Legal concealed carry saves more innocent lives than it takes.
In Texas the detailed statistics are compiled annually by the Department of Public Safety and published on the internet. It is likely that the Texas experience with Concealed Handgun Licenses would be about the same in other states. The last year for which statistics are published is 2011 for convictions. http://www.txdps.state.tx.us/rsd/chl/index.htm
In 2011 there were 512,625 people who had CHLs. Out of those people there were exactly four (4) murder convictions. Out of the general population there were 553 convictions for murder in its various forms.
So very, very few CHL holders go bad, but some do.
The DPS also publishes an annual Crime in Texas Report. http://www.dps.texas.gov/crimereports/10/citCh3.pdf
From that report, page 15:
Statistics on murder circumstances, victims, and
victim/offender relationships on the next page
include justifiable homicides. Justifiable homicide
is the killing of a felon by a peace officer in the
line of duty or the killing (during the commission
of a felony) of a felon by a private citizen. In
2010, there were 98 justifiable homicides, of
which, 50 were felons killed by private citizens,
and 48 were felons killed by police.
In Texas all homicides, even those that are clearly self-defense, have to go before a grand jury which will rule if the killing was justified or not. So those 50 justified private citizen homicides were ones in which the defender genuinely and legitimately feared for his life. Since most shootings are merely woundings there would be a much larger number of justified woundings in which the defender genuinely feared for his life, but that number is not kept. Obviously there are dozens of cases each year in which a CHL holder uses their gun to save themselves.
Dozens of innocent lives saved versus four innocents killed shows the concealed carry is working in Texas. As already stated, there is no reason to believe that other CCW states have a different experience.
Legal concealed carry saves innocent lives.