Chief Justice Ma: A. INTRODUCTION 1. After hearing submissions, the appeal was allowed and it was ordered that the appellant be released from custody. These are the Reasons for allowing the appeal. 2. The issue before the Court was whether it was in the interests of justice to order a second retrial for the appellant in relation to a charge of trafficking in dangerous drugs.[1] In the present case, after allowing her appeal, the Court of Appeal had made an order for a second retrial.[2] 3. Unusually, the Appeal Committee of the Court of Final Appeal[3] granted leave to appeal on the substantial and grave injustice limb[4] to enable the appellant to argue against the order for a second retrial. I say “unusually” because the discretion whether or not to order a retrial after the allowing of an appeal in criminal proceedings is usually best left to the Court of Appeal to determine based on the interests of justice.[5] 4. Leave was granted on the basis that it was reasonably arguable the Court of Appeal had been wrong in the exercise of its discretion by not sufficiently taking into account “the undue hardship and unfairness allegedly occasioned to the [appellant] by the second retrial order, particularly given her psychiatric condition and the further deterioration of her condition said to have resulted from the order”.[6] In support of this ground, leave was given by the Appeal Committee to adduce a medical report of the appellant’s mental condition, as well as to prepare a joint expert report on the appellant’s current psychiatric condition and also on her fitness to stand trial for a third time. The appellant’s mental condition had been raised in the Court of Appeal and there was medical evidence placed before the court. Essentially, it was said that she was suffering from “adjustment disorder”. The appellant was diagnosed with Major Depressive Disorder (MDD) after the hearing before the Court of Appeal. I shall go more into this aspect later. A.1 Facts and procedural history 5. The facts pertaining to the trafficking charge are relatively simple. On 15 November 2012, the appellant arrived in Hong Kong from Kuala Lumpur. At Hong Kong International Airport, her suitcase was inspected. After unzipping the lining of the suitcase, a customs officer found 2 packets containing 1.79 kilogrammes of a mixture having 0.8 kilogrammes of heroin hydrochloride. The appellant was accordingly charged with the trafficking offence. 6. The appellant was first tried before a jury in February 2014. After a 6-day trial, she was convicted on a 5:2 majority verdict and sentenced to a term of 21 years’ imprisonment. In February 2015, her first appeal to the Court of Appeal was dismissed. However, she was given leave to appeal to the Court of Final Appeal in May 2016 and in February 2017,[7] her appeal was allowed on the basis that inadequate directions had been given to the jury by the trial judge in relation to an equivocal statement that had been made by the appellant at the airport, this statement being alleged by the prosecution to constitute an admission of guilt. Her conviction was accordingly quashed. A retrial was ordered. 7. The second trial took place in July 2017, this time lasting some 14 days. The appellant was again convicted by another majority verdict (6:1). In August 2017, she was sentenced to a term of 21 years’ imprisonment. In August 2018, she appealed to the Court of Appeal. In November 2018, the Court of Appeal allowed her appeal[8] and quashed the conviction on the basis of another misdirection by the trial judge to the jury, this time in relation to the giving of adequate warnings to the jury, in particular as to whether lies allegedly told by the appellant or acts of concealment on her part could be relevant to proving the trafficking offence. As stated earlier,[9] in December 2018 the Court of Appeal ordered a second retrial and in November 2019, the Appeal Committee granted leave to the appellant to appeal to this Court. 8. Throughout this time, since November 2012, the appellant had remained in custody. Up to the hearing of the present appeal, she had therefore been in custody for about 7½ years. B. RETRIALS – THE RELEVANT PRINCIPLES 9. Section 83E of the Criminal Procedure Ordinance[10] states that the Court of Appeal, if it decides to allow an appeal, may order a retrial if “the interests of justice” so require. The jurisdiction to order a retrial is thus put in the widest possible terms. In HKSAR v Tam Ho Nam (No. 2),[11] Fok PJ restated the relevant principles regarding retrials by reference to Au Pui Kuen v Attorney‑General of Hong Kong,[12] Ting James Henry v HKSAR[13] and Kissel v HKSAR.