It shouldn't but we've seen this time and again. Young black person killed by older white male. First thing they do is start taking apart every bit of that black person's life. Trayvon was a 'thug', so and so had a bad grade in 7th grade algebra, McBride was drunk. In the eyes of a jury; which will almost certainly have no blacks, since defense attorneys argue that blacks can't be impartial with these kind of matters but whites can, she will be seen as the perpetrator. A welfare queen/baby mama drain on society who was out partying and drunk driving.
You know who else was arrested for driving under the influence? The last President of the United States. A hiccup on his record, a capital crime on hers.
Anytime a prosecutor takes their sweet time with this kind of stuff, it's a sign that nothing's gonna happen. The chances of this dude going in front of a jury before were slim. It's almost zero now. Even if they WANTED to prosecute him (it's clear that they don't), they only have to have 1 person on the jury with an unconscious bias (that the defense will surely try to develop even in unbiased jurors) and the guy gets off.
It is very cut and dry. They know who shot her. They know she wasn't committing a criminal act. They know she posed no threat to this man. They know this guy waited an hour after he mangled her face to contact authorities. He opened the door, shot her, closed it, and chilled out while she bled out on his porch. As far as I've heard he was not tested for substances but she was. Authorities WERE LOOKING FOR AN EXCUSE NOT TO TAKE THIS TO TRIAL!!!! They found it.