A trial judge may not, in response to a jury question, direct on extended common purpose (McAuliffe foresight) when the Crown case has been expressly confined to concert and aiding and abetting. Such a direction impermissibly expands the prosecution case and exposes the accused to criminal liability on a distinctly different basis. Extended common purpose requires proof of actual subjective foresight; an objective test ('ought to have known') is erroneous.
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