Improved community bonds and gun control that limits the amount of firepower that people can access would increase both police and citizen safety, a Stanford scholar said.

Stanford News Service recently interviewed John J. Donohue III, a law professor who has been conducting empirical research on gun violence and gun control for more than 25 years. Donohue is the C. Wendell and Edith M. Carlsmith Professor of Law at Stanford.

When and how can the police legally shoot and kill a person? Are there federal and state differences?

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Police use of deadly force is typically constrained by both applicable state law and by the United States Constitution. While there are some state law differences, they tend to be less important than the attitudinal differences that exist in various regions of the country that may lead prosecutors and juries to reach different conclusions based on their differing worldviews. In general, the more dangerous the crime that the officer believes someone to have committed and the greater the threat to safety the individual poses, the greater the ability of the police officer to use force, including deadly force.

As the Supreme Court stated in Graham v. Connor [1989], “All claims that law enforcement officers have used excessive force – deadly or not – in the course of an arrest, investigatory stop, or other ‘seizure’ of a free citizen should be analyzed under the Fourth Amendment and its ‘reasonableness’ standard.” The Supreme Court went on to stress that “the ‘reasonableness’ of a particular use of force must be judged from the perspective of a reasonable officer on the scene, rather than with the 20/20 vision of hindsight.”

Do the data show a rising or falling number of police-initiated deaths of citizens?

The FBI publishes annual figures that are said to capture the number of incidents in which the police justifiably kill a citizen. This data on killings by police is of very poor quality, however, because the FBI simply publishes whatever police departments voluntarily give them. Not surprisingly, then, the FBI counts of such deaths are far below the actual counts, but I estimate the proper number is in the neighborhood of 1,000 to 1,500 per year. The imperfect data may still give us an insight into the trend in killings by police, and the trend shown in the data has been down. I suspect that police killings of civilians are in fact down from the early 1990s, as the FBI data suggests, because overall crime rates have fallen substantially since that time.

The FBI does a good job of collecting information on the number of police that are killed in the line of duty, and this number is now at an all-time low of roughly 62 officers killed per year out of roughly 800,000 sworn officers, down steadily from about 101 annual police deaths during the Reagan years. This is not purely the result of better body armor and medical treatment, because the number of assaults per 100 police officers is also down from 12.7 in 2000 to 9.0 in 2014 – the last year for which we have data.

What can be done in terms of legislation or policy to prevent these types of shootings?

In a country with massive prevalence of guns, police are always aware that they are in danger, and as noted above, even though assaults on the police are down, they are still at a distressingly high level – about a 10th of the police force is assaulted every year. The primary cause of death to police officers from intentional assaults is from guns. Efforts to improve officer safety through body armor and effective training can lessen the threat they feel and thereby reduce the number of “quick trigger” events. Unfortunately, the relationship between the community and police is often one of confrontation and disrespect, which is unhelpful to everyone. The community often needs to better understand that the police overall play an enormously important role in reducing crime and thereby making everyone safer.

At the same time, police officers who harbor prejudice against certain members of the community or who are overly sensitive to perceived slights from the public are highly counterproductive and increase the prevalence of illegal misconduct. Better police training and hiring practices are two obvious ways to reduce the use of excessive force overall and deadly force in particular. As one might expect, a relatively small number of police officers generate a disproportionate number of problems, and the behavior of these outlier officers needs to be changed or they should be eliminated from the police force. Body cameras on police officers can be effective in restraining misbehavior of both the police and the public.

Finally, as we saw in Ferguson, Missouri, cities that intentionally structure their police force to use ticketing of civilians as a way to finance their operations will necessarily court trouble, and systemic reform is needed wherever this behavior is prevalent.

What can enhance police safety, given the events in Dallas?

Reducing civilian firepower is an obvious measure to enhance police safety, as is banning armor-piercing bullets, although both of these measures are strongly resisted by the NRA [National Rifle Association]. The measures enumerated above that are designed to promote better relations between the police and community – as well as any measures that lead to lower crime rates – will also be helpful.

One important study that merits further investigation found that states with high rates of civilian gun ownership are more dangerous for the police. The study examined data on the number of homicidal deaths of police in two groups of states with roughly equal number of police officers – the eight states with the lowest levels of gun ownership and the 23 states with the highest rate of gun ownership. The study found that, over the period from 1996 to 2010, the rate of police homicide in the high-gun prevalence states was three times as high as the rate of police homicide in the low-gun prevalence states.

What is the trend overall on murder by guns in the U.S.?

Overall, crime is down substantially from the peaks of the early 1990s. This includes overall murder rates and gun murder rates. Still, even with this improvement, our murder rates are far higher than those in other affluent countries, and this is largely explained by the higher rate of gun homicides. Lamentably, preliminary data for the 50 largest cities suggests that the murder rate in these large urban areas rose by almost 17 percent from 2014 to 2015, which is still considerably below the level of 25 years ago.

Despite the improvement since the early 1990s in overall crime and murder rates, there does seem to be a sustained upward trend in mass shootings, which are more frequent, and with each episode more deadly, since the end of the federal assault weapons ban in 2004. While the total deaths in these mass shootings is small relative to the overall homicide rate, mass shootings are particularly high-visibility events and are quite shocking to the public and unsettling to the sense of public safety.

What do you think of California’s new gun control measures?

California continues to lead the way in trying to reduce the number of gun homicides, suicides and accidents, and should be highly commended for doing so. The state now has the ninth lowest overall gun death rate of any state nationwide, when in the early 1990s, it had the 35th lowest rate. Over the last 15 years, the firearm death rate in California has fallen by roughly 20 percent while the national rate has largely been unchanged. One of the new measures is to fund research that could clarify how California has been able to achieve this reduction, which should provide useful information for all states.

The latest gun control measures are designed to continue this progress. For example, one measure will make it harder for prohibited purchasers – felons, domestic batterers and the severely mentally ill – to use their guns by requiring background checks for ammunition. Two other measures – the new ban on high capacity magazines and prohibition of enabling the easy conversion of lawful guns into assault weapons – represent additional moves in the right direction. A fundamental principle is that civilians should have no more firepower than is demonstrably needed for lawful purposes.