Recently two former popes have been canonized as saints by the Catholic church. According to the book Saints for Dummies these are the requirements a person must meet before before being considered a saint by the church.
To become canonized as a saint, a perfect track record isn’t required (or possible). Hence, being sinless isn’t on the list. So, what is required for sainthood?
Two verifiable postmortem miracles.
Evidence of having led an exemplary life of goodness and virtue worthy of imitation, having died a heroic death (martyrdom), or having undergone a major conversion of heart where a previous immoral life is abandoned and replaced by one of outstanding holiness.