There's already a discussion of Cheney's Negligent Discharge over at Krupa's blog. Rather than totally hijack his comments, I wanted to link to Summers v. Tice for those not in the legal community. Those in law school probably immediately thought of this seminal torts case involving a quail hunting accident, but for everyone else, it is short as far as cases go, and reading it might even be fun.

Overall, yes, you can be civilly liable for a Negligent Discharge while hunting, and no, the fact that Whittington didn't announce his return does NOT change Cheney's moral or legal liability whatsoever. Every time you discharge a firearm, you are responsible for the terminal resting place of each and every projectile. When in doubt, especially when hunting a 6oz game bird, do not shoot.