A jury of peers allows professional themselves to draw the line.
An effective way of organising the interpretation of the (intent of) human behaviour could be to create a “Just Culture Committee (or any other suitable name), with an as much as possible independent chair, with peers particiating in it. The peers must reasonably expect to see their own experience and professional judgement reflected in the end conclusion of the committee. This is essential for the justness of the conclusion. Make use of the navigator to assist in the interpretation of behaviour if necessary. Present the outcome of the committee to the manager of the person(s) involved for formal follow-up. Record the decisions.