Jonathan has scars from his former life. Jagged scars on his neck and the back of his head. He has a history of drug abuse and assault. Some of the punches he threw landed on police officers.

But today his scars are partly covered by a bright pink shirt and black apron. He leans across a gleaming counter to hand over a chicken wrap and fries. “Sea salt or chili salt?” he asks a customer, with an affable grin.

Jonathan, 28, works at Street and Arrow, a cafe in a 31-foot Airstream trailer that offers second chances along with trendy street food. The truck is run, at an arm’s length, by the Scottish police. It’s part of an approach to tackling violence that authorities say has had a notable impact on crime in a city with a rough reputation, and it’s attracting attention in London and beyond.

In 2005, the World Health Organization dubbed Glasgow the “murder capital of Europe.” There had been 83 homicides the previous year in the Glasgow region, where gangs were known for their booze-and-blades culture.

Exasperated police in Glasgow decided to rethink strategy. They set up a violence reduction unit (VRU) guided by the philosophy that violence is like a public health issue: Violent behavior spreads from person to person. To contain it, you need to think in terms of transmission and risk, symptoms and causes.

“You cannot arrest your way out of this problem,” said Niven Rennie, director of the now-national Scottish VRU, a unit funded by the government with a budget of $1.6 million this year.

Scottish police plucked ideas from the Cure Violence project in Chicago, Boston’s Operation Ceasefire and Homeboy Industries in Los Angeles, among other initiatives. They formed partnerships with local teachers, doctors and social workers.

They didn’t abandon traditional policing. Shortly after launching the VRU, police ratcheted up stop-and-search and successfully campaigned for legislation that increased the maximum sentences for carrying a knife. But increasingly, they emphasized the interruption and prevention of violent behavior. They are intervening in hospitals, working with partners in schools and helping former offenders get back to work.

Meanwhile, over the past decade, Glasgow has seen a 60 percent drop in homicides, and violent crime in Scotland has fallen to historic lows.

The notion that the public health approach may have contributed to the decline has brought officers from as far afield as Canada and New Zealand to Glasgow to learn more.

And in London, where knife crime has risen by 50 percent in the past three years, Mayor Sadiq Khan recently announced the creation of a violence reduction unit modeled on Scotland’s. “We have listened and researched the public health approaches in cities like Glasgow, where their own long-term approach over more than a decade has delivered large reductions in violence,” the mayor said in a statement.

Researchers urge caution in assessing the impact of Scotland’s program. They stress the difficulty of pinpointing and disentangling the variables that influence crime rates.

“There are a lot of factors at play,” said Susan McVie, a professor of criminology at the University of Edinburgh.

Scottish police have been “bold, they’ve been progressive in a way that has not happened in the city of Glasgow before,” said Alistair Fraser, a criminology lecturer at the University of Glasgow and author of a book on gang identity. Fraser said the VRU has been successful at changing the narrative about crime, but he was hesitant about more concrete results. “There is a general sense it’s a good thing,” he said, “but little in the way of hard proof.”

The picture is complicated by statistics showing that crime also has decreased in areas of Scotland where the VRU is not active. Other possible explanations for the decline include anti-knife campaigns in Scottish schools and a trend of young people spending more time at home and less lingering on the streets.

Some international comparisons have also shown Scotland to score relatively high on assault rates, although Scottish officials dismiss the comparisons because of different ways of counting and recording crime.

And yet there is consensus that Glasgow’s gang culture is not what it once was.

Growing up in Glasgow, there were places “you absolutely didn’t venture,” Humza Yousaf, Scotland’s justice secretary, said as he sipped tea at the recent opening of the city’s second Street and Arrow cafe, staffed by former gang members and people deemed at risk of offending. Now, Yousaf said, “there’s not a place in Glasgow that I wouldn’t go to.”

And individuals involved with Scotland’s anti-violence efforts say they can see the difference it is making.

Eddie Gorman, 53, spent more than 20 years in prison before joining the VRU. He now works as one of the program’s “navigators,” patrolling emergency wards at the Glasgow Royal Infirmary on Fridays, Saturdays and Sundays — peak days for violence — in hopes of finding people at a “reachable moment.”

“We wear bright pink T-shirts — it’s very nonthreatening,” he said. “Sometimes, when I contact them again after 24 hours, they don’t remember me or my name, but they remember the pink T-shirt.”

Soft-spoken but armed with stories from his own chaotic past, Gorman points people in the direction of help, whether that’s counseling, an alcohol recovery program or housing.

Callum, 27, remembers when he first met a pink-shirted navigator. Early last year, he was rushed to the hospital after being stabbed nine times. It was his 17th visit to emergency room in just over a year. His back is a canvass of scars. (Like others interviewed for this article, he spoke to The Washington Post on the condition that only his first name would be used, so that future employers won’t immediately associate him with his past.)

Callum said that when he drank he became violent, but he didn’t know how to stop the cycle. After getting help with his drinking, he was offered a 12-month job at the Street and Arrow food truck and 18 months of mentorship. Today, he’s employed as a mentor at the second Street and Arrow cafe.

Christine Goodall, an oral surgeon in Glasgow, works in partnership with the Scottish police. A decade ago, she said, hospital staff were inundated with patients pouring in with “broken jaws, broken cheekbones, slashes across the face.”

Upset by what she was seeing on the operating table, Goodall co-founded Medics Against Violence, a network of about 250 health-care professionals — doctors, nurses, dentists, paramedics — who fan out into schools around Scotland and share stories about the consequences of knife crime, including their own firsthand experiences of patching people back together.

Iain Murray, a police inspector who oversees the social enterprise arm of the initiative, including the cafes, said what they are doing is breaking the generational cycle — that if young men and women turn around their lives, then their children are less likely to follow them down a path of violence.

He said that about 150 people have been through the program’s various employment schemes and estimates that about 85 percent have gone on to find other jobs.

Back at the food truck, Jonathan is busy preparing meals for the lunchtime crowd, which included a former offender who used to work at the food truck and now is employed as a supervisor at a nearby shop.

Despite his history of assaulting police officers, Jonathan now counts Murray as a friend. He said he’s working on his issues with authority and values the “feelings check-in” sessions with his mentor at work — a big deal for a Glaswegian like him who grew up thinking that showing vulnerability was a form of weakness.

“It’s like no other work environment,” Jonathan said, shaking chili salt onto a plate of fries.