Is it permissible to pray behind a liar, a transgressor (fasiq), a profligate (fajir), a smoker, or an innovator (mubtadi'), especially if he is knowledgeable in the jurisprudence of imamate?

Scholars have differed regarding the validity of prayer behind a transgressor (fasiq). Malik and Ahmad, in one of the narrations, held that it is not valid, whereas Abu Hanifa and Al-Shafi'i, and the other narration from them, held that it is valid. The validity of prayer behind a transgressor is indicated by the actions of the Companions, such as Ibn Umar, who prayed behind Al-Hajjaj, and by the statement of Al-Tahawi: "We deem prayer valid behind every righteous person and every transgressor from the Ummah of Muhammad (peace be upon him)."