Arguments For Capital Punishment

Common reasons in support of capital punishment
bullet The Bible The Bible requires the death penalty for a wide variety of crimes, including sex before marriage, adultery, homosexual behavior, doing work on Saturday and murder. It even calls for some criminals (e.g. prostitutes who are the daughters of priests) to be tortured to death by being burned alive. Most Christians, with the exception of those in the Reconstructionist movement, feel that many of these grounds for the death penalty no longer apply to Christian societies. U.S. However, Bible passages are still used to promote the retention of capital punishment for murderers; some advocate that homosexuals also be executed.
bullet Justice/Vengeance Many people feel that killing convicted murderers will satisfy their need for justice and/or vengeance. They feel that certain crimes are so heinous that executing the criminal is the only reasonable response.
bullet Deterrence Many people feel that the death penalty will deter criminals from killing. This does not seem to be confirmed by an analysis of the available data. However, it feels intuitively correct for many people. 1 to 6
bullet Value of human life: "It is by exacting the highest penalty for the taking of human life that we affirm the highest value of human life." (Edward Koch).
bullet Cost: Once a convicted murder is executed and buried, there are no further maintenance costs to the state. This appears to be invalid; the cost to the state paying for multiple appeals is greater than the cost of imprisoning an inmate.
bullet Public safety: Once a convicted murderer is executed, there is no chance that he will break out of jail and kill or injure someone.

http://www.religioustolerance.org/executb.htm