This was a stude of Law Enforcement Officers killed by handguns. Some of this killings were with the officers gun. The first number is for the yr 2007', the second number in ( ) is the 10 yr number. So keeping with the OP post, in a 20 yr period we know that 20 officers were killed with .22 pistols. Looking at the other numbers clearly shows that the .22 is not the best choice, however it can do the job in a self defense situation.
<TABLE dir=ltr border=1 cellSpacing=0 cellPadding=7 width=661><TBODY><TR><TD height=18 vAlign=top colSpan=8 *********#f3f3f3>
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1988
</TD><TD height=9 vAlign=top width="12%">
371
</TD><TD height=9 vAlign=top width="12%">
251
</TD><TD height=9 vAlign=top width="12%">
752
</TD><TD height=9 vAlign=top width="12%">
3
</TD><TD height=9 vAlign=top width="12%">
2.4
</TD><TD height=9 vAlign=top width="12%">
540
</TD><TD height=9 vAlign=top width="13%">
100
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1989
</TD><TD height=9 vAlign=top width="12%">
450
</TD><TD height=9 vAlign=top width="12%">
329
</TD><TD height=9 vAlign=top width="12%">
1073
</TD><TD height=9 vAlign=top width="12%">
3.3
</TD><TD height=9 vAlign=top width="12%">
2.6
</TD><TD height=9 vAlign=top width="12%">
823
</TD><TD height=9 vAlign=top width="13%">
157
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1990
</TD><TD height=9 vAlign=top width="12%">
425
</TD><TD height=9 vAlign=top width="12%">
307
</TD><TD height=9 vAlign=top width="12%">
1176
</TD><TD height=9 vAlign=top width="12%">
3.8
</TD><TD height=9 vAlign=top width="12%">
2.8
</TD><TD height=9 vAlign=top width="12%">
965
</TD><TD height=9 vAlign=top width="13%">
220
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1991
</TD><TD height=9 vAlign=top width="12%">
440
</TD><TD height=9 vAlign=top width="12%">
332
</TD><TD height=9 vAlign=top width="12%">
1112
</TD><TD height=9 vAlign=top width="12%">
3.4
</TD><TD height=9 vAlign=top width="12%">
2.6
</TD><TD height=9 vAlign=top width="12%">
846
</TD><TD height=9 vAlign=top width="13%">
175
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1992
</TD><TD height=9 vAlign=top width="12%">
392
</TD><TD height=9 vAlign=top width="12%">
279
</TD><TD height=9 vAlign=top width="12%">
1094
</TD><TD height=9 vAlign=top width="12%">
3.9
</TD><TD height=9 vAlign=top width="12%">
2.7
</TD><TD height=9 vAlign=top width="12%">
875
</TD><TD height=9 vAlign=top width="13%">
193
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1993
</TD><TD height=9 vAlign=top width="12%">
415
</TD><TD height=9 vAlign=top width="12%">
312
</TD><TD height=9 vAlign=top width="12%">
1193
</TD><TD height=9 vAlign=top width="12%">
3.8
</TD><TD height=9 vAlign=top width="12%">
2.8
</TD><TD height=9 vAlign=top width="12%">
928
</TD><TD height=9 vAlign=top width="13%">
173
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1994
</TD><TD height=9 vAlign=top width="12%">
419
</TD><TD height=9 vAlign=top width="12%">
331
</TD><TD height=9 vAlign=top width="12%">
1146
</TD><TD height=9 vAlign=top width="12%">
3.5
</TD><TD height=9 vAlign=top width="12%">
2.6
</TD><TD height=9 vAlign=top width="12%">
689
</TD><TD height=9 vAlign=top width="13%">
138
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1995
</TD><TD height=9 vAlign=top width="12%">
435
</TD><TD height=9 vAlign=top width="12%">
345
</TD><TD height=9 vAlign=top width="12%">
1728
