"I'd love to do [Activity X] but I just don't have the time." (maybe this one could be dealt with by torture rather than murder since it would wipe out most of the world's population in one fell swoop. Perhaps reading this post will do?)
This may need a little explanation since I have such a hard time convincing people. People who claim this usually admit after interrogation that they sometimes go to a movie or dinner with friends or whatever. So they could do activity X instead of those things! Ah! But socialising is better (more important than, whatever) than activity X. Fine, but that just means you prefer other stuff, not that you don't have time.
Even having a job doesn't excuse you, you could always quit.