Purity: Barriers Between the Prayer Performer and the Corpse

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 590:

There must not be a curtain, wall, or a similar thing between the corpse and the person performing the prayer. However, there is no problem if the corpse is in a coffin or something similar.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)