Taub v The Queen

In the case of Taub v The Queen, the appellant was charged with manufacturing a large commercial quantity of a prohibited drug. The primary evidence against the appellant was the opinion of a police expert that the appellant had manufactured a large commercial quantity of the drug. The High Court of Australia was tasked with determining whether the appellant's conviction was unreasonable or unsupported by the evidence. The central legal issue was whether the assumptions underlying the expert's opinion must be proved for the opinion to be admissible.

The court examined the exceptions to the opinion rule, focusing on the basis rule and the proof of assumption rule. The basis rule permits an expert to give evidence of their opinion on an ultimate issue, provided that the basis of their opinion is proved. The proof of assumption rule requires that the assumptions underlying an expert's opinion must be proved for the opinion to be admissible. The court concluded that the proof of assumption rule did not apply in this case because the expert's opinion was not based on assumptions that were outside the common experience or knowledge of the jury. Instead, the court held that the basis rule applied, and since the basis of the expert's opinion was proved, the opinion was admissible.

The court further held that the appellant's conviction was not unreasonable or unsupported by the evidence. The expert's opinion, based on the quantity of the drug produced, was sufficient to support the verdict. The court found that the jury was entitled to accept the expert's opinion as reliable and that there was no error in the trial judge's direction to the jury regarding the weight to be given to the expert's opinion. The court dismissed the appeal and affirmed the appellant's conviction.