United States | News & Politics

At the time of his death, Mr Barnett had been in Charleston for legal interviews linked to that case.

Last week, he gave a formal deposition in which he was questioned by Boeing's lawyers, before being cross-examined by his own counsel.

He had been due to undergo further questioning on Saturday. When he did not appear, enquiries were made at his hotel.

He was subsequently found dead in his truck in the hotel car park.