Inspired by How long was Jesus in the tomb?How long was Jesus in the tomb?, the question could be reasonably raised "if Jesus was only in the tomb for a day and a half, can we be sure that he really died, or were the witnesses mistaken?"
I'm looking not simply for biblical assertions by the biblical authors that Jesus died on the cross, but more objective facts about what happened. For example, if he got cold and blue, or if rigor mortis set in, or if the tomb began to smell, this type of data would be supporting evidence of his death.