The Apostle John is the most credible, unimpeachable witness to the life, death, and resurrection of Jesus Christ.  He was one of the first disciples to be called by Jesus.  He witnessed every major event and miracle in the ministry of Jesus, including the transfiguration and the resurrection, and he was the only disciple to witness the crucifixion.  It is clear John was the beloved disciple whom Jesus prepared for a much longer and a more important ministry than the other disciples, more important than even Peter.  The testimony of John is Exhibit One for the Good News of Jesus Christ.