When you're at the range, and you line up your shot to center mass, and you pull the trigger, where you miss is indicative of what you're doing wrong -- if it's consistent. (Some short barrel concealed carry guns are not accurate at longer ranges; they aren't intended to be, either. However, the average full size hand gun is intended to be pretty accurate.)
Here's a link to a helpful free (PDF) target that may make you a better shot.
If I miss at the range -- which is rare -- I usually miss down and to the left of the bullseye (but not by much) because I'm pulling my index finger a little too hard -- I'm tightening my fingers.
If I was in a high stress situation -- say one where a yelling, large, aggressive nearly 300 pound man is charging me, I'd probably tighten up even more and miss to the left, say, hitting the assailant in the right arm. As I continued to pull the trigger, I would likely start missing up from the recoil of the gun -- more likely if I've firing a
.40 cal, which has a sharper, more upward recoil than a
.45 ACP or a 9mm does. (I've shot a few
.40 cals before -- I've not shot a
.40 cal Sig Sauer, but I have shot a couple of Berettas and I wasn't a fan. Besides --
.45 ACP is better than
In this regard, the autopsy result of Michael Brown tends to support the officer's account of what happened. Brown was charging him, and under stress he over tightened, and missed to his left from center mass which would be the assailant's right arm / shoulder as he likely did not take a lot, if any, time to re-sight as he was in the line of a charging bull.
The other piece of evidence is going to be the brass. If it's all in a localized area, the officer was standing still. If it's scattered, then he was running toward the assailant.
The other question, which leads into another somewhat related point: How many rounds did Officer Darren Wilson fire? His gun had a 12 round magazine (+1 in the pipe) so it's possible that he missed a few times - which wouldn't surprise me, as here's a dirty little secret:
The police do not train with their firearms enough, or even as much as the average CHL holder.
A couple of my closest friends are police officers, and I can out shoot them any day of the week and twice on Sunday. Despite their "training" I have a much tighter grouping and many, many more bulls-eyes with the same weapon than they do.
The reality is, this trend tends to hold across the general population. You are far more likely to get shot by a cop -- whether intentional or not -- than you are a legal concealed carry licensee.
Consider that little fact the next time you want to think that "only the police should have guns".
And if you are a concealed license holder -- when was the last time you practiced? Find a range and keep those skills sharp.