WHEN LIFE GENERATES DEATH (LEGALLY)
In religious Jewish communities, the ones derived from the Diaspora, there isn't a hierarchic structure that imposes moral choices to anyone; all ethnic groups have a head rabbi and the Jerusalem rabbi has maximum authority (however, he is a primus inter pares), but each rabbi is independent and his judgements are a point of reference for the community.
For orthodox Jews, Mosaic law of "a life for a life, an eye for an eye, a tooth for a tooth, a hand for a hand, a foot for a foot", codified in the 617 precepts of Leviticus and Deuteronomy, according to which death penalty is a lawful punishment, is still valid. The crimes which it punishes are murder, adultery, incest, omosexual intercourse, blasphemy, idolatry, violation of Saturday, divorce (only for women); methods to execute the sentence are stoning, stake, hanging to wood, stroke with sword, strangling and administering white-hot lead drops in sentenced's throat. Actually nowadays these rules are inapplicable in toto or for some crimes and in the traditional form of stoning, as they contrast with the law of the countries where Jews communities are; like in Israel, which is a lay State whose civiIian law is independent from religion, though there is death penalty for military crimes and genocide.
So, a Jews doesn't find reasons against death penalty in his religion, but only in his conscience.