THE QUEEN v. WAN PUI HAY

IN THE COURT OF APPEAL

1986 No. 471
(Criminal)

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JUDGMENT

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Kempster, J.A.:

1. This is the judgment of the Court.

2. On 5th September last year in the High Court Wan Pui-hay was convicted on the verdict of a jury of possessing a dangerous drug for the purpose of unlawful trafficking and sentenced by Deputy Judge Gall to a term of imprisonment. Against that conviction he seeks leave to appeal on the ground that there was no evidence fit for the consideration of the jury to establish that the bag found in his possession in a car parked off Mody Road on 18th March 1986 contained tetrahydrocannabinol as alleged by the Crown. This is a ground which involves some consideration of the hearsay rule which, as was pointed out by Lore Reid in Myers v. DPP[1] - is absurdly technical. Technical or not the applicant is entitled to rely on the law as it stands though it cannot be ignored that

The data of every science are enormous in scope and variety. No one professional man can know from personal observation more than a minute fraction of data which he must every day treat as working truths.Wigmore on Lvidence 3rd vol. 2 para. 665(b).

3. There was placed before the jury a certificate in due form purporting to be signed by the Government Chemist to the effect that the substance found in the bag was tetrahydrocannabinol. Having regard to the term of s. 25(1)(b) of the Evidence Ordinance (Cap. 8) it constituted prima facie evidence of its contents. Mr. Sedgwick, on behalf of the applicant, submits to us, as he submitted to the Deputy Judge, that the oral evidence given by Dr. Chan, the signatory and an expert, demonstrated that the content of the certificate was of no evidential value whatsoever and that its prima facie value was displaced since he had been in no position to certify as he did from his own knowledge. It is common ground that the definitive tests upon which both his certificate and his oral testimony were based involved comparison with a standard substance provided by the United States Pharmacopoeia warranted to constitute tetrahydrocannabinol. In other words Dr. Chan implicitly relied on the assurance of a third party who was not called to give evidence which, in general, the law stigmatises as hearsay evidence and regards as inadmissible. No attempt was made to challenge the authority of the American Pharmacopoeia and Dr. Chan described the standard as authentic and recognised world-wide.

4. But the law recognises exceptions to the hearsay rule and one of those exceptions applies to expert witnesses who are entitled to express opinions based on information, published or unpublished and usually in written form, received from other experts. Medical text-books constitute a prime example. The relevant information must be of a type generally and reasonably relied upon and falling for evaluation within the relevant field of expertise. As was stated by Wells J. in very similar case to this

it is now well settled that an expert, within proper limits, must be permitted to treat as a working truth data which he learns about from other experts. Reid v Kerr[2]

In the British Columbia Court of Appeal Anderson JA said of the use of a standard published by the National Institute of Health in the United States,

The analyst as an expert, was entitled to use such scientific data as he deemed necessary. No evidence was adduced to indicate that United States graph was not a reliable source. He was not cross-examined on this point. R. v Jordan[3]

Similarly Kerr LJ in R v Abadom[4]

In the context of evidence given by experts it is no more than a statement of the obvious that, in reaching their conclusion, they must be entitled to draw upon material produced by others in the field in which their expertise lies. - It seems to us that the process of taking account of information stemming from the work of others in the same field is an essential ingredient of the nature of expert evidence.

The exception in question is well recognized within this jurisdiction. As was stated by the Full Court after careful argument. in R v Leung Chi Kin[5]

In chemical matters as in other scientific and technical matters those concerned must inevitably place some measure of reliance on the work of others. As Blair-Kerr, J. has pointed out in R v Ma Wai Fun[6] , a nurse taking a temperature relies on the efficacy of the thermoneter and is not normally required to prove its accuracy or the manner in which it works. A chemist using different substances to carry out his tests will normally rely on the labels attached to these substances in his laboratory and, unless there is some special reason for raising the issue, will not normally be required to establish that he had personally tested each of these substances beforehand in order to show that they were what he thought them to be. A chemist or doctor who says that he took, say chloroform, from a bottle so labelled is not normally required to prove that he had personally examined and tested the contents beforehand, any more than he would be asked to prove from his personal knowledge that a glass slide was in fact made of glass before being allowed to refer to it as such.

5. Within the parameters already explained we see no ground in law or logic for distinguishing between words caused to be published by an expert in a text-book and those which he writes or causes to be written on a label then affixed to a bottle or substance. The Deputy Judge was right in directing the jury that it was open for them to find that the certificate constituted prima facie evidence of the nature of the substance found in the possession of the applicant and to give to it such weight as they saw fit in the light of the evidence as a whole. Wilband v. R[7].

6. In the premises and while we think it appropriate to give leave to appeal and to treat the hearing of the application as the hearing of the appeal the appeal itself must be dismissed.