)
There are close to 30 sins which carry a death penalty in principle. These include committing murder, adultery, or incest, desecrating the Sabbath publicly, and kidnapping and selling a person into slavery. A court composed of 23 ordained judges had the authority to put someone to death. (The ordination required here was the original ordination granted by teacher to student in an unbroken chain that began with Moses.)
However, in contrast to other nations and religions of ancient times, it was very rare for the Jews to actually put anyone to death. In fact, one of the Sages asserted that a Sanhedrin that executed one person in seven years was considered to have deviated from the accepted norm and was called “brutal.” Another Sage maintained that a court that executed even one person in 70 years was considered brutal. This is because the terms and conditions the halakha establishes for capital punishment are so restrictive that they are very difficult to meet. One of these conditions is there must be witnesses who explicitly told the perpetrator before sinning that the punishment is death if he commits this sin. Furthermore, it must be clear the sinner understood the warning and did it anyway. With the exception of people with severe anger management problems, no one would do such a thing. We see the Torah’s death penalty is not meant to be put into practice. Rather, it is meant to achieve two things: 1) to make the gravity of the sins clear, and 2) to establish communal norms so no one would dare to commit these sins publicly.
In practice, on the rare occasion the death penalty was meted out, it was primarily to murderers. But before the destruction of the Second Temple, when the Jews were under Roman rule, society's moral levels declined, and murder abounded. The Sages saw the death penalty was no longer serving as a deterrent. If the courts had put Torah law into practice, they would have had to execute more than one person in seven years. It was decided the Sanhedrin would exile itself from its proper location near the Temple and move to a nearby street. This move meant the courts throughout the land no longer had the authority to adjudicate death penalty cases. Since the goal of punishment is deterrence (and the accompanying preservation of human lives), there was no reason to continue imposing it if it was not effective. We learn from this that the High Court had the authority whether or not to impose capital punishment depending on the circumstances; by moving, the Sanhedrin had effectively repealed the death penalty.
