Yesterday in Pennsylvania, Hummelstown police Officer Lisa Mearkle was charged with criminal homicide. According to investigators, she initiated a traffic stop on motorist David Kassick on February 2, because he had an expired inspection sticker. She tased him first, and while he was lying face down in the snow, she shot him twice in the back, killing him. He was unarmed. The officer, who is claiming self-defense, has been released on $250,000 bail. Her version:

Authorities said Mearkle had attempted to pull over Kassick for expired inspection and emissions stickers before he sped away. She caught up to Kassick near his sister’s home where he had been living for a short time.

He got out and ran before Mearkle incapacitated him with a stun gun, held in her left hand. He was on the ground when she shot him twice in the back with the gun in her right hand, police said.

Mearkle, 36, told investigators she fired because he would not show her his hands and she thought he was reaching into his jacket for a gun. Perry said she did not know Kassick before the shooting.

The problem for her ‘I-thought-he-was-reaching-for-a-gun’ claim is that the taser apparently had a video recorder on it:

The stun gun contained a camera that recorded audio and video from portions of the encounter, and District Attorney Ed Marsico called it the strongest evidence in the case.

He said it appeared Kassick had been trying to remove the stun-gun probe from his back.

“At the time Officer Mearkle fires both rounds from her pistol, the video clearly depicts Kassick lying on the snow covered lawn with his face toward the ground,” according to the arrest affidavit. “Furthermore, at the time the rounds are fired nothing can be seen in either of Kassick’s hands, nor does he point or direct anything toward Officer Mearkle.”

Marsico said Mearkle waited 4 seconds between the first and second shots, and afterward performed CPR. He called the shooting “a tragedy for all involved.”

It’s amazing that a motorist can essentially be executed for expired inspection stickers, but David Kassick’s death- and the cop’s excuse- is both formulaic (‘I thought he had a gun’) and de rigueur- hardly a day passes without a headline somewhere in the US featuring an officer-involved shooting of an unarmed person. Will Officer Mearkle spend a single day in prison for incapacitating an unarmed motorist with a stun gun, then shooting him in the back, waiting four seconds and shooting him again, in the back? Probably not. They never do. In an article titled, “We’re asking the wrong question about police shootings,” Radley Balko  looks beyond whether the shootings are in line with some sort of departmental policy or even if the shootings are technically “justified” somehow. The right question is: Are they necessary?

But I recently spoke on a panel at the University of South Carolina with the former police officer and now law professor Seth Stoughton. He made a point that I think is critical in how we think about these incidents: We shouldn’t be asking if the police actions were legal or within department policy; we should be asking if they were necessary. Or if you’d like to use a word with a bit more urgency behind it, we should ask if they’re acceptable.

For instance, take a look at this unedited video of officers shooting and killing 38-year-old Jason Harrison, a mentally ill man, in Dallas last year:

Was that killing necessary? Is it acceptable?