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Why is it so hard to prosecute police? It starts with the investigation.

Police are protected by a mix of policy and culture from the very beginning.

Former Minneapolis police officer Derek Chauvin (center) is taken into custody after being found guilty for the murder of George Floyd.
Court TV via AP

When a jury found former Minneapolis police officer Derek Chauvin guilty of murdering George Floyd, it did something very unusual. The reality in America today is it’s notoriously difficult to prosecute police officers for killings — less than 2 percent of fatal shootings are ever prosecuted for murder or manslaughter, and even fewer are convicted.

That difficulty begins with the immediate aftermath of a police officer killing someone: The event is investigated by the police themselves, who have very different incentives than they do during a typical criminal investigation.

You can probably conjure up images of a crime scene from shows like CSI or Law & Order: Police descend onto the scene, gathering evidence down to the molecular level. They talk to any witnesses. Officials from other offices — prosecutors in particular — might be present to get an early lead on where the investigation could go.

Everything is geared toward not just figuring out who committed the crime, but making sure that, if charges are brought, they can be proved beyond a reasonable doubt in court.

As Philip Matthew Stinson at Bowling Green State University previously told me, things look very different after an officer kills someone. Most importantly, the underlying attitude in the investigation is not to prove the officer did anything wrong but in many cases the opposite: to help a fellow colleague prove that the killing was explainable, if not justified.

To the extent the scene of the killing is considered a crime scene at all, police are often focused on whatever crime the victim allegedly committed.

So while the scene of a killing typically involves collecting evidence to prove that the individual was responsible and committed a crime, an investigation into a police killing aims to find evidence that the victim did something wrong and that the officer’s actions were justified.

While murder investigations typically try to get witnesses on the record as quickly as possible, in police killing investigations officers who kill someone are usually given days — sometimes under the law — before they take an interview.

If officers witness a crime, they’ll usually testify; in a police killing investigation, there’s a no-snitching code known as the “blue wall of silence” that encourages officers to not talk and to avoid incriminating their colleagues in any way. Investigators — themselves police — will readily accept and encourage all of this, seeing themselves as part of the team.

A 2000 study, published in the National Institute of Justice Journal, found that murders are much more likely to be solved when police are faster at securing a scene, notifying homicide detectives, and identifying witnesses. Each step in a police killing investigation can go in the opposite direction — which would be considered an unacceptable blunder in just about any other criminal investigation.

“Everything is done different” than in a typical murder, Stinson said. “It makes it difficult for prosecutors to figure it out and to make a rational decision, an informed decision, in terms of charging.”

Difficulties in the investigation trickle down to prosecutors’ work

The differences continue as the case progresses from the officers' and detectives' level to the prosecutor’s office, which is in charge of building the case if it goes to trial.

For one, prosecutors have incentives to not push police too hard. They work closely with police on a day-to-day basis — they need officers to swarm at that typical murder scene, gathering evidence needed to prove a case. If prosecutors go after the police, officers could retaliate by slacking at their jobs — not unheard of, as cases of “blue flu” attest to — and leave the prosecutor unable to do their job in court.

If prosecutors do push ahead with an investigation into an officer, though, they’re much less likely to get cooperation from the police, as that blue wall of silence rears its head again.

This isn’t theoretical. After the 2017 Minneapolis police killing of Justine Damond, Hennepin County prosecutor Mike Freeman complained he could not get much cooperation from officers to prove the charges against the shooting officer, Mohamed Noor. Although Noor was ultimately convicted and sentenced to prison, the path to get there was difficult.

“A number of the officers, for reasons we do not understand … refused to come answer questions,” Freeman said in 2018. “I’ve been privileged to have this job nearly 18 years, I’ve never had police officers who weren’t suspects refuse to do their duty and come forward to talk to us.”

That’s if a prosecutor seeks charges at all. Knowing the hurdles involved from the start, a lot of prosecutors don’t pursue these cases to begin with.

The collision of policy and culture protects police from the start

This kind of dynamic — in which the law, policy, and culture work together to protect police — helps explain why officers are prosecuted for murder or manslaughter in less than 2 percent of fatal shootings, based on Stinson’s data. Many, perhaps even most, of the shootings are justified, as a police officer was in genuine danger or had the legal right to use lethal force. But Stinson said he’s skeptical that the correct rate of justified shootings is really less than 2 percent: “In my opinion, it’s got to be that more of the fatal shootings are unjustified.”

Policy could help. From the start, officers could be guided to not approach police killing investigations with a bias toward letting their colleagues go free. The law could be changed to raise the standard for when use of force is justified. Putting independent prosecutors, who don’t have a direct relationship with the officers being investigated, in charge of cases could help.

But as the beginning of a police investigation makes clear, much of the problem is cultural. At some level, fellow officers have to be invested in holding one other accountable. Other actors in the justice system, policymakers, and the public have to expect it from police, too. This might require complicating the image of all police officers as unquestioned heroes who always do the right thing.

Otherwise, investigations into police officers will go wrong from the very start. And verdicts like Chauvin’s will remain rare.

For more on why it’s difficult to prosecute police, read Vox’s full explainer.

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