It was reported that more than 500 people saw him alive after he was crucified, but the point is testimony is so important that our entire system of justice is based on it....and nothing else.
No, you do not have 500 eyewitnesses of Jesus' resurrection. What you have is a claim by one
person, Paul, that 500 other
people--who are not named, who produced no accounts, drawings, or records of their own that can be traced to them--saw Jesus. If I were to say, "5,000 people in Taos, New Mexico saw an alien spacecraft land in the Taos Plaza," would you nod and say, "Whelp, there's the testimony of 5,000 people proving that alien spacecraft visit Earth, so I'm a believer!" I sincerely doubt you would.
Furthermore, it is not clear in what sense these alleged people "saw" a resurrected Jesus. In the same passage, Paul lists his own experience of "seeing" Jesus, and he uses the same word for "see" as he does with the others he speaks of. Paul's experience was a mystical vision of light shining down from the sky. The vision-entity had to tell
Paul that it was Jesus. Paul did not recognize him as such on sight, and he certainly had no way to verify that what he was seeing was Jesus and not Satan leading him away from the truth of Judaism, or some 12-year-old space alien playing a prank, or a hallucination in his own head. We have no way to know if the alleged 500 others also "saw" Jesus in the same way, assuming they're real to begin with.
The extreme paucity of detail (no time(s) and place(s) where the encounter or encounters took place, no description of the event itself or any words Jesus spoke at the time, and not the slightest indication of "where are they now?") casts doubt on the validity of the claim. At the very least, these alleged 500 people would have claim to some sort of special status in the Christian community, relative to people who did not see Jesus. The fact that the Five Hundred are not mentioned in other Christian epistles and correspondence, nor does anyone make reference to any grand, timeless words Jesus uttered to them, provides a pretty good argument that this was a non-event.
In the hands of a believer, this claim also puts the lie to the notion that Jesus has to hide and be coy. If he can "appear" in some way to 500 people, what's to stop him from showing up at Billy Graham crusades to receive the altar call? Why can't he visit the churches who worship him in spirit and in truth? And not in some invisible, indistinguishable-from-his-not-being-there way, either. That would certainly solve the problem of "false" Christians or churches, which has been a huge
problem for Christianity throughout its history. If "free will" or some other excuse prevents him from being as detectable as any other real entity, why didn't that stop him from making this alleged appearance to the Five Hundred?