Ping!
The first two, below, being Roman military ‘regulations’ are proof enough for anyone who knows anything about the Roman Army — Whoops, that is really a miniscule group of people. Ah, the ‘minutia’ that is common knowledge to those of us who are military historians.
(1) Jesus could not have survived crucifixion. Roman procedures were very careful to eliminate that possibility. Roman law even laid the death penalty on any soldier who let a capital prisoner escape in any way, including bungling a crucifixion. It was never done.
(2) The fact that the Roman soldier did not break Jesus’ legs, as he did to the other two crucified criminals (Jn 19:31-33), means that the soldier was sure Jesus was dead.