The proviso may be applied even where there has been material procedural unfairness in the admission of expert evidence, provided the appellate court can assess the strength of the Crown case and is satisfied beyond reasonable doubt of guilt on the remaining evidence. Fresh evidence adduced on appeal that demonstrates errors in prosecution evidence may simultaneously strengthen the Crown case if it confirms the correctness of the most critical aspects of that evidence. Where an expert's evidence is shown to contain material errors, this does not necessarily render the entirety of the evidence inadmissible — it is a case of incorrect opinions requiring qualification, not inadmissible evidence.
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