Prayer: Can I Pray Behind an Unknown Imam?

Practical Laws of Islam as per the teachings of Imam Khamenei

Prayer: Can I Pray Behind an Unknown Imam?

English:

Question #557:

Is one allowed to start to pray behind a congregational prayer imam about whom one has no information and does not know?

Answer #557:

If he knows — through any shar‘ī means — that the Imam is ‘ādil, it is permissible to pray behind him and the congregational prayer is correct.

-Imam Khamenei, Practical Laws of Islam, Importance and Conditions of Prayer