Nienstedt wrote that the archdiocese's policies and procedures "may not have been uniformly followed and that is a serious issue we have been addressing."
The archbishop also defended the archdiocese's refusal to release the names of priests accused of sexual abuse.
"There are no offending priests in active ministry in our archdiocese," he wrote. "Anyone who is a known danger to a minor or vulnerable adult is immediately removed from ministry and investigated. There are, however, priests and other members of the clergy who have been falsely accused and exonerated. ... Clergy members should be given the same rights as other citizens."