When Police Kill is an important, groundbreaking book by Franklin E. Zimring. It is an absolutely necessary book that addresses the data shortcomings that will frustrate any attempt to address the incomparably high rate of killings of civilians by police in the United States, the relative impunity with which police kill civilians, and the negligible and ineffective efforts to curb the frequency of those killings. It is also a rigorously academic book steeped in statistics and careful, painstaking analysis–a necessary attribute when the subject is so highly charged and fraught with conflict.

Of course, one reason this is such a fraught topic is that uncontested data is simply not available. Data collection is haphazard and no local, country or state law enforcement agencies are compelled to report killings to the federal government. Without compulsory reporting, it’s not surprising that those places that do collect this data vastly undercount police killings by half. After Ferguson, when the media realized the federal government did not track this data accurately, the Washington Post and the Guardian both collected their own database based on news reports of police killings. Even there count may undercount killings as many local and regional papers do not report anything more controversial than the winner of the annual betting pool to pick the day a junker car falls through the ice at the local lake. Nonetheless, it’s clear by their data that there are a minimum of 1000 people killed by police each year–more than three per day. When other countries have two or three or five, you can see how wildly disproportionate police killings are in the United States.

Zimring looks at what factors are most common in situations when police kill, things like how many police are on the scene, how many shots were fired, what rationale for killing was used. Surprisingly, since the public often believes police kill to protect the public, only 2.7% of police killings happened to protect others. They were overwhelmingly cases where the police cited fear for their own safety, though whether that fear is reasonable is what is often the heart of heated public debate.

Zimring, to be fair, looks at how often police are killed by the public as well. He notes that the number of police killed has gone down dramatically, less than a quarter of what there used to be, but there has been no comparable decrease in police killing civilians. Police are measurable and objectively safer, but seem to be subjectively in just as much jeopardy. Zimring attributes much of that to so much of police training and standards being based on non-peer reviewed and never-tested standards such as the 21-foot rule that says never let someone with a knife within 21 feet. It’s a made up rule, taken as gospel, and used to justify several killings ever year and never tested. Police training and practice guidelines are rife with this sort of tradition that has never been empirically tested.

Zimring looks at every aspect of police killings, from the number, the situational attributes, costs and post-shooting accountability and then offers several reform suggestions that make a lot of sense. Most particularly, he advocates an end to local jurisdictional investigation and prosecution (if there is prosecution) in police killings, pointing to the conflicts of interest that inherently govern local investigations. He suggests there be three police-specific federal crimes, voluntary manslaughter with appropriate mitigating or aggravating circumstances,  excessive use of deadly force, and knowingly obstructing a deadly force investigation, a way of finding accountability for those officers who are complicit in covering up wrongful deaths with false statements and so on. He does not, however, think criminal prosecution of police will ever do much to reduce police killings. Instead, he argues that the most effective way to stop police from killing people is for the local chief of police or sheriff to tell them to stop killing people.

Police departments should have use of force guidelines and many are too lax, allowing inappropriate use of force that result in the deaths of civilians. Could it really be so simple?

In When Police Kill, Zimring is taking on one of the most hotly contested and irrationally polarized conflicts in American polity? How is it that the party of anti-government distrust and dislike who fears government suggesting what kind of health insurance benefits you should have is perfectly okay with government employees shooting people with impunity? On the other hand, how is it that the party that wants to reduce the flood of handguns in the hands of untrained, unlicensed civilians does not realize that the flood of guns exacerbates the fears of police officers? Some, not all, of their fear is justified by the rampant availability of guns.

Zimring is scrupulously careful to avoid hyperbole or to move into polemic. I suppose that is a good thing since his goal is to influence policy and the people who must be influenced are the chiefs of police, the country sheriffs, and those in police departments who write use of force policies. However, that does make this a very dry book that requires effort to keep reading. The scrupulous consideration of data and the multiplicity of charts to examine data from multiple lenses can be mind-numbing. Yet, it is that stern discipline that in the end gives his analysis authority.

This is not an easy book. Sometimes it slows down to agonizing specificity and drowns you in details, but the point of this book is not to entertain. The idea is abhorrent. This is a book dedicated to finding the facts and it succeeds. The second purpose is to recommend policies and reforms that would reduce the number of killings by police without endangering police. It succeeds. There is another, unspoken, goal, treading the thin border between advocating for greater accountability for police who kill and not alienating the people whose active participation is required to make change. I do not know how well he threads that needle, since many in law enforcement are hostile to any accountability at all, but he made a serious effort.

If you are interested in police reform, knowing the facts is important–particularly when they are much worse than we thought. Knowing what kinds of reform have the greatest impact, where reform is most possible, and recognizing the institutional barriers to accountability are all important. I think this is a must read for anyone interested in police reform.