</TD><TD height=9 vAlign=top width="12%">
5
</TD><TD height=9 vAlign=top width="12%">
3.6
</TD><TD height=9 vAlign=top width="12%">
1245
</TD><TD height=9 vAlign=top width="13%">
255
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1996
</TD><TD height=9 vAlign=top width="12%">
410
</TD><TD height=9 vAlign=top width="12%">
318
</TD><TD height=9 vAlign=top width="12%">
1292
</TD><TD height=9 vAlign=top width="12%">
4.1
</TD><TD height=9 vAlign=top width="12%">
3.1
</TD><TD height=9 vAlign=top width="12%">
892
</TD><TD height=9 vAlign=top width="13%">
201
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1997
</TD><TD height=9 vAlign=top width="12%">
329
</TD><TD height=9 vAlign=top width="12%">
253
</TD><TD height=9 vAlign=top width="12%">
1040
</TD><TD height=9 vAlign=top width="12%">
4.1
</TD><TD height=9 vAlign=top width="12%">
3.1
</TD><TD height=9 vAlign=top width="12%">
708
</TD><TD height=9 vAlign=top width="13%">
121
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1998
</TD><TD height=9 vAlign=top width="12%">
321
</TD><TD height=9 vAlign=top width="12%">
249
</TD><TD height=9 vAlign=top width="12%">
856
</TD><TD height=9 vAlign=top width="12%">
3.4
</TD><TD height=9 vAlign=top width="12%">
2.6
</TD><TD height=9 vAlign=top width="12%">
529
</TD><TD height=9 vAlign=top width="13%">
302
</TD></TR><TR><TD height=9 vAlign=top width="12%">
1999
</TD><TD height=9 vAlign=top width="12%">
202
</TD><TD height=9 vAlign=top width="12%">
155
</TD><TD height=9 vAlign=top width="12%">
621
</TD><TD height=9 vAlign=top width="12%">
4.0
</TD><TD height=9 vAlign=top width="12%">
3.2
</TD><TD height=9 vAlign=top width="12%">
389
</TD><TD height=9 vAlign=top width="13%">
88
</TD></TR><TR><TD height=9 vAlign=top width="12%">
2000
</TD><TD height=9 vAlign=top width="12%">
134
</TD><TD height=9 vAlign=top width="12%">
129
</TD><TD height=9 vAlign=top width="12%">
471
</TD><TD height=9 vAlign=top width="12%">
4.6
</TD><TD height=9 vAlign=top width="12%">
3.3
</TD><TD height=9 vAlign=top width="12%">
367
</TD><TD height=9 vAlign=top width="13%">
58
</TD></TR><TR><TD height=9 vAlign=top width="12%">
2001†
</TD><TD height=9 vAlign=top width="12%">
67
</TD><TD height=9 vAlign=top width="12%">
67
</TD><TD height=9 vAlign=top width="12%">
162
</TD><TD height=9 vAlign=top width="12%">
3.6
</TD><TD height=9 vAlign=top width="12%">
2.7
</TD><TD height=9 vAlign=top width="12%">
103
</TD><TD height=9 vAlign=top width="13%">
22
</TD></TR><TR><TD height=10 vAlign=top width="12%" *********#e0e0e0>
TOTALS
</TD><TD height=10 vAlign=top width="12%" *********#e0e0e0>
4810
</TD><TD height=10 vAlign=top width="12%" *********#e0e0e0>
3657
</TD><TD height=10 vAlign=top width="12%" *********#e0e0e0>
13716
</TD><TD height=10 vAlign=top width="12%" *********#e0e0e0>
3.82
</TD><TD height=10 vAlign=top width="12%" *********#e0e0e0>
2.86
</TD><TD height=10 vAlign=top width="12%" *********#e0e0e0>
9899
</TD><TD height=10 vAlign=top width="13%" *********#e0e0e0>
2203
</TD></TR></TBODY></TABLE>
So again coming down to training, and I am assuming LEO's for the most part get better training than MOST civilian self defense minded home firearm owners. Of 9,899 LEO shots fired only " 2203" hit the target.
So in conclusion .44 mag, .45, 40, .357 or .22, if you miss during a stressful fight for your life, it is not going to matter what caliber. So practice a lot. If the .22 is all someone has to defend with, practice some more!!!