Deliberate killing is a major sin, if the killer is a sane adult fulfilling 3 murder conditions he should be subjected to retribution of death as Qisas unless the victim's family forgives or accepts indemnity.
Deliberate killing, or murder
This refers to a case when the killer intends to unlawfully kill another human being, using means that will most probably lead to that person’s death. Three conditions must apply to make the killing a murder:
1) The killer’s intention is to kill his victim.
2) Knowledge that the person he intends to kill is a human being who enjoys the right to life.
3) The means used is something that normally leads to killing, whether it has a sharp blade or not.
Alternatively, the killing may be by using something or a method leading to death, such as poisoning or strangulation.
Ruling:
Murder has two rulings, the first of which relates to the hereafter, the other relating to this life. Islam considers murder a cardinal sin incurring severe punishment in the life to come, unless the murderer repents and mends his ways, earning Allah’s forgiveness.
:Allah says
‘He who deliberately kills a believer, his punishment is hell, therein to abide permanently. Allah will be angry with him, and will reject him, and will prepare for him a dreadful suffering.’
(4:93)
In this life, murder is punishable by death as a qisas, or equal punishment, unless the victim’s immediate family pardon the killer. This means that the immediate family have the options of enforcing the death punishment on the killer, or to give him a free pardon, or demand indemnity, or to agree a higher sum.
:This is based on a hadith that quotes the Prophet (peace be upon him) as saying
‘Whoever commits a murder is given to the victim’s immediate family. They may enforce the death penalty, or may take indemnity which is thirty camels over three years of age, and thirty over five years and forty pregnant she-camels. Whatever they agree above that is theirs to take.’
Related by Ibn Majah, hadith No. 2,626.
Islam encourages its followers to forego their rights whenever possible. Therefore, giving a pardon in such cases is encouraged as it demonstrates a God-fearing attitude.