Clearly, a 'circumstantial' ambit for duties of care in tort is more black/white: there can be no breach if there is no duty, and it thus equates to 'strict impunity' (as was formerly applicable, for example, to barristers in courts of law); which, it might be argued, is open to abuse and justifiable only by recourse to 'policy' considerations (viz. an overriding public interest; lesser of two evils, etc.). On the other hand, the imposition of 'standards' of care in breach allows for greater discretion on the part of the judiciary albeit potentially at the expense of 'policy', contingent on the relative dispositions of the judges trying a given case. Obviously, there can be no 'right' answer to such a question; but then, that's pretty much the crux of the entire exercise.