[14] The following principles, distilled from the above and other cases, are relevant in the present case:- (1) Whether or not a retrial should be ordered is a matter of discretion. This discretion is usually exercised, as it should be, by the Court of Appeal, relying on their “collective sense of justice and common sense.”[15] And, as was put by Lord Bingham of Cornhill, there must be “an informed and dispassionate assessment of how the interests of justice in the widest sense are best served”; it is important to maintain “confidence in the efficacy of the criminal justice system.”[16] (2) The discretion whether or not to order a retrial depends entirely on what justice requires (this being the “critical question”[17]). (3) The interests of justice of course include a consideration of an accused’s interests and circumstances. The criminal justice system is there to bring matters to a conclusion without undue delay and without oppression; these are “accepted norms”.[18] It should be acknowledged that any criminal trial is to some degree an ordeal for the accused.[19] The interests of justice also include the interest of the public in seeing those who are guilty of serious crimes brought to justice and not escape merely because of a technical error in the conduct of a trial or in the summing up to a jury.[20] In Au Pui Kuen,[21] Lord Diplock referred to the following passage from the judgment of Gould Ag CJ in Ng Yuk-kin v The Crown:[22] that there may be cases where it “is in the interest of the public, the complainant, and the appellant himself that the question of guilt or otherwise be determined finally by the verdict of a jury, and not left as something which must remain undecided by reason of a defect in legal machinery”. In assessing the public interest, a court must take into account the views of the prosecution which is best qualified (and I would add has the duty) to present the views of the public[23], although it must ultimately be for the court to determine what is in the public interest. The strength of the prosecution case is also a relevant consideration. (4) The interests of justice require all relevant factors, both for and against a retrial, to be taken into account. Such factors will not only vary from case to case, but their relative importance and weight will also be different in any given case.[24] (5) The above said, one factor that must be given significant weight is the fact that the accused has already undergone a trial, in particular where the trial is long and complex.[25] This is all the more so when there is involved a second retrial, which means of course the possibility of a third trial for the same offence. In Mok Kin Kau,[26] the ordering of a second retrial after 2 concluded trials and appeals, and the serving of the whole sentence, was said to be an “unusual course” and in such a situation, in the absence of a special or compelling reason, this was a “departure from accepted norms” sufficient to constitute a substantial and grave injustice. Although it is not unprecedented for a second retrial to be ordered, the cases accept that this is an “unusual” course to take,[27] even where the accused has not served the whole of his or her sentence as was the case in Mok Kin Kau. Given that the ordering of a second retrial is an unusual course, a court would have to be persuaded by cogent and compelling reasons to make such an order. This is consistent with the interests of justice, but of course all relevant factors must be carefully weighed in this exercise of discretion. (6) Another factor that should also be taken into account is the time that an accused has spent in custody and in relation to this facet, the time that an accused has been in custody will have to be seen against the likely sentence that he or she might receive on a retrial.[28] 10. In common with the review of discretion in other areas, this Court will not disturb the exercise of discretion by the Court of Appeal in the determination whether or not to order a retrial unless there has been a serious error of law or principle or approach, such as where the court below has failed to take into account a relevant consideration or has taken into account an irrelevant one. Only in such a situation would the Court of Final Appeal be justified in exercising the discretion afresh. Furthermore, it is also important to emphasise that the relative weight which the Court of Appeal “ascribes to each relevant factor” is a matter within its discretion and it is not open to the Court of Final Appeal to seek to ascribe a different weight.