Barnett's death has come just a week after he gave a formal deposition in which he was questioned by Boeing's lawyers, before being cross-examined by his own counsel. He was to undergo further questioning on Saturday, for which he failed to appear. Later, his body was found in a parking lot.
The US authorities have been trying to bring Snowden back to the United States to face a criminal trial on espionage charges. If proven guilty in the US court, Snowden may face prison for up to 30 years.