Appellate courts should defer to trial judges' findings on witness credibility and fact unless convinced the decision is wrong, especially when the trial judge has personally observed the witnesses' demeanour.

Lord Alness:-

In this case the respondent, who is a sales manager, sued the appellant, who is a doctor, for damages. The claim was based on negligence. The respondent was treated for malaria by the appellant, and the former affirms that, in giving him a quinine injection in the right buttock, the appellant travelled beyond the safe area for injection, and that the quinine injured the respondent's sciatic nerve, with the result that be if permanently lamed. The claim made by the respondent against the appellant was based upon two grounds: (1) that the appellant negligently inserted the needle of a hypodermic syringe into the sciatic nerve in the right buttock of the respondent, and/or negligently injected quinine into the said nerve, or, alternatively, injected quinine so near to the said nerve as to injure the same and destroy the tissue of a portion of the sciatic nerve; (2) that the appellant had not the skill and knowledge necessary for the administration of the said injection, or alternatively, in breach of his duty to the respondent, negligently omitted to exercise the necessary skill or knowledge when administering the said injection. The learned trial Judge in the Supreme Court of Trinidad and Tobago (Mr. Justice Manning) had no hesitation in holding that the appellant had the necessary skill and knowledge for administering intramuscular injections in the buttock with safety, and that he had considerable experience in such administration. Their Lordships are accordingly, absolved from considering that aspect of the case. But the question of the appellant's alleged negligence remains for consideration, and manifestly the result of that enquiry is of much importance to both parties to the suit. In its elucidation the Board received valuable assistance from the Bar.

The statement of claim by the respondent was dated 25th April 1932. The defence was filed on 31st May 1932. Evidence was led on 22nd October 1932, and for three weeks thereafter. The learned trial Judge delivered judgment in favour of the respondent on 7th October 1933. The Board cannot refrain from expressing their appreciation of the care and the fairness which characterise his judgment. Now, the first observation which falls to be made is that their Lordships are manifestly and indeed admittedly confronted with a pure question of fact for determination. There is no question of law at issue between the parties. Moreover it is agreed between them that the onus of proof is upon the respondent, and that, if he is to succeed, he must demonstrate, beyond reasonable doubt, that the appellant was negligent, and that his negligence caused the injury of which the respondent complains. Had the case been tried by a Judge and Jury, their Lordships are of opinion-and Mr. Pritt did not seriously contest the proposition -that an appeal against a verdict for the respondent would be well-nigh hopeless. There is ample evidence to support such a verdict, and it could not be seriously contended that a verdict for the respondent would on, the evidence led, have been unreasonable. The case, however, was not tried by a Judge and Jury, but by a Judge sitting as a Jury. The distinction is, of course, important. The appellant is exercising a right of appeal which is his by right, and their Lordships recognise that they cannot, merely because the question is one of fact, and because it has been decided in one way by the learned trial Judge, abdicate their duty to review his decision, and to reverse it, if they deem it to be wrong. Nonetheless, the functions of a Court of appeal, when dealing with a question of fact, and a question of fact moreover in which, as here, questions of credibility are involved, are limited in their character and scope. This is familiar law. It has received many illustrations-and, in particular, in the House of Lords- the most recent of these being the case of Powell and Wife v. Streatham Manor Nursing Home , (1935) AC 243=104 LJ KB 304=79 SJ 179=51 TLR 289. In