The Qur'an does not recommend the death penalty in all cases of murder. Look at the Qur'anic verse which deals with the death penalty, 'O ye who believe! The law of equality is prescribed to you in cases of murder : the free for the free, the slave for the slave, the woman for the woman. But if any remission is made by the brother of the slain, then grant any reasonable demand, and compensate him with handsome gratitude. This is a concession and a mercy from your Lord.' (Qur'an 2:178)
It is the close relatives of the murdered person who are to decide whether the murderer is to be saved from death or not. If it is agreeable for them, they can allow him to go free after taking the required blood-money (Diya). The court has no right whatsoever to oppose them if the relatives decide to let him go free. The blood-money for murder is a hundred camels. If this has been taken and the murderer is let off then from that moment on there can be no retaliatory action against him.
In short, therefore, if the relatives of the murdered person are so willing, they can accept the blood-money and let the muderer go free. They can then use the blood-money to rehabilitate the family which has now been orphaned and to make a means of livelihood for them as well. The Qur'an, which gave the final authority to decide the fate of the murderer to the relatives of the murdered person, here shows its brightest and most humane face of all.