On 14 October, Hamas handed over four bodies to Israel as part of the US-brokered Gaza ceasefire. Israeli forensic experts confirmed the identities of three of the bodies, but said that one did not belong to them. Hamas insistedthe fourth man was an Israeli soldier. The body, however, was that of Khalil Dawas, a Palestinian from Jericho suspected of working with Israeli forces. The Guardian’s Lorenzo Tondo explains what we know about his story – which is a tangle of contradictions, grey zones, secrecy and betrayal