Googled keywords: Handgun, penetrating power, stopping power, exit wound, effective range
I have a standoff situation in the living room of a standard house. Jill is being held tightly by Jack, who is standing behind Jill with a gun to her temple. Jack's attention is completely on something in front of him. Unfortunately for Jack, this puts his back to an open window. Robin plans to shoot Jack through this window. The problem is that Jack is plastered against Jill. What are the chances that a bullet will go through and kill both Jack and Jill? Robin has a .45 handgun, is a good shot, and stands about 30 ft away.
My google-fu says that most handgun shots produce exit wounds, which would naturally mean hitting Jill, but I don't know if she would get seriously injured. Could Robin aim for the skull and assume that the extra bone would stop the bullet but still kill Jack?
An alternative situation is if Jack is standing close to Jill but not touching her. How far apart would they have to be before the exiting bullet is A) too weak to hurt Jill, or B) has a good chance of missing her? I know that in movies people don't get shot through someone else by accident, but in movies exit wounds aren't common either :)
Apologies if the answer is obvious; I know nothing about guns except what Google spat out in the last hour or so...