Marshall and Sannow's works are best used for fire starter or to perhaps level out a table on a very uneven surface, it is pretty well useless for anything else. Terminal ballistics is the science of how bullets do damage and stop, or fail to stop, attacks, and effects of bullets in various conditions and scenarios are far more useful to us than poorly cobbled together rough statistics. And worthless, poorly defined statistics is Marshall and Sannow's work. With all of their thrown together numbers, we don't get useful context to determine the effectiveness of the round in those scenarios, and the individual incidents are too different to be put together in a similar category in the first place for statistical purposes. M&S don't distinguish between a shot through intestinal track, a shot through the aorta, though the kidney, straight through from the front of the torso, a long angle shot through the torso that failed to get to organs, ect. Every single event they record for first shot to the torso is sloppily, carelessly lumped with each other, the only thing separating the shoots is cartridge load!
If you took M&S's trash and tried to replicate their percentages of one stop shot in real life scenarios, the relevance is non existent. They didn't put together a couple of anecdotes, they threw together cherry picked numbers to create the message they wanted, and even if they did do it right, the information is still too poorly separated scientifically to actually draw a single scientific conclusion. This mass aggregate without proper definition is pointless. Keep in mind, science is cause and effect, correlation is observation to hypothesis, not proof of anything. M&S's work do not, in any way, actually make any scientific or valuable statements to prove any of their theories, ideas, or actually prove any round is better than any other.
I believe Dr. Fackler wrote a very good article about why Marshall and Sannow are complete garbage, and shows why the work is less than relevant, it is misleading.
As for the original subject, I'll plug my own video shamelessly to make a point:
[ame]https://www.youtube.com/watch?v=JQcNjIThmHQ[/ame]
Attackers may not line themselves up in perfect straight angles to you, may not be standing straight up and walking tall at you, or standing still. You may not be standing in your proper shooting stance like you would be at the range or during normal training. Between your stance and the attacker's stance, shot angle can multiply the depth of shot to vitals dramatically, turning a 5 inch shot to a man's heart into a 18 inch shot. As far as pure depth in the human body, 18 inches or even further, especially as an attacker's size is increased in our theory, becomes very real indeed.
Yes, different tissues resist differently. From the old FBI and other works I've seen human skin can range from 2 to 4 inches worth of average muscle or ballistics gel because of its strength and elasticity. A steel pellet that pierces 3 inches into a ballistics gel block may not even pierce someone's skin in a certain situation, meaning that just because something can pierce a block does not necessarily mean it will pierce flesh, or certainly won't pierce that much in a living being. This means that 12 inches in a gel block can easily be less than what we think.
As for peace officer vs. citizen, I think that argument is almost null. Just because police are more likely to get into a gun fight, and can get into more severe gun fights, have to chase after bad guys, ect., does not mean that the realities of a gun fight are different. If a civilian is in a gun fight, it will be no different than if he was a cop, and all the real world laws and physics apply. If your attacker is at an angle and you are shooting at an angle, that doesn't magically change the terminal ballistics and effects of your bullet because you aren't a police officer. A gunfight doesn't get any easier, and the bad guys don't shoot any different, or act any different, because you are a civilian. The same failures a bullet may have for a police officer can very easily happen to a non police officer. Bad guys don't make exceptions, and don't follow magical rules about killing innocent people.