You're preaching to the choir here in terms of questioning a number of things with MPD. But to me, BB's physical presence isn't one of them. He was on the phone constantly with different people while his friend drove, so they would have immediately gotten cell tower data to show his movement. Plus the testimony of the friend who was driving the car with MS plates.
I'd rather question things like, why clear the scene in record time? Why point us toward an Altima nearby at 2 am when there was a dark SUV leaving the church at 4:30 that they never told us about and still haven't? Why go from a 6'0" perp to one that is 5'7" to 5'9", to a forensic video reconstruction where they say things are much clearer now but we aren't going to release details, to never mind, we are going to tell you, he's 5'2" to 5'7", and maybe not a he. And even though we announce that height range and tell the public not to bother tipping POIs outside that range, we're going to go execute a SW on a guy who is much taller than 5'7".
And then they tell us that someday when an arrest is made, they'll open the books up and we will be able to see that they did things the right way, but in the meantime to withhold judgment on their investigation.
So I certainly get what you're saying. But not in terms of BB's whereabouts. Even if MPD dropped the ball, remember there was a 4-day presentation of the case this summer in Austin to other agencies. I think those agencies would have poked holes in BB's alibi if there were holes to poke.