Anyone who says that a .22 won't penetrate is completely oblivious of actual facts and is likely falling into the extremely dangerous fallacy of equating performance and ability with size. Far too many people look at the .22 and see just a cute little round that just OBVIOUSLY can't be dangerous because it's far too tiny and cute compared to larger rounds.
A .22 caliber bullet, after hitting a door frame and deforming significantly, penetrated deeply into Ronald Reagan's chest and almost killed him.
An individual I worked with years ago was shot accidentally by a friend at less than 10 feet with a .22 semi-auto pistol.
The bullet hit him in the right chest, broke a rib, traversed the chest cavity bounced off a rib in the left chest, and ended up in his left kidney. In total, probably close to 15 inches of penetration and a wound that shouldn't have been survivable, and almost wasn't.
To those who doubt that ballistic gelatin is a valid testing media. The reason it was chosen as a testing media is because it approximates the average mean density of all human tissue in the body. That's why bone isn't cast into testing gelatin - it would throw off the average mean density figures.
What's seen in ballistic gelatin testing by FBI and the industry (which has largely adopted it as their testing media, as well) has been, to a large degree, born out by what is actually seen in the same bullets fired into living humans.
Dr. Martin Fackler of the Firearms Tactical Institute has written extensively on this subject.
Many of Dr. Fackler's articles and studies are available for free.
http://www.firearmstactical.com/
At the risk of becoming persona non grata, I would go so far as to say that anyone who isn't familiar with this literature should probably avoid posting. Contrary to what you may read on the internet, many of the top experts (as in "expert witnesses" and peer-reviewed scientists) have developed an extensive body of research on these topics.
I am not an expert by any means, but I know several people who would qualify as "experts," in the sense of having withstood peer review. All of these people tend to support Dr. Fackler's findings.
If anyone really cares, I can elaborate at some length.