Is Salaat performed behind a zindeeq valid?

Answer

If it is known that a man is a zindeeq, then Salaat behind him will not be valid. A zindeeq is not a Muslim. When a Muslim misinterprets the Qur'aan, Hadith or any law of the Shariah and presents it in conflict with the Ijma' of the Ummah, then such a miscreant is termed a zindeeq. Zindeeq is a kaafir, hence Salaat behind him is not valid. Those who justify music, intermingling of sexes, television and other absolutely haraam acts are zindeeqs.