life in prison vs. death penalty

I got into a little debate one day with a friend of mine about the death penalty. Now im not completly against the idea of killing a murderer or a rapist. There is the single biggest problem of not killing the wrong person. This is so obvious that Im not even going to discuss that part. The next point I brought up was one that we are all interested in, the cost. I told him that it cost more to kill a criminal than to put them in jail. He said that it can't because of how expensive it is to keep someone in jail. Now we were having this debate in a bar and couldn't exactly prove it either way. Now I can see the logic behind assuming that it is more expensive to keep someone in jail for 50 years than to stick a little poison in his(or her) arm. So I looked into it real quick and of course theres at least one entire website dedicated to the costs of the death penalty. But for greater clout I am going to use the information from Amensty International, actualy much of it is the same info. According to these sites it is about 70% more expensive to kill a person than to put them in jail for the rest of there lives. Maybe there are places that claim something different, but I didnt have time to do a lot of reasearch. I think my friend was only assuming anyway. have a good one, Im goin to lunch.