I think a lot of the controversy over the Marshall / Sanow study is due to people mis-interpreting the intent of the study. There are a lot of factors that can lead to success or failure in a gunfight: Training, firearm type and reliabiliuty, caliber, ammunition type, number of adversaries, number of allies, etc.
The M / S study is an attept to isolate one factor, ammunition performance, from all the others. Thus, once you have selected the firearm that works best for you, and trained endlessly with it, you can look at the results of the M/S study and select one of the better (if not the best) ammunition types for that firearm.
The problem with including multiple hits or stops/encounter is that then you start to look at factors other than ammunition performance. Which is great, if that's what you want to do, but that was not the purpose of the M/S study.
Say, for example that you have a guy who was shot 37 times with a 9mm. Was he shot 37 times because the first 36 didn't stop him, or were the police just overly trigger happy? Or say you have a 6 shot stop with a 9mm vs a 3 shot stop with a .45. Does that mean that the .45 is more effective, or were both guys DRT after the first shot, and the 9mm's faster cyclic rate just allowed more additional shots before gravity took over?
There's just too many other variables in multiple hit encounters. If you are looking solely at ammunition performance, the best way to eliminate those other variables is... guess what... look only at one shot stops.
There is no magic bullet. Marshall himself says "Shot placement. Shot placement. Shot placement." But, given identical shot placement, the one with the better performing ammunition will have a slight edge. And that's the point of the study.
