The Torah tells us that a proven murderer must be put to death. His trial takes place in a special Rabbinical court (SANHEDRIN) where a death sentence was very rare. If the Sanhedrin put more than one person to death in 7 years the court itself was considered a "murderous court". Putting a person to death for the sin of murder was indeed a serious matter as we can see from the following list:

(1) For a conviction the Torah requires two kosher male witnesses that saw the murder with their own eyes. If they did not actually witness the murder, no other evidence will lead to a conviction.

(2) Even when there are two witnesses to the murder, they are required to warn the man before the murder, that if he kills he is liable to the death penalty. The man must respond to this warning in a way that makes it clear that he received it, and the murder must have followed immediately after the warning.

(3) The two witnesses that come to the Sanhedrin must answer certain inquiries properly and if one of the witnesses fails to answer properly or answers that he does not know the answer - the entire testimony is null and void. In addition, the members of the court may ask any other questions and if the two witnesses disagree in their answers the testimony is also null and void.

(4) All this can only happen when the Sanhedrin is in its proper place on the temple mount in Jerusalem. If the court meets elsewhere, it is not allowed to take on cases of capital punishment.