[29] 11. I now deal with the application of these principles in the present case. C. APPLICATION OF PRINCIPLES 12. As mentioned earlier, the appellant’s mental condition was raised in the Court of Appeal. A Psychiatric Report from Dr Dorothy Tang[30] diagnosed the appellant to be suffering from adjustment reaction and situation reaction, although at the time of observation her mental condition was stable. However, as part of the psychiatric history, it was noted that her condition worsened when she had setbacks in legal proceedings. It was also noted that she harboured “fleeting suicidal ideation but she denied any concrete plan”. Reference was made to an occasion in December 2015 when she drank 2-3 mouthfuls of shampoo. An Incident Report Form detailed the incident. A letter dated 26 November 2018 from the Correctional Services Department to the appellant’s solicitors was also placed before the Court. The letter provided details of another incident (on 1 November 2018) when the appellant wounded herself with a comb. When seen by a clinical psychologist, she “admitted active self‑harm thought and counselling was provided to her”. 13. In ordering a retrial, the Court of Appeal made no reference at all to the evidence relating to her mental condition, merely stating: “The fact that the applicant has to face a third trial and that she has been remanded in custody for over 6 years, all of which might be causing her frustration but is insufficient to persuade this Court not to order the case for retrial.”[31] This was, with respect, at best a non‑appreciation and understatement of the appellant’s mental condition, particularly in the context of the lengthy time she had already been in custody and the fact she was facing a third trial. It was for this reason that leave to appeal was given that it was reasonably arguable a substantial and grave injustice had been done in making the order for a second retrial without adequate consideration of the hardship factor.[32] 14. In my view, the Court of Appeal was in serious error in its treatment (or non‑treatment) of the relevance of the appellant’s mental condition. It was a factor that had to be taken into account, particularly in the context of the time she had been in custody. If it had been properly taken into account, the Appeal Committee would not have been minded to grant leave to appeal. As it was not, this Court was accordingly free to consider afresh the exercise of the discretion whether or not to order a retrial. 15. The starting point in the present case was, since the prosecution was seeking a second retrial, that cogent and compelling reasons had to be advanced by it to justify this order. Furthermore, as stated earlier, up to the time her appeal was heard by this Court, the appellant had been in custody for 7½ years. It was not suggested that any part of this period was attributable to any fault on the part of the appellant. Even taking as optimistic a view as possible of the date for a retrial if one had been ordered (taking further into consideration the fact that a retrial may last 14 days[33]), it was likely that before the second retrial took place, the appellant would have been in custody for approximately 8 years without her guilt having been established. After both her previous trials, the appellant was sentenced to 21 years’ imprisonment. On the assumption that if she were convicted again and sentenced to the same term, after taking into account the allowance for good behaviour, the appellant would already have been in custody 8 years out of 14. This is over half of a long sentence, served even before she has been convicted and before the ordeal of yet another trial. This is the relevant context in which to evaluate the other relevant factors in the exercise of discretion in the present case. 16. Ms Maggie Yang for the respondent[34] did not dispute the relevant principles regarding retrials but emphasised two points in support of the order for a second retrial. First, she submitted it was in the public interest for the appellant to have to face trial for a serious offence. This is right: trafficking in dangerous drugs is without doubt a serious offence. The Court of Appeal said that the charge was “extremely serious”.[35] Secondly, Ms Yang also contended that the evidence against the appellant was strong. The Court of Appeal said that “the prosecution evidence supporting the charge is strong and compelling”.