I often hear talk on Catholic Answers Forums that even though a priest may be offering Mass unworthily (in a state of mortal sin) that you still receive the same graces you would as if you received the sacraments from a priest who is in a state of sanctifying grace. And the Council of Trent does indeed teach that the Holy Mass cannot be contaminated by the malice of priests. St Alphonsus de Liquori, Doctor of the Church says that when a priest offers Holy Mass in a state of mortal sin, he is striking Jesus with his own hands. And St Augustine says, "Those that unworthily offer Jesus Christ in heaven sin more grievously than the Jews who crucified Him when he was upon earth."
Isaias 1:15 And when you stretch forth your hands, I will turn away my eyes from you: and when you multiply prayer, I will not hear: for your hands are full of blood.
St Theresa of Avila, while approaching the Communion rail one day, once saw a devil on each side of a priest who celebrated Mass in the state of mortal sin. The devils trembled in the presence of the Holy Sacrament, manifesting the desire to flee. From the consecrated Host, Jesus said to St Theresa, "Behold the force of the words of consecration, and see, O Theresa, My goodness which makes me willing to place Myself in the hands of my enemy for your welfare, and for the welfare of every Christian."
Pray every day for the sanctity and holiness of our priests. Their responsibility before God is tremendous, and they need our prayers.