Herring. Criminal Law: Text, Cases, and Materials (8 edn, 2018). p. 728 last para.
By contrast with the House of Lords, the view taken here is that a conviction for a stigmatic offence is a sanction in its own right and that sanctions should be confined to the blameworthy. The non- conviction of the blameless should be a pervasive principle of substantive criminal law limited only by the need to theorize and practise criminal law as a system of rules and by the exigencies of forensic practicability. Those limitations entail that many ‘normal’ life narratives cannot afford grounds of excuse, however exculpatory the force of the narrative may be. But other accounts, not currently represented in standard defences, can be brought within the framework of substantive criminal law. If it can be done it should be done in order to diminish the incidence of unnecessary criminal convictions.
I can't even infer which of the two meanings of "forensic"!