It’s been something of a mystery to criminologists: across North America, homicide rates have been in steep decline for 20 years.

Last month, Statistics Canada reported a homicide rate of 1.56 per 100,000 for the year 2012, the lowest figure since 1966. A Canadian today is only half as likely to be a victim of homicide as in 1975.

The phenomenon is not limited to Canada. The U.S. is also setting records.

Chicago just reported its lowest number of homicides since 1965. New York City had a mere 333 homicides in 2012, the lowest number in the city’s recorded history.

New York City’s homicide rate has declined by 85 per cent since its peak in 1990, and is now lower than that of several Canadian cities such as Winnipeg and Regina.

The economic crisis, rising unemployment and growing inequality have failed to reverse the downward trend, although tough economic times are historically associated with increases in violent crime.

So what’s going on?

Fewer deaths = fewer shootings?

“I like to think we take some of the credit for that,” says Supt. Don Sweet, who is in charge of investigations for Ottawa police.

“I think we’re better at what we do. Investigating, interdicting and maybe stopping some of these things from occurring.

Ottawa Police Supt. Don Sweet says shootings are up, but homicides are down in the city. (CBC)

“We have our ROPE (repeat-offender parole enforcement) team, we have our high-risk offender management team, we have sexual offender registries, we have a DNA database.”

But Sweet said that Ottawa has seen an increase in shootings, even as its homicide rate has declined.

“I think there’s some medical reasons for that,” said Supt. Sweet about the homicide rate.

“Things have changed a lot, in the 25 or 28 years I've been in this business, where you have first-rate care being given right on the street, not only by paramedics but also by police and fire, that maybe wasn’t there 25 years ago. And they’re getting excellent care once they get to the hospital as well.

“There’s no doubt that we’re seeing medical care that’s helping people to live that wouldn’t have lived before.”

Trauma centres better at saving lives

The month of December in Ottawa brought some examples of how some gunshot and stabbing victims are surviving.

A man believed to be a gang member was attacked outside a restaurant and shot by two assailants with large-calibre handguns.

He was hit six times, including once in the head and twice in the torso, then rushed to the Ottawa Hospital and its level one trauma centre.

A man in his early 20s was shot multiple times at a restaurant on Ottawa's Industrial Avenue late Dec. 2. Dr. Jacinthe Lampron operated on him and he was released from hospital within days. (CBC) ​There he was operated on by trauma surgeon Lampron and released from hospital within days. JacintheLampron

“He’s probably up and walking, I have no doubt of that,” said Lampron.

“Full recovery? It would just depend how much traumatic brain injury he suffered from that, so he might have mild deficit, which should improve over time.”

A few days later another man was treated and released at the same ER after being shot in the head.

More than half of all people shot in the head now survive, though many have lasting impairments.

'Scoop and go' technique gets patients to hospital

The spread of specialized trauma centres in North American cities has perhaps been the single most important factor in reducing deaths from gun and knife injuries.

“Here we’re used to that,” said Lampron. “Everybody’s in a team, we’re waiting for trauma cases to come, and that makes such a difference. Anything that is specialized in medicine will have a better outcome.

Dr. Jacinthe Lampron worked at a Kandahar military hospital in Afghanistan before coming to the Ottawa Hospital. (CBC) "The team is really available, the OR is on standby and we’re ready to move there, the CT scan is on standby for us, the lab is on standby for us, so everything is kind of designed around it.”

Lampron said patients are also reaching ER faster. Paramedics are better trained, but have learned that speed in getting to the ER is the most important factor in survival of an injured person.

“They usually ‘scoop and go’ rather than ‘stay and play,’” she said.

The benefits of trauma centres, however, are typically only felt in major cities that can afford to have such specialized medical centres.

Homicide rates in Canada are traditionally highest in more remote areas such as Nunavut or the Northwest Territories, and those areas have seen fewer advances in trauma medicine.

Nunavut and the Northwest Territories had the highest homicide rates of any territory, state or province in the U.S. and Canada in 2012.

Both recorded homicide rates that exceeded those of the most violent U.S. state, Louisiana.

War brings change

Lampron is an army reservist who served in Kandahar’s military hospital as a civilian trauma surgeon under contract to the military.

Army medic Cpl. Darren Dyer stands watch on the front line in Panjwaii, Afghanistan. Techniques learned on the battlefield can help save patients at home. ((Les Perreaux/Canadian Press)) Her experience of war medicine is not uncommon among emergency physicians, and new techniques tested in combat have been behind many improvements in the treatment of injured civilians.

“Almost every war brought medicine higher,” said Lampron.

"The Second World War brought transfusion. The Korean War brought helicopter evacuation, but it also brought fluid resuscitation. I would say the last wars, Iraq and Afghanistan, probably brought what we call the ‘massive transfusion protocol.'

"So instead of giving lots of crystalloids, like a kind of watery fluid, we’re moving onto blood much sooner.”

Another innovation from the battlefields of the last decade was the use of tranexamic acid to slow bleeding, now common in civilian trauma centres.

Violence statistics not declining

Many people who might have become homicide statistics a generation ago are now mere victims of assault.

And that will inevitably have the effect of making society appear less violent, if violence is measured by homicide rates.

But Lampron said she doesn’t believe that society is becoming less violent.

“I have no insight on how things are going outside, but we feel we’ve been receiving more people recently injured by bullets. I would say over the years in general there’s more penetrating as well as gunshot [wounds] coming through the door,” she said.

“I think there’s more violent action towards people, that may not necessarily die, but I feel violence is going up in this city.”

One detail in Statistics Canada’s recent crime report seems to bear that out.

Although homicides and most categories of violent crime declined toward historic lows, the two most serious categories of assault remained higher than they were 10 years ago. From 2002 to 2012, the homicide rate in Canada declined 16 per cent, while the aggravated assault rate rose 16 per cent, according to Statistics Canada.

In the past, many of those aggravated assaults could have resulted in deaths and been counted as homicides.

U.S. figures also suggest that violence is not in decline.

The Centers for Disease Control estimated that the number of people who required a hospital stay after being shot climbed by 47 per cent between 2001 and 2011, from 20,844 to 30,759.

The CDC also counted a smaller increase in serious stabbings.

Yet during the same 10-year period, the annual number of homicides countrywide declined by eight per cent.