By David Shepardson WASHINGTON (Reuters) – U.S. auto safety regulators said on Thursday they found no evidence of defects in a Tesla Motors Inc car involved in the death of a man whose Model S collided with a truck while he was using its Autopilot system. The case has been closely watched as automakers race to automate more driving tasks without exposing themselves to increased liability risks. Tesla Chief Executive Elon Musk, on his Twitter account, praised the decision by the National Highway Traffic Safety Administration, which did not order a recall and put the responsibility for the accident primarily on the driver, former Navy SEAL Joshua Brown.