I would add just a word of caution here for those FReepers who are unfamiliar with the topic of Judaism and capital punishment, who might take this statement as teaching that Judaism does not really inflict capital punishment at all. It is true that the carrying out of death sentences must be carried out according to the Oral Law and that this does indeed set severe boundaries. For one thing, the person must have previously been formally warned before two witnesses (I think the number is two) that he is engaged in an activity that is punishable by death. If this warning has not been given, the person cannot be put to death by the court. Also, there must be at least two witnesses to the exact same overt act. Two witness, each of whom witnessed a different act, are not sufficient. Neither is confession by the person himself admissible, or hearsay, or circumstantial evidence (though the King of Israel has the authority to order one executed based on circumstantial evidence). Also, as I understand it, people not mentally competent may not be put to death.
Now it is true that with all these requirements in place that capital punishment under the Torah is indeed rarer than might be at first assumed by a mere reading of the Written Torah itself (the Talmud noted that a court that inflicted the death penalty once in seventy years was considered brutal). However, it must be stressed that if anyone met all these criteria he had to be put to death by the court. In fact, the Torah specifically forbids having mercy on someone who has met all the criteria for being put to death.
Also, even in those cases where someone has committed a capital crime but has not met the criteria which would allow the death sentence by the court, HaShem Himself reserves the right to inflict the penalty. I have read that, for example, someone guilty of a crime punishable by death by strangulation, but who cannot be punished by the court, may choke to death while eating. It requires a total trust in G-d to obey Him even when He forbids the human court to take action for some technical reason when the person has done something worthy of death. The lack of this type of faith shows just far yeridat hador (the regression of humanity through the generations) has come.
Finally, the laws for Benei Noach (non-Jews) are somewhat different. While confessions and circumstantial evidence are still not admissible, no prior warning is required and only one witness is necessary. Also, as I understand it, a non-Jew is responsible for obeying the Noachide laws even if he is ignorant of them. So the fact that the current state of Israel does not have the authority under the Torah to enact the death penalty (and that Torah Jews must not allow it to do this) does not mean that Torah requires a crusade against the death penalty among non-Jews. However, our current legal system is not that commanded by HaShem, and only one form of capital punishment--death by beheading--is permitted to non-Jews. It is imperative for Jews and non-Jews to educate themselves and fight for obedience to G-d in our laws and systems of justice, and this includes not only the fight to maintain capital punishment but also to see to it that it is carried out only in accordance with Divine instructions. I am afraid we are a long way from there yet.