Paul Butler is the Albert Brick Professor in Law at Georgetown University. A former federal prosecutor, he is the author of “Chokehold: Policing Black Men.”

Former Minneapolis police officer Derek Chauvin has finally been arrested for the murder of George Floyd. Now comes the hard part.

As the case against him moves from the court of public opinion to the Hennepin County District Court, prosecutors will face significant challenges in securing a conviction. To many, the third-degree murder and second-degree manslaughter charges filed against Chauvin seem insufficient, understandably so. My assessment, as a former prosecutor who specialized in cases involving corrupt law enforcement officers, is that they represent a reasonable step on the road to justice.

Good morning ladies and gentlemen of the jury. Eight minutes and 46 seconds. That’s how long Derek Chauvin kept his knee on the neck of George Floyd, while Floyd said over and over “I can’t breathe” as the life drained from his body.

Two minutes and 53 seconds. After Floyd’s body went limp, and another officer could not detect a pulse, that’s how long Chauvin continued to use his knee to compress Floyd’s neck.

Chauvin was charged after videos showed him with his knee on Floyd’s neck, ignoring Floyd’s cries and bystanders’ pleas to stop. He was taken into custody after protests across the country. As a black man, I didn’t know it was so hard to get arrested.

As a former prosecutor, though, I am well aware of the difficulty of convicting a police officer. The odds are against it. Since 2005, approximately 100 officers have been charged with homicide for using deadly force in the line duty. But most of those officers walked; the charges were dismissed or they were acquitted.

As of 2019, there had been only 35 convictions, almost all for manslaughter or negligent homicide, not murder. Cases with police officers as defendants stand in stark contrast to cases with civilian defendants, where prosecutors win trials or obtain guilty pleas in upward of 90 percent of cases.

Prosecuting an officer is fraught from the beginning. The “blue wall of silence” means that other police officers, often the main witnesses, are frequently uncooperative or hostile. Supreme Court rulings governing use of deadly force encourage jurors to evaluate the evidence from the perspective of the police officer.

Even when jurors are convinced a crime was committed, they are often reluctant to convict because they think it’s unfair to punish police officers for making mistakes when trying to do their jobs.

In light of these hurdles, the decision about what crime to charge is crucial.

Crimes are divided into two elements: act and intent. The act requirement in homicide is causing a death. Even this is likely to be an issue in the Floyd case, because the coroner’s report indicates Floyd had preexisting conditions that may have contributed to his death. There is likely to be medical expert testimony on both sides, but the jury should use its common sense: it’s highly unlikely that Floyd just happened to die while Chauvin was pressing on his neck, a risky technique banned by many departments.

Proving intent is more difficult. The punishment for homicide is based on what the defendant’s mind-set was at the time of the death. People who kill accidentally, such as drunk drivers, are usually charged with negligent homicide. People who kill in the heat of passion or recklessly are guilty of manslaughter. Murder is the most serious grade of homicide.

Benjamin Crump, the attorney for Floyd’s family, has said the family “expected a first-degree murder charge” and that the charges should be increased to “reflect the true culpability of this officer.”

But under Minnesota law, to win a first-degree murder case, the prosecutor would have to prove that Chauvin intended to kill Floyd. For third-degree murder, the jury must only find that Chauvin’s actions were “eminently dangerous” and displayed “depraved” indifference to human life. That’s why I would start by describing the unspeakable cruelty of Chauvin crushing the life out of Floyd while Floyd narrates his own demise, calling out for his deceased mother and asking Chauvin to “please, please” release him.

Then I would go to the videotape. No case against an officer is a slam dunk, but prosecutors rarely have the quality of evidence they have here.

I am sympathetic to the desire to see punishment that reflects the gravity of the crime. First-degree murder in Minnesota carries a life sentence; 25 years is the maximum for third-degree murder. But police officers don’t usually get the maximum sentence in any case.

And a convicted murderer is a convicted murderer. That is far more likely with the third-degree charges because the prosecution has less to prove.

Meanwhile, there are risks on the other side. An acquittal in a case like this would be a crushing defeat not just for the prosecutors, but for all Americans who hope to see justice done. This is a case that prosecutors must win — and a third-degree murder conviction is better than no conviction at all.

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