I know that saints are people who were especially holy and who devoted their lives to God, many of them also being martyrs; but when does a saint become a saint? For instance, if Pope John Paul II is eventually canonized as a saint, would he become a saint then or is he already a saint in Heaven right now?When the Church declares that someone is a saint, she is affirming something that is already true. All men receive their eternal reward immediately upon their death. If the reward is heaven, then that soul is a saint. All souls in heaven are saints. When the Church investigates the particular life of one of these souls and declares it to be a saint, she does not make it a saint when it was not one before. Instead, she is affirming for the faithful, "it is acceptible to believe that this soul is in heaven, and to pray to this soul with the veneration that is due the saints."
Note also that we have saints on earth as well as in heaven. Paul, in particular, calls anyone a saint who lives a life of grace in right relationship with the Lord.