(1) "Murtad Fitri" means a person who is born of a Muslim parent and then he rejects Islam. "Fitrah" means creation. The term "murtad fitri" implies that the person has apostate from the faith in which he was born.

(2) "Murtad Milli" means a person who converted to Islam and then later on he rejects Islam. Milli is from millat which means religion. The term "murtad milli" implies that the person has apostated from his religion and the Muslim community.

In the first case, the apostasy is like the treason against God; whereas in the second case, the apostasy is like the treason against the Muslim community. Probably, that is why the Sh`iah jurisprudence deals with these two kinds of murtads differently:

• A former kāfir who became a Muslim and then apostates (murtad milli), he is given a second chance: if he repents, then he is not to be killed; but if he does not repent, then he is to be killed.

• But one who is born as a Muslim and then apostates (murtad fitri), he is to be killed even if he repents. It is important to understand that in case a murtad fitri repents, Allāh may accept his repentance and he may be forgiven in the hereafter, but he still has to go through the punishment prescribed for his treason in this world.

This punishment is only applicable in case of apostasy by men; in case of women, the punishment is not death but life imprisonment. And if such a woman repents, then her repentance is accepted and the punishment is lifted.

In writings of some of the Sh`iah jurists, one gets the sense that the punishment of murtad is to be implemented only in dāru 'l-Islām (i.e., the Muslim world), and that if the murtad flees to dāru 'l-kufr (i.e., the abode of kufr), then he is not to be pursued.

Source: Here!