What does John 19:34 mean?
Most crucifixion victims died within hours, or days, in unspeakable agony. This could come by infection, thirst, exposure, animals, blood loss, or shock. In most cases, Roman crucifixion ended in suffocation, as victims lost the strength to push against their impaled limbs to breathe. To speed this up, executioners might use a heavy rod to shatter the victim's shin bones. Jesus has been crucified alongside two men (John 19:18), who suffer this fate (John 19:31–32). Jesus had been savagely maimed before being crucified (John 19:1), however, so He has already died (John 19:30). This is obvious enough to the executioners that they don't even make the effort to break His legs (John 19:32).For whatever reason, one of the attending soldiers decides to be sure Jesus is really dead. A spear thrust is much quicker and easier than a messy blow to the legs, especially when one knows the target is already dead. The result of this attack is a gush of blood and water. John, who describes this scene, was very close to Jesus when it happened (John 19:25–27). The gory, graphic image of bodily fluids pouring out of Jesus' side left no doubt that He was dead. Were Jesus in perfect health prior to this moment, such an injury would have been fatal. In this situation, it's evidence that Jesus succumbed to blood loss and shock as fluid built up around His heart. There is no question, at all, that He's dead.
Among the sillier claims made about Jesus is that He survived the crucifixion. Some claim He then pretended to have been resurrected, or simply escaped. What Jesus experienced, however, was enough to kill Him several times over. Scourging victims often died from their injuries (John 19:1). Infection, shock, and blood loss from crucifixion were fatal (John 19:18). Having a spear impaled through the chest, resulting in a gush of fluid, is an immediately lethal wound. A person left locked in a tomb for three days would have succumbed to infection and dehydration (Matthew 28:1–10). There is no reasonable way to suggest that Jesus survived all these things, only to convince people later that He was a victorious, resurrected Messiah.
Having a first-hand look at this graphic scene, and knowing that Jesus is indisputably dead, leads John to emphasize His own account in the next few verses (John 19:35).
