Lobster is best kept alive until just before you are ready to cook it. A lobster that has been killed ahead of time can spoil and/or the meat will be tough. For most, the idea of killing anything is unpleasant. I try to cause the lobster the least amount of trauma. Because the lobster is a cold-blooded animal, its body temperature (as I learned in my ninth-grade biology class), adjusts to that of its surroundings. Having observed that a lobster is less active when cold than when warm, I find that if I place a lobster in the freezer 30 to 60 minutes before I am ready to cook it, the lobster becomes very relaxed and sleepy. In this state, the lobster doesn’t react to the boiling water, steam, or knife blade as much as when at room temperature. I don’t know if this is more humane, but it makes me feel better.