Constitutionally, "police officers are allowed to shoot
under two circumstances," says Klinger. The first circumstance is "to
protect their life or the life of another innocent party" — what
departments call the "defense-of-life" standard. The second circumstance
is to prevent a suspect from escaping, but only if the officer has
probable cause to think the suspect's committed a serious violent
felony.
cops can't shoot every felon who tries to escape
The logic behind the second circumstance, says Klinger, comes from a Supreme Court decision called Tennessee vs. Garner.
That case involved a pair of police officers who shot a 15-year-old boy
as he fled from a burglary. (He'd stolen $10 and a purse from a house.)
The Court ruled that cops couldn't shoot every felon who tried to
escape. But, as Klinger says, "they basically say that the job of a cop
is to protect people from violence, and if you've got a violent person
who's fleeing, you can shoot them to stop their flight."
Some police departments' policies only allow deadly force
in the first circumstance: defense of life. Others have policies that
also allow deadly force to prevent escape in certain cases, within the
limits of the Supreme Court decision.
Does the convenience store robbery matter?
Shortly after releasing the documents that identified Brown
as the primary suspect in a convenience-store robbery, the Ferguson
Police Department clarified that Wilson had not known that Brown was a
robbery suspect when he made "initial contact" with Brown and his friend
Dorian Johnson. (Instead, the department says, Wilson stopped the
teenagers because they were walking in the middle of the street.)
That phrasing doesn't make it clear whether or not Wilson
believed Brown to be a robbery suspect when he started to shoot at him.
If he did, it might then be up to the investigators and county
prosecutor McCulloch to decide whether a "strong-arm robbery," as the
Ferguson Police Department described the incident, counts as a violent
felony. If they decide it does, that will go some way toward a legal
justification for Wilson's action. On the other hand,
Wilson would only be able to claim that he was justified if Brown was
fleeing — which eyewitnesses say he wasn't.
It's most likely, however, that the whole question is moot.
From the Ferguson Police Department's statements on the afternoon of
August 15th, it doesn't sound like Wilson even knew about the robbery at
all. In that case, there's no way for him to claim that he was
justified in keeping a violent felon from fleeing, because he didn't
even know Brown was a suspect in a crime at all.
Wilson could instead, however, claim "defense of life"
— that he feared for his life when Brown (according to his story)
assaulted him in his car. In that case, the next question will be
whether it was reasonable for him to be afraid of Brown.
