A few comments in no particular order.
1) The error I see in some of the discussion above is that people are mistaking correlation for causation. Alternatively some folks are ignoring that correlation because it cannot be shown to be causative, while overlooking the reality that, statistically, about half of all "stops" that occur are not due to physical incapacitation.
2) Half is still a really big fraction, one that tells you that half the time a self defense shoot occurs, it really doesn't matter what handgun cartridge or load you are using.
3) That's on top of defensive gun uses where the gun isn't even fired. The percentage of defensive gun uses where the gun isn't even fired is estimated to be in the 90%-93% range.
4) The vast majority of armed citizens who conceal carry never draw a gun. I've relied on a gun three times in 34 years, but two of those were work related, both in situations where and armed citizen wouldn't be in the first place. Neither resulted in shots fired. The third was an attempted mugging at knife point that ended when I turned, noticed the attacker in the final stages of his approach, and reached for my handgun. The combination of no longer having the element of surprise and seeing me begin to draw a concealed handgun deterred the attack.
5) Putting this all together, handing cartridge choice matters in:
a) that very rare instance when an armed citizen actually needs to rely on a handgun for defensive purposes; AND
b) in just 7% to 10% of those rare events when a defensive handgun actually has to be fired; AND
c) in just half of the instances when the handgun is fired in just 7% to 10% of those very rare instances where it is needed at all.
6) More to the point, handgun cartridge choice does not matter in:
a) 90% to 93% of the instances when a handgun is used for self defense purposes (where it is never fired); and
b) in about half of the 7% to 10% of the defensive uses (where it is fired) any cartridge will stop the assault due to a psychological stop (for whatever reason).
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I book marked this several years ago. It addresses some of the short falls of the Marshall and Sanow data and he makes some good points without overstating the case.
An Alternate Look at Handgun Stopping Power | Buckeye Firearms Association
I'll argue, based on the data, that having a handgun on your person is far more important than having a handgun in one of the more popular rounds that are believed to be more likely to stop an attack. I'd much rather have someone carry a gun they will carry all the time, than have a larger handgun they don't carry all the time. I'd also much prefer someone have a handgun in a smaller caliber that they not only are willing to carry all the time but also shoot well, rather than carrying a small handgun that they are willing to carry all the time, in a larger cartridge that they do not shoot well. In that small percentage of defensive gun uses where the handgun is fired, whether it's a physical incapacitation or a psychological stop, it's the hits that matter.
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As an aside, my bachelors degree was in Criminology with a double major in Psychology and my masters degrees are in Mental Health Counseling and Vocational Rehabilitation counseling.
Based on my experience, it's common to have a group of academics, professors, or experts in a room who cannot decide on a basic definition. It's also common to have academics or professors or experts who choose to isolate themselves and pretty much ignore anything that does not conform to their personal beliefs. You'll see that in politics as well.
Worse, you'll also see it in the courtroom when the prosecution or the defense goes shopping for an "expert" witness who will give the desired opinion and/or worse, overstate what the evidence actually indicates or the degree of certainty involved. The FBI is currently standing with both feet in a steaming pile of excrement with evidence of FBI hair analysis experts doing exactly that - and training local experts to do the same thing. The number of unjust convictions based on that tainted testimony is enormous and some of them have been executed. That will have negative impacts on expert testimony for years.
Take "experts" with a large grain of salt and apply your own critical thinking, observation and logic to what they say.