Some efforts have been made to find Biblical support for the position that the Bible opposes capital punishment. One argument points to Genesis 4:15, noting that God spared Cain and did not execute him.

While true, what little indication we have here is that this was arguably a crime of passion (Gen. 4:8) or a scenario prior to the establishment of post-diluvian societal laws. More importantly, the mark of Cain was an act of God's profound mercy, granting him time for repentance rather than immediate death. This suggests that mercy and the opportunity for repentance remain paramount, even when a grave sin has been committed.

> Gen. 4:8-15 Now Cain said to his brother Abel, "Let's go out to the field." And while they were in the field, Cain attacked his brother Abel and killed him. Then the LORD said to Cain, "Where is your brother Abel?" "I don't know," he replied. "Am I my brother's keeper?" The LORD said, "What have you done? Listen! Your brother's blood cries out to me from the ground. Now you are under a curse and driven from the ground, which opened its mouth to receive your brother's blood from your hand. When you work the ground, it will no longer yield its crops for you. You will be a restless wanderer on the earth." Cain said to the LORD, "My punishment is more than I can bear. Today you are driving me from the land, and I will be hidden from your presence; I will be a restless wanderer on the earth, and whoever finds me will kill me." But the LORD said to him, "Not so ; if anyone kills Cain, he will suffer vengeance seven times over." Then the LORD put a mark on Cain so that no one who found him would kill him.

Some sometimes argue that God excused Cain, a murderer, with a nearly innocuous punishment.

1. This punishment was hardly innocuous, in a time when corporate survival was a key to living - in effect it was a slow death sentence.
2. At this stage in world history, had the cycle of vengeance been allowed to start, it would have quickly depopulated the world. This is not merely a matter of situational ethics for this was indeed a situation where one universal (general preservation of order on a "global" scale) had to prevail over another (the just punishment for a murder). "Situational ethics" should not be confused with a "hierarchy of morals."
3. Building a city may seem like a settled life versus being a restless wanderer. But since the ground would not produce food for Cain, what would he have to do in order to get food? He would have to wander around from place to place and find it -- building a city wasn't going to keep him eating. The words used here, however, would also describe well a criminal always on the run from justice.