That guidance comes from a lengthy report released in summer of 2020, following a two-year review of weapons used against crowds. The U.N. authors further advised that "the results of monitoring should be made public," and the suggestion seems wise.
After all, you can't fix a threat to public safety -- including the threat of costly, disproportionate and disfiguring disability meted out at the hands of police -- unless you understand its prevalence.
Until this month, the dozens of injuries sustained by members of the public as a result of so-called "non-lethal weapons" used on civilians during protests last summer had yet to be formally compiled in Minnesota.
The first of those reports is now out, albeit with no help from Minneapolis or Minnesota state health officials. It turns out the weapons are not so "non-lethal" after all.
"We were seeing a lot of injuries to the face and the head that required some surgery and caused some blindness," says Dr. David P. Darrow, a neurosurgeon at M Health Fairview and Hennepin Healthcare Systems hospitals in Minneapolis.
"This seems pretty extreme to us, especially since many of the people injured were just bystanders, not even in the protest."
Darrow and his 14 co-authors compiled a database of injuries treated at the two hospitals in connection to less-lethal weapons like kinetic impact projectiles, and tear gas. They published that work in mid-January as a letter to the New England Journal of Medicine.
It reported 89 such injuries at the two systems, 45 from projectiles, 32 from tear gas, and 12 from both. The injuries included 41 from from rubber bullets, seven from tear gas canisters, two from bean bags and seven from unknown projectiles.
The study noted 16 patients in Minneapolis received traumatic brain injuries, conditions potentially requiring long-term rehabilitation and capable of causing permanent disability.
The munitions hit 10 Minneapolis protesters in the eye, leaving three permanently blinded in one eye as a result.
"We were surprised to see that 40 percent of the impact injuries were to the head, face and neck," says Erika Kaske, a medical student at the University of Minnesota and coauthor on the paper. "That's pretty high when you look at guidelines that say, basically, that shots to the head, neck and face are potentially unlawful."
The 2020 U.N. report addresses this potential illegality under a heading titled "Circumstances of Potentially Lawful Use."
"Kinetic impact projectiles should generally be used only in direct fire with the aim of striking the lower abdomen or legs of a violent individual," it reads, "and only with a view to addressing an imminent threat of injury to either a law enforcement official or a member of the public."
Law enforcement in Minneapolis appears to have faced safer travels during the violent quashing of protest.
Though they did not publish the information, the University of Minnesota clinicians collected data denoting who was treated in their systems during the period of protest, and while the events are commonly described as a "riot," the physical harm from that rioting fell almost entirely on the public.
"In terms of the police that were injured," Darrow said, "it was only a handful, and it really didn't compare to the protesters."
The authors also noted a striking disregard for safety on the part of Minneapolis police with the firing of tear gas canisters.
"We saw injuries from the tear gas canisters as projectiles," said Darrow. "That's what's so disturbing. Even if you say, 'we're just going to use tear gas,' the problem is, they're being shot into people's heads."
"These things are heavy weapons. They can cause serious harm as a projectile."
Repairing injuries caused by the global incidence of police brutality seems to fall heavily on neurosurgeons. Last June, the journal World Neurosurgery published gruesome CT scans of the heads of 10 protesters, all in their teens, killed by having a tear gas canister penetrate their skull at the hands of crowd control officers in Iraq.
The U of M study is only the second effort to systematically collect data on health impacts of non-lethal weapons used in crowd control following protests over the death of George Floyd.
In September, clinicians from the University of Texas at Austin reported that so-called "bean bag" munitions, which are supposed to cause minor blunt injuries only, required seven surgical operations, four because a bean bag had penetrated the body.
Also, four patients in Texas had brain hemorrhages from bean bags, and one had a skull fracture that required intubation, brain surgery and 23 days in the hospital followed by discharge to a rehab facility .
"That is a serious injury," says Dr. Kristofor Olson, surgery resident at the University of Texas at Austin, on-call trauma resident at the hospital during the Floyd protests, and coauthor on the letter.
"You hear the phrase 'bean bag' and it seems kind of cartoonish. You imagine something people would use in yard games, that would bounce off a person and not cause a penetrating injury. These were injuries that seemed a whole lot more like shotgun wounds."
"They were lodged in people," he says. "One of them, the bean bag broke up and she had the shot retained in and around her elbow. One had the bean bag launched through her armpit and into the tissue below her breast, right there on her chest wall."
"Two individuals had bean bags that actually caused fractures and depressions in their skull. One actually had a bean bag retained in her forehead, not all the way to the brain but it had penetrated the skull."
Austin quickly banned bean bag munitions -- fabric bags around lead shotgun pellets -- and the injuries dropped off. Both sites believe it is incumbent on health officials to collect data on injuries sustained in policing actions against crowds.
"I think it's important to highlight the severity of these injuries that we witnessed, and that the folks in Minneapolis witnessed," Olson said. "I do not think this is unique to our two cities. I think it's happened throughout the country, and it's an important discussion for us to have."
"Aside fomo the publication in Austin and ours," Darrow says, "no other protests in the U.S. have been evaluated like this in the past 10 years. There's been nothing on this and that has been really disturbing to us."
Darrow says the next step is to try to gain similar information from other city hospital systems during the same period. The surgeon said there has been a lack of participation so far from officials from the City of Minneapolis, the Minnesota Department of Health, office of Gov. Tim Walz or public safety.
"The larger discussion is the connection between public safety and public health," he says. "At this time, there's not a lot of dialogue ... so that they understand what they did during these protests. There's no discussion about what the guidelines should be."
"As far as I know, nobody from any city department has talked to us about that. We're going to move forward and try to talk to them about it."