At the time of the Chinook accident, an 'Error of Judgement' was defined as 'an honest mistake, accompanied by no lack of zeal', if memory serves. Only rarely applied in HF accidents where the crew survived, perhaps because of the special care required in aircraft operations. Incidentally, you could not be found merely negligent; the board were required to assess the degree (minor/major/gross). The next level of blameworthiness I think was 'reckless'.