[36] This was correct inasmuch as the facts relied on by the prosecution are concerned: there was little dispute as to what occurred at the airport when the appellant was found in possession of a suitcase containing dangerous drugs. However, Ms Yang went further to enumerate a number of points to demonstrate that the appellant’s version of events – essentially to show that she had no knowledge of the fact that she was in possession of dangerous drugs – was incredible.[37] While I accept there is some force in these points, they cannot be taken too far. In relation to most, if not all, of these points, the Court of Appeal was of the view that they were open to question. It is also to be observed that the verdicts in the previous two trials were majority ones.[38] 17. I now turn to the medical evidence regarding the appellant’s mental condition. In granting leave to appeal, the Appeal Committee had given leave to adduce a medical report of Dr Tsang Fan Kwong as well as directed that a joint expert report be prepared on the appellant’s psychiatric condition to be considered in the present appeal. A Joint Psychiatric Report dated 7 January 2020 was prepared by Dr Tsang (the appellant’s expert) and Dr Tang (the respondent’s expert) and this was before us. As we shall see, the relevance of this evidence lay in putting into perspective the lengthy period the appellant had already been in custody. 18. There is a considerable amount of material before us including the said report of Dr Tsang and the Joint Psychiatric Report of Dr Tsang and Dr Tang. It is not necessary to deal with this material in detail but I would highlight the following:- (1) Although Dr Tsang and Dr Tang differed in their opinions on a number of matters, they were to varying degrees agreed that the appellant suffered from “[MDD], single episode, moderate to severe with psychotic‑symptoms”. This diagnosis followed the criteria laid down by the Diagnostic and Statistical Manual of Mental Disorder (5th edition) published by the American Psychiatric Association.[39] It is right to point out that Dr Tang was of the view that the appellant’s depression may not have been as severe as Dr Tsang diagnosed, that she may be in “partial remission” and that she appeared to be responding to medication she had not received prior to seeing the two doctors, but Dr Tang did agree with the diagnosis of MDD, albeit perhaps on a moderate scale. Dr Tang also said this: “[the appellant] is impressed to have inadequate stress coping skill, as evidenced [by] the discrepancy between her stable mental condition during the day in [Siu Lam Psychiatric Centre], and anxious‑look with slow response when she thought about the appeal and court hearing in clinical interviews”. (2) Notwithstanding the above diagnosis of MDD, both doctors were of the view that the appellant was mentally fit to stand trial. As was said in the Joint Psychiatric Report, Dr Tsang stated that “She understands the nature of the alleged offence. She is able to instruct a lawyer. She is able to follow court proceedings. She knows the difference between pleading guilty or not.” (3) That said, it is nevertheless clear from the Joint Report that the appellant was significantly stressed when reminded of the ongoing court proceedings. Dr Tsang was of the view that due to her depression, “her energy, confidence, attention, concentration and memory capacity were substantially impaired” and that it would “be a very difficult task for her to defend herself in a third trial”. Dr Tang was less pessimistic about the appellant’s ability to defend herself in a trial, but was nevertheless of the view: “Court hearing is an undoubtedly stressful experience, thus stress coping strategies and relaxation exercise would be continuously discussed with [the appellant].” See also her view as quoted in sub‑paragraph (1) above. 19. In view of the lack of agreement between the doctors as to whether or not the appellant would actually be disadvantaged in defending herself in another trial, Ms Yang submitted that this issue should not be determined by this Court and should instead be left to be decided by the Court of First Instance in an application for a stay of proceedings (a retrial being ordered in the meantime). Mr Khattak on the other hand argued that the issue should be determined by this Court. 