony and looked at the packed courtroom; many people couldn’t find a seat.

“Wow,” he mouthed.

When he took the podium, he said he wasn’t quite sure how to describe the moment of ascending to one of the top rungs of the legal profession.

“This is one of those times where even the verbose can be speechless,” he told the crowd.

In an interview Thursday, Jarvis reflected on a career that he said he carved from an unlikely road. He grew up relatively poor. His late father, Herbert, could not work after being badly injured in World War II. Jarvis always had a job — landscaping, painting, working construction and the like — to help pay the bills.

And although he was someone with many interests, which didn’t really manifest themselves in academics until he attended Old Dominion University, Jarvis was a low-level trouble and mischief-maker.

As he cautiously related the tale about his run-in with the tow truck company, which towed his car despite his pleas, he didn’t admit guilt. He said instead: “All I can say is, the next day, that tow company may have been missing a number of [metal framed] signs.”

Jarvis, the youngest of five children, was a serious athlete and had a mind that constantly wandered to various pursuits in high school, but “one of them wasn’t academics,” he said.

His stance toward academics changed at Old Dominion, where he finished with two degrees, in philosophy and criminal justice, in four years.

“As soon as it was on me, it was fine,” he said of school. “It was people telling me I had to do it that I had a problem with it.”

His mother, Katherine Jarvis, said she taught her children that if you had little money, the only way to succeed was through education. Still, she worried about her youngest son; his excuses for not doing work were innumerable.

“Even as a little tiny kid, he had very, very powerful reasoning and logic,” Katherine Jarvis, 78, said.

His family would often tell him: “ ‘Willie, you ought to be a lawyer!’ ”

After college, struggling with what to do, William Jarvis said he applied to law school as a back-up plan. If anything, he thought he might be a defense lawyer — prosecution was far from his mind.

But after his second year of law school at George Mason University, an internship he had planned on fell through, and he was looking for something to do. He asked to work for free for the Alexandria commonwealth’s attorney. The office agreed.

“A bell went off,” he said. “I loved every second of it. I knew at that point I wanted to be a prosecutor for the foreseeable future.”

Looking back, Jarvis said, what he loves about the job is that “you have the ability to do right every single day” in seeking justice. He said that he has made mistakes but that he generally doesn’t try to look for punishment. He said he tries to look for solutions.

Those sitting at the opposite table agree. “The biggest word you could put in capital letters [about Jarvis] is ‘ethical,’ ” said defense lawyer Mark Crossland, who attended the investiture ceremony.

Jarvis started in Prince William in 2002, just as Commonwealth’s Attorney Paul B. Ebert (D) and other experienced prosecutors were ramping up on the prosecution of the D.C. sniper case, crimes that had drawn national attention for their randomness and brutality.

With the veterans focused on that case, Jarvis was asked to quickly assume a larger role by taking on the bulk of the other homicides. He was already an experienced prosecutor when he came to the county, having worked under Commonwealth’s Attorney David Grimes in Pittsylvania County, Va., and as a prosecutor in Ocala, Fla., where he largely worked on child sex abuse cases.

Recently, Jarvis oversaw the prosecution of Joshua W. Andrews, who was sentenced to life in prison for killing two people in Dumfries in 2002, and Natalia Wilson, who killed her husband’s ex-wife and son. Wilson also received life in prison.

Jarvis was also involved in helping prosecute a man accused of a triple homicide in Manassas, a case he will have to relinquish.

“I have never woken up in the morning and said I don’t want to come to work,” he said. “I have not slept because of horrible things people have done to each other.”

Aside from losing an experienced hand, Ebert said that Jarvis was seen as a keystone in the office, someone who could always help sort through complex legal issues.

“He’s had a lot of experience, and he’s got a sound sense of judgment,” he said.

As Jarvis takes the bench next week, ruling on the kinds of disparate cases that come before a District Court judge — lawsuits, criminal misdemeanors and traffic violations — the moment is bittersweet. He will no longer have the same kinds of relationships with fellow prosecutors or law enforcement.

But he hopes to be accessible. He said outside interests and his background will help him stay grounded in a job in which decisions and rulings are often final.

Much of his job as a prosecutor, he said, was to separate “the knuckleheads from the truly criminal.” He will have a similar role as a judge but will also have a duty “to call balls and strikes.”

He hopes his life has prepared him. “At the end of the day, you have to exercise your own judgment.”