1. The Respondent (Defendant below), a foreign national, was charged with one count of drug trafficking. The main issue at trial would have been one of the Defendant’s knowledge: did he know he was carrying dangerous drugs, or might he have believed he was not carrying drugs with him but confidential documents, as he claimed on his arrest? 2. Before the trial began, the parties proposed to adduce, by way of admitted facts, a series of WhatsApp messages extracted from the Defendant’s mobile phone as evidence (“WhatsApp evidence”). But the Judge, of her own motion, decided to examine the admissibility of the WhatsApp evidence, and ruled that it was inadmissible as the Defendant’s mobile phone was allegedly mishandled by the investigating officers (“voire dire ruling”). 3. Following the voire dire ruling, the Defendant contended that he could not receive a fair trial as he was unable to adduce the WhatsApp evidence, which would support his defence as to knowledge. On this basis, the Defendant applied for a permanent stay of proceedings. The Judge allowed the application (“stay decision”). 4. Subsequently, the Prosecution notified the Judge of its intention to appeal against the stay decision to the Court of Final Appeal. Despite this, the Judge granted the Defendant bail on terms permitting him to leave Hong Kong, which he duly did. 5. There were four issues arising on this appeal: (1) whether the Prosecution could challenge the voire dire ruling; (2) whether the voire dire ruling was flawed; (3) whether the stay decision was wrong; and (4) how the Judge should have approached the question of bail and whether she was wrong in her approach. Challenge to the voire dire ruling 6. A decision to grant a permanent stay of proceedings was a final decision appealable to the Court under section 31 of the Hong Kong Court of Final Appeal Ordinance (Cap.484). 7. Although the voire dire ruling was an interlocutory decision, it was the basis of the stay decision. Thus, the Court held that the Prosecution could challenge the correctness of the voire dire ruling as part of the appeal against the stay decision. Whether the voire dire ruling was flawed 8. The Court held that the Judge’s ruling against the admissibility of the WhatsApp evidence was wrong. 9. First, the Judge mistakenly proceeded on the assumption that the WhatsApp evidence was being tendered by the parties to prove the truth of the contents of the communications, which would have engaged the common law rule against hearsay. In fact, the WhatsApp evidence was relied on only to demonstrate that the messages had been received by the Defendant. Thus, the hearsay rule and the statutory exception to that rule provided by section 22A of the Evidence Ordinance (Cap.8), to which the Judge referred in the voire dire ruling, were both irrelevant. 10. Secondly, the Judge confused the issue of admissibility with the weight and reliability of the WhatsApp evidence. The WhatsApp evidence was relevant to the Defendant’s knowledge of whether he had been carrying drugs or confidential documents. On its face, the WhatsApp evidence was authentic and neither party had raised any issue as to its authenticity. The WhatsApp evidence was therefore admissible and the Judge had trespassed on the role of the jury in purporting to decide on its weight and reliability and in ruling it inadmissible. Whether the stay decision was wrong 11. The Court held that, as the stay decision was decided solely on the basis of her erroneous voire dire ruling, it followed that the Judge wrongly exercised her discretion in granting a permanent stay of proceedings because she took an erroneous, and therefore irrelevant, factor into consideration. Approach to bail pending appeal 12. The Court reviewed the statutory regime and held that the Judge erred in granting bail. The starting point was to ask whether the Defendant would be detained but for the stay decision. In the absence of any material change in circumstances, it would be inappropriate to release a defendant on bail conditions that might give rise to a substantial risk of his being absent, as the Defendant’s absence would then frustrate the Prosecution’s ability to proceed with the prosecution if the appeal were to succeed and, in practice, render the appeal ineffective. Disposition 13. Accordingly, the Court unanimously allowed the appeal. 14. It was ordered that the stay decision and the grant of bail be set aside, and the Prosecution be allowed to list the matter before another judge of the Court of First Instance to seek such orders for the prosecution to proceed, if possible.