Can you commit a mortal sin if you don't believe in God?

Mortal Sin
My bible study instructor says we cannot commit a mortal sin if you don’t have a relationship with God.
Please clarify for me, I am confused.
Peggy H

This link should explain the Roman Catholic Church’s teachings on mortal and venial sins. If you have any further questions or concerns that are not answered by these links, please contact Catholic Answers directly.

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