The Missouri Loophole
New Republic reporter Yishai Schwartz points out the central problem with prosecuting Ferguson police officer Darren Wilson for the Michael Brown shooting: Under Missouri law,
you're pretty much allowed to shoot anyone.
[W]e expect situations of justified violence and legal killing to be the rare exception, and most people would probably imagine that policemen and citizens raising claims of justifiable homicide must meet a substantive burden of proof. But in Missouri, these justifications barely require any evidence at all. [...]
Instead, as long as there is a modicum of evidence and reasonable plausibility in support of a self-defense claim, a court must accept the claim and acquit the accused. The prosecution must not only prove beyond a reasonable doubt that the defendant committed the crime, but also disprove a defendant’s claim of self-defense to the same high standard. Under Missouri law, all a citizen claiming self-defense or a police officer claiming to have fired while pursuing a dangerous criminal need do is “inject the issue of justification.” In other words, he only needs to produce some evidence (his own testimony counts) supporting the claim. Once he does so, “any reasonable doubt on the issue requires a finding for the defendant.”
This isn't specific to law enforcement officers, mind you; citizens get to make the same claims. Prosecutors don't just have to prove you killed someone, they need to prove that your justifying self-defense scenario could not have happened
beyond a reasonable doubt, and if your only claim is "he was coming right for me," they have to prove
beyond a reasonable doubt that you were lying about that. It's all very Stand Your Ground, which may or may not be one of the reasons that St. Louis remains a hellhole. Sorry, I mean "faces challenges."
Schwartz calls the case against Wilson "basically impossible." That seems extreme; there are numerous witnesses all telling the same story, and that story seems to disprove a self-defense claim, but the deference given police officers over even multiple neighborhood witnesses could very well constitute the necessary reasonable doubt. Especially when the prosecutor himself has a similar history of being deferential to the claims of law enforcement.