The church has always been very cautious and careful about who could be accepted and honoured as saints. It doesn’t just rely on the devotion of the ordinary people. In the early church, the local bishop and neighbouring bishops were responsible for making a very thorough enquiry into the sanctity of the person’s life, and into the miracles attributed to the person’s intercession. In the case of martyrdom all the circumstances surrounding the person’s death had to be very carefully investigated. Only the Pope could declare a person to be a saint for the universal church. Eventually in order to avoid passable abuses, the Pope through the Congregation for the Causes of Saints in Rome, took over the responsibility of overseeing the whole process leading up to the official recognition of a person as a saint. But the ordinary faithful would still be involved.
Soon after their deaths the church authorities, seeing the faith and devotion of the faithful, initiated very thorough canonical or legal enquiries into how Mother Teresa and Pope John Paul II had lived their faith, and practiced the Christian virtues especially the virtues of faith, hope and love. After interviews with many witnesses who knew them very well, the enquiries concluded that both these candidates for sainthood had indeed lived their faith in a truly heroic manner. These canonical enquiries also found that both of them were powerful intercessors with God, on behalf of people who prayed to them for special favours.