The mystery object that killed Rutger Hale while he was driving on State Highway 6 near Lake Hawea last year almost certainly came from an oncoming vehicle.
An inquest into the 22-year-old's death, held in Queenstown yesterday, also heard evidence of an unidentified vehicle stopping and returning to the scene of the fatality.
It has raised more questions around what Coroner Richard McElrea described as a "classic freak accident".
Mr Hale died after being struck in the head by an object which crashed through the windscreen of his Subaru station wagon and exited through the rear windscreen early on October 24, 2013.
The object has never been found or identified, despite an extensive search and scientific analysis of residual material in the vehicle.