The involvement of Saul in the stoning of Stephen is generally seen as an established historical event - AD 34-35 - basically within a couple of years of Christ's bodily resurrection.
Many others were killed during the reign of the Roman Emperor Nero (54–68 AD), well within the lifetime of the 500+ eyewitnesses of Christ being around for 40 days after his crucifixion. They could have recanted if they knew it was false, but they knew it was true.
Many others were killed during the reign of the Roman Emperor Nero (54–68 AD), well within the lifetime of the 500+ eyewitnesses of Christ being around for 40 days after his crucifixion. They could have recanted if they knew it was false, but they knew it was true.