Apostasy in Islam is defined/described as follows:
Irtidad and Ridda [signifies 'turning back' from Islam to another religion or to unbelief] are the technical Arabic terms and an apostate is a murtadd; (Lit. "one who turns the back") [forsakes Islam for another religion or unbelief]. In the Qur'an, God's punishment for Irtidad is only in the afterlife [life in the next world] (Sura 16:106, ff.; 3:86 ff.; 2:217), although one who repents, not having become confirmed in apostasy, will be saved.
In the Prophetic Tradition, apostasy is punishable by death, a view which is upheld and detailed in both the Sunnite and Shi'ite law books.(4) However, the offender is usually granted an opportunity to recant. Only adult, sane, male apostates who have acted freely are to be executed (traditionally by the sword). Women are either imprisoned until they recant (Hannafites and Shi'ites) or are executed (Malikites, Shafi'ites, and Hanbalites).
The death penalty is rarely carried out today, but there remains a powerful sense of outrage among Muslims when one of their number forsakes the community.
Bibliography, Muhammad Ali, The
Religion of Islam (nd), pg. 591-99; S.M. Zwemer, The Law of Apostasy
in Islam (1924); Burhan al-Din Ali, The Hedaya, etc., Hamilton,
(1791), II, 227. (F.M. Denny)."
3. Keith Crim, General Editor, Abingdon Dictionary of Living Religions, Nashville, USA 1981
4. The Hanafi school of law is based upon a Prophetic Tradition (Hadith) reported by 'Atiyah ibn Qais al-Kilaby (vide Sarakhsy, Sharha al-Siar al-Kabir, vol IV, 108). The Hanafi scholars rely on this Tradition: "The Prophet has said: 'Whoever commits murder or fornication or theft [in our territory] and escapes and then returns with permission, shall be tried and punished for what he wanted to escape from. Yet if he has committed murder, or fornication or theft in the territory of the enemy and came with permission, he will not be tried for what he committed in enemy territory." However, as to the enforcement of the law, the Sunnite and the Shi'ite schools of law operate on two different principles: the Sunnites exercise their enforcing authority/powers within the legal/geographical boundaries of their own jurisdiction. But under the Shi'ite law, enforcement powers can be exercised even in foreign lands, that is to say, beyond the jurisdiction of their own country. In other words, the Sunnites do not believe in extraterritorial jurisdiction, but the Shi'ites do.
As to the enforcement of punishment of an apostate and the pre-prosecution, pre-trial, and pre-conviction procedures, see the excerpt of paragraph 332 under the next heading of 'The Muslim Conduct of State' and Kitab al-Fiqh ala al-Madahib al-Arbaa'h