According To New York Times, Ukraine officials are convinced Iran would not have admitted to downing their plane had missile debris not been found at the crash site.
A warhead missile part was recovered on the crash site and Iran admitted they downed the plane in error after days of denying that they were behind the crash.
Iran first accused the cabin crew of the doomed aircraft to have made a sharp that brought them closer to their military intelligence base hence their decision to down it, before retracting the statement and saying they brought the aircraft down in error the cabin crew did nothing wrong.
More: New York Times