20. I agree that the issue of whether the appellant would be unable properly to defend herself in another trial cannot be determined by this Court without hearing evidence from the doctors. However, the relevance of the medical evidence lay not so much in the resolution of this issue; rather, the relevance of the appellant’s medical condition lay instead in putting into proper perspective and context the lengthy period that the appellant had already been in custody in the present cases. 21. Taking all the above considerations into account, I am of the view that it was clearly in the interests of justice not to order a second retrial for the appellant. Perhaps individually, each factor may not necessarily be sufficient but cumulatively it was compelling to call a halt to the proceedings in the present case. Insufficiently cogent or compelling reasons existed to justify an order for a second retrial. D. CONCLUSION 22. For the above reasons, the appeal was allowed and the order for a retrial quashed, with the consequence that it was ordered the appellant should be released. Mr Justice Ribeiro PJ: 23. I agree with the judgment of Chief Justice Ma. Mr Justice Fok PJ: 24. I agree with the judgment of Chief Justice Ma. Mr Justice Cheung PJ: 25. I agree with the judgment of Chief Justice Ma. Mr Justice Stock NPJ: 26. I agree with the judgment of Chief Justice Ma. Mr Shahmim K Khattak, Mr Anthony Lai and Ms Holly Cheng, instructed by Annie Leung & Co., assigned by the Director of Legal Aid, for the Appellant Ms Maggie Yang, DDPP and Mr Franco Kuan, SPP, of the Department of Justice, for the Respondent [1] Contrary to sections 4(1)(a) and (3) of the Dangerous Drugs Ordinance Cap 134. [2] Yeung Ag CJHC, Poon and Pang JJA in a Determination dated 21 December 2018 [2018] HKCA 957 (the CA Determination). [3] Cheung Ag CJ, Ribeiro PJ and Fok PJ in a Determination dated 14 November 2019 [2019] HKCFA 41 (the AC Determination). [4] Section 32(2) of the Hong Kong Court of Final Appeal Ordinance Cap 484. [5] Section 83E of the Criminal Procedure Ordinance Cap 221 provides:- “83E. Power to order retrial (1) Where the Court of Appeal allows an appeal against conviction and it appears to the Court of Appeal that the interests of justice so require, it may order the appellant to be retried.” [6] AC Determination para 4. [7] (2017) 20 HKCFAR 71. [8] Yeung Ag CJHC, Poon and Pang JJA in a judgment dated 15 November 2018 [2018] HKCA 592. [9] See paras 2 and 3 above. [10] Set out in para 3 fn 5 above. [11] (2017) 20 HKCFAR 414. [12] [1980] AC 351. [13] (2007) 10 HKCFAR 632. [14] (2010) 13 HKCFAR 27. [15] Au Pui Kuen at 357D-E. [16] Forrester Bowe (Junior) v The Queen [2001] UKPC 19, at para 39. [17] Tam Ho Nam (No. 2) at para 21. [18] Mok Kin Kau v HKSAR (2008) 11 HKCFAR 1, at para 10. [19] Au Pui Kuen at 356H. [20] Au Pui Kuen at 357C-D. [21] At 359D-E. See also Dennis Reid v The Queen [1980] AC 343, at 350G-H. [22] [1955] 39 HKLR 49, at 60. [23] Ting James Henry at para 51. [24] Au Pui Kuen at 357D-E. [25] Ting James Henry at para 50. [26] At paras 12 and 14. [27] See Tam Ho Nam (No. 2) at para 24 referring to R v Chau Mei Ling [1981] HKC 542, at 545B-C; Mok Kin Kau at para 7; HKSAR v Li Yanhong (No. 2) [2016] 1 HKLRD 946, at para 14. [28] See, for example, Ting James Henry at para 52. [29] See, in the context of sentencing, Secretary for Justice v Wong Chi Fung (2018) 21 HKCFAR 35, at para 62. [30] A Visiting Psychiatrist at Siu Lam Psychiatric Centre. [31] CA Determination para 11. [32] AC Determination para 5. [33] Like the first retrial: see para 7 above. [34] With her, Mr Franco Kuan. Mr Shahmim Khattak, Mr Anthony Lai and Ms Holly Cheng appeared for the appellant. [35] CA Determination para 10. [36] CA Determination para 10. [37] These points are set out in para 38 of the respondent’s written Case. They largely consist of an assertion that the appellant was lying and attempting to cover up the truth. [38] See paras 6 and 7 above. [39] According to the criteria for a diagnosis of depression, in summary an individual must experience five or more of the following symptoms: 1. Depressed mood; 2. Diminished interest or loss of pleasure in almost all activities (anhedonia); 3. Significant weight change or appetite disturbance; 4. Sleep disturbance (insomnia or hypersomnia); 5. Psychomotor agitation or retardation; 6. Fatigue or loss of energy; 7. Feelings of worthlessness; 8. Diminished ability to think or concentrate; indecisiveness; 9. Recurrent thoughts of death, recurrent suicidal ideation without a specific plan, or a suicide attempt or specific plan for committing suicide. The appellant was found to have all 9 symptoms.