The Church established the Inquisition to ensure that people who were not heretical were not convicted.

Confession is a requirement of Catholicism.

I quote:
"Jesus said to them again, "Peace be with you. As the Father has sent me, even so I send you." And when he had said this, he breathed on them, and said to them, "Receive the Holy Spirit. If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained"
--John 20:21-23

So, the Spanish Inquisition was nothing more than a confessional.

If the Church in 1492 AD deemed the converted Jews and Muslims who stood accused of falsifying their conversion to Catholicism to have no true intention of changing their ways, of lying to God himself about their true faith, the Church could withhold forgiveness, they would retain forgiveness, and hand them back to the King, for whatever punishment the King deemed appropriate.

But if the Church gave forgiveness, then the man walked free, the King had no authority any longer.

Everything done by the BOOK.