Jesus's corpse would've been identifiable simply by its location1 (Note: They knew were Jesus's tomb was.) This is relevant because it renders corpse decomposition irrelevant.
The combination of these durably recognizable features were dead giveaways for identifying Jesus's corpse:
Fleshly lacerations/holes in his…
• …head (from thorn-crown),
• …back (from scourging),
• …side (from spear thrust),
• …and feet and wrists (nail holes),
And more generally…
• …Jesus's height and stature, hair, and teeth (a surprisingly recognizable feature to friends/family).
The corpse's environment was also very preservation-friendly:
• It was chilly/cool, likely well-below the º70 F proposed by Lüdemann.1
• It was arid.2 This is relevant because a corpse can avert decay for decades in a sufficiently arid environment.3
This holds all especially true in first few weeks following Jesus's death, when Christians were already upsetting the Jews and winning converts (e.g. see Acts 1-2).
Jn 18:15-18, 25 -- “[Just before Jesus' crucifixion, one disciple] entered with Jesus into the court of the high priest, but Peter was standing at the door outside [the disciple] spoke to the doorkeeper, and brought Peter in… Now the slaves and the officers were standing there, having made a charcoal fire, for it was cold and they were warming themselves; and Peter was also with them, standing and warming himself. …, Simon Peter was standing and warming himself.” (b) Contemporary investigations suggest that it would have been cold:
• Robert Gundry (NT scholar, professor at Westmont): “…the high elevation of Jerusalem can make it cold at Passovertide. …” [Mark: A Commentary on His Apology for the Cross (Eerdmans, 2000), 997.]
• Raymond Brown (NT professor at New York [d. 1998]): "Actually, it can be quite cool in mountainous Jerusalem in early spring;” [The Gospel according to John XII-XXI (Doubleday, 1970), 982.]
• William Lane Craig (NT scholar, specialist in the Jesus-resurrection debate: “Jerusalem, being 700 meters above sea level, can be quite cool in April.” [Assessing the New Testament Evidence for the Historicity of the Resurrection of Jesus (Edwin Mellen, 1989) 204.]