When does a horrible mistake become a crime?

One mild winter's evening three or four years ago, I stopped as I occasionally do at a lakeside park near my home. I found a seat out of the wind on a bench by the side of a small park building and watched some ice skaters swirling in the moonlit distance.

After a minute or two, a sheriff's deputy pulled his squad car into the parking lot. The park is officially closed after dark, and I figured he planned to remind me. Not seeing anyone in my car as he pulled up, he quickly stepped out and started looking around with his flashlight.

I wouldn't say it was a tense moment. But it was slightly awkward sitting there in the shadow of the building 30 feet from an armed cop searching the area, wondering what was up. I didn't puzzle about what to do for more than a moment, but I guess something told me not to just step out of the darkness and surprise him. So I spoke up from where I was:

"Officer, I'm over here against the building" — or something like that.

He turned his light in my direction, quickly checked me out, then walked over and pleasantly advised me that the park had closed at sunset.

I've been reminded of this otherwise forgettable encounter as I've followed daily reports of the trial of former Minneapolis police officer Mohamed Noor. No doubt I'll be criticized for blaming the victim by unearthing the memory in connection with the heartbreaking shooting of Justine Ruszczyk Damond. I regret any hint of that.

But I can't help wishing Damond, a perfectly innocent victim, had felt the same unreflective instinct I did that evening at the park — that startling a cop was something best avoided, even in a low-stress situation. There had been no report of violence in that lakeside parking lot that night, I'm quite sure.

But Damond, as anyone following the Noor case knows, had summoned police with a 911 call on July 15, 2017, reporting what sounded like a sexual assault in the alley behind her southwest Minneapolis home. When she approached the stationary squad car in which Noor and his behind-the-wheel partner had searched the length of the alley, the young Somali-American officer shot the pajama-clad Damond through the open driver side window, killing her.

What's emerged from several weeks of trial testimony, according to vivid and detailed reporting from the courtroom, especially from Star Tribune reporters Chao Xiong and Libor Jany, is a painful story of two young cops becoming frightened, and of one of them reacting catastrophically by hurriedly firing off a shot at the utterly harmless citizen who had sought their help. Prosecutors have argued that nothing about the circumstances justified the officers feeling so threatened as to make the shooting reasonable.

A good deal of the trial has reportedly been consumed with disputed details about confusion and conflict among responders and investigators the night of the shooting and long afterward — although what these controversies reveal about Noor's guilt or innocence is often unclear. Tension over the case between prosecutors, police and investigators has been on display at least since December 2017, when Hennepin County Attorney Mike Freeman made and later apologized for secretly recorded criticisms of investigators in the case.

More relevant to the charges against Noor has been disputed testimony about whether some kind of bang or slap on the vehicle alarmed the officers just before the shot was fired. Meanwhile, testimony has indicated that the scene was not particularly dark.

It appears the puzzle of how to judge a panic that inspired a disastrous and deadly misjudgment will be the one Noor's jury will have to solve.

With Noor's emotional testimony last week that his training taught him decisive action was the key to survival for oneself and one's partner, along with dueling expert testimony over standards for police use of force, it seems the decision may come down — as it often does in a case involving police violence — to determining when a horrible mistake becomes a crime.

We send police officers in harm's way, and of necessity authorize them to use reasonable force to protect themselves or others, knowing this inevitably runs the risk of blunders and of innocents sometimes being hurt.

How "unreasonable" does an errant use of force have to be to become a criminal act?

Noor is charged with second- and third-degree murder and second-­degree manslaughter. These serious charges involve differing states of mind toward the death one caused — different levels of "intent"; a "depraved mind, without regard for human life"; or "culpable negligence."

In a landmark 1989 case (Graham vs. Connor), the U.S. Supreme Court handed down often-cited guidelines for judging reasonable force by police. The court emphasized that the question is whether a given use of force was " 'objectively reasonable' in light of the facts and circumstances confronting [the officers]" — even if the force used "may later seem unnecessary in the peace of a judge's chambers." Allowance must be made, the court said, "for the fact that police officers are often forced to make split-­second judgments — in circumstances that are tense, uncertain, and rapidly evolving … ."

Reasonableness itself does not depend on a cop's attitude, the court said: "An officer's evil intentions will not make a … violation out of an objectively reasonable use of force; nor will an officer's good intentions make an objectively unreasonable use of force constitutional."

In the end all this may make only two things clear, heading into the climactic days of the Noor trial:

First, the difficult standard of proof sheds light on why prosecutions of cops for line-of-duty killings are rare. Indeed, they're rare enough to make the unusual racial configuration of this case hard to ignore. Had it been Officer "Moe Nordlund" called that night to investigate a possible rape in a north Minneapolis alley, who mistakenly shot a young black woman who'd unexpectedly walked up from behind — would we be in exactly the same place with this case?

Let's hope we would; let's hope facts have been and will be what counts. Because the second thing that seems clear is that our community — or rather, our communities — may need to prepare themselves for almost any outcome.

D.J. Tice is at Doug.Tice@startribune.com.