I hadn't planned on writing anything about the tragic killing of Renisha McBride here. Not because it doesn't horrify me, but because the circumstances of her death, despite being in obvious respects horribly familiar, has specifics which are little difficult for me to get my head around.
And the way I tend to deal with things I can't quite figure out is to write about them, which in this case feels to me too much like a white guy talking about himself in regards to a black woman losing her life. Which is a problem.
But MightyGodKing is right, I think. White people do need to talk about this stuff, if only to make sure we penetrate the fog of indifference our culture still seems perfectly happy about wrapping ourselves in. A black person has been shot in America, again, and the police aren't sure whether it's worth arresting anyone, again. Trayvon Martin died because a man assumed wearing a hoodie whilst on the streets meant he was probably a criminal, and decided to give chase. Renisha McBride died because a man assumed knocking on his front door at 3:30am meant she was probably a criminal, and went to the door with a loaded shotgun.
That is - that has to be - the takeaway message in all of this. That black people in America live in a culture of paranoid suspicion that means that, even when we can't be sure race was the reason they were targeted, they can be damn sure race will be the reason nobody in authority will care.
There are, as I say, a few specifics here regarding gun laws and gun culture which I think might need unpicking, but as I say, it's a white British man pontificating on how a black American woman came to be shot for the crime of needing help with her car. So I'm putting it all below the fold. If you're interested, have at it, but if you want to stop reading here, I couldn't come close to blaming you.
I wonder here if there is going to be a similar problem prosecuting this case as there was with George Zimmeman's murder of Trayvon Martin. That is, it may turn out Renisha McBride's killer hasn't actually done anything legally wrong. He was well within his rights to approach his own front door with a loaded gun. I'm utterly in agreement with people pointing out the correct thing to do if he was concerned was call the police rather than Rambo up, but being appalled at someone's actions - as well as being a little problematic for someone living in an exceptionally nice and almost crime-free area like mine - doesn't translate into criminality.
I should think at the absolute barest minimum that if you're pointing a gun at someone and it goes off accidentally you should be charged with something, but in a country where at least two states let you kill someone for getting in your face or for stealing ten cents from you, I really don't know how that plays out.
The obvious point to be made here - as Imani Gandy has made, among others - is that such legal pedantry wouldn't matter two shits if McBride had been white and her shooter had been black. As ZandarVTS said on Twitter, that guy wouldn't even have made it to the police station; within ten minutes he'd have more holes in him than Zimmerman's defense . But it may be - I'm clearly no expert on Michigan law, and as yet I've not seen anyone address this - that the shooter literally did nothing legally wrong, and it's the arrest and conviction of black people who should be protected by the same lunatic laws (as frequently happens, as it does when it's women doing the shooting and are aiming at - or just warning - abusive husbands) is where the police are acting inappropriately within their framework. 
(All of that, though, bypasses the issue of why the police decided to immediately accept the shooter's claim that the shotgun went off accidentally. Again, maybe this is standard policy in the insane system these hideous laws have generated. Maybe it isn't.)
In short, then: there are laws out in the various states that are abominable, that prioritise paranoia and the worship of weaponry over public safety, and which are racking up body counts because the deaths of people politicians were never going to meet at garden parties in any case has somehow just become the cost of doing business these days. It may even be that these laws have reached such horrendous lengths that the police can't even justifying the arrest of someone waving the seemingly iron-clad excuse of "protecting my home", as long as it comes alongside an explanation no-one can ever possibly disprove (not for nothing did people note acerbically that Zimmerman's acquittal was possible in no small part because the only witness who could contest his version of events had been shot to death, by him).
If all that is true - and if it isn't, there are some damn good questions the DPD need to answer, and they need to do it fast - the real horror here might not be that the Detroit Police are institutionally racist. It might be that they didn't even need to be.
 For those who don't follow American politics as closely as I do, you may be horrified to know that not only did Zimmerman start touring to promote the very make of gun he used to kill Trayvon Martin, but that his wife has accused him of threatening to shoot her during a domestic argument. The right in America choose the strangest heroes.
 With the contemporary Republican Party having utterly lost its mind, even more so on the state level than in Congress, I really don't see how any of this gets dealt with until the immovable object of "We have a right to our guns" finally faces the unstoppable force of "The blacks are coming for us!" head on. How that particular battle goes down is anyone's guess, but I hold out no hope it won't be ugly.