HKSAR v. Cheung Man Kong

CACC 29/2024

[2025] HKCA 1018

IN THE HIGH COURT OF THE

HONG KONG SPECIAL ADMINISTRATIVE REGION

COURT OF APPEAL

CRIMINAL APPEAL NO 29 OF 2024

(ON APPEAL FROM HCCC NO 221 OF 2021)

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J U D G M E N T

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1.On 23 January 2024, the applicant was unanimously convicted before Johnny Chan J (“the judge”) and a jury of one count of murder, contrary to common law and punishable under section 2 of the Offences against the Person Ordinance, Cap 212 (Count 1); and another count of assault occasioning actual bodily harm, contrary to common law and punishable under section 39 of the same Ordinance. He was sentenced to concurrent terms of life imprisonment and 6 months’ imprisonment on the two counts respectively. He has applied for leave to appeal in respect of his conviction for murder only on a single ground, which has been characterised by his counsel as a “question of law”. Of course, no leave would be required if the appeal is on a question of law alone: see section 82(2) Criminal Procedure Ordinance, Cap 221.

2.The question raised, as framed in the Perfected Grounds of Appeal against Conviction, is:

“whether it is permissible in law to admit the evidence of an expert witness, to draw adverse conclusions against a defendant based on general factual matters which the jury did not require the assistance of, and/or the receipt of such assistance/opinions/ evidence from an expert”.

The complaint concerns, in particular, the admissibility of the opinion of the defence expert witness, Dr Dorothy Tang (“DW2”), having viewed CCTV footage of the killing during her evidence, to the effect that the applicant had not lost his self-control.

The prosecution case

3.The offence took place during the afternoon of 1 September 2020, when the applicant, armed with a knife, which he had bought two days earlier, went to various MTR stations in Hong Kong looking for his former colleague, Mr Lee Wing-ho (“the deceased”). When the applicant eventually located him at Tseung Kwan O station, he attacked the deceased with the knife; and further assaulted Mr Lau Po-wing (“PW1”), another former colleague, who intervened to try and prevent the attack. The deceased died from his injuries suffered in the onslaught. The actual killing of the deceased by the applicant, which had been captured by CCTV at the scene and was witnessed by PW1, was not in issue.

4.According to PW1, the applicant took out a knife, rushed towards the deceased and stabbed at his head. PW1 tried to stop the applicant by pulling him from behind but the applicant continued to attack the deceased with the knife. The witness did not agree with the suggestion put to him by defence counsel at trial that the applicant was acting in a frenzy at the time[1].

5.The deceased suffered multiple wounds, and it became an admitted fact that he died of a “stab wound to chest with injuries to aorta and left lung”[2].

The defence case

6.The defences run at trial were threefold: (1) provocation; (2) diminished responsibility; and (3) lack of murderous intent. The applicant himself testified in his defence and called two defence expert witnesses, DW2 and Dr Choi Wing-kit (“DW3”), to establish that he was suffering from an abnormality of mind at the time of the incident.

7.The defence case was that, given how the applicant had been earlier treated, and in view of an event which took place on 30 August 2020 (see infra at [9]), the applicant was provoked to kill the deceased on 1 September 2020, when he lost control. The applicant was said to be undergoing a “delusional catathymic process” since he was suffering from borderline personality disorder and major depressive disorder, which led him to lose self-control and the ability to think rationally; further, his ability to exercise proper and reasonable control of his aggressive impulses was significantly impaired by his abnormality of mind.

The applicant’s testimony

8.The applicant had been receiving psychiatric treatment since 2002. He had been employed by Guardforce Limited (“Guardforce”) from November 2016 to June 2018 and had thereby become acquainted with the deceased. He described how his relationship with the deceased had deteriorated during his employment; as a result of which his mood worsened and he began entertaining thoughts of suicide, which required psychiatric treatment. In May 2018, he claimed that he had been “badmouthed” by the deceased, which had pushed him to his limit; thereafter, he began to have auditory verbal hallucinations, and subsequently resigned from his job.

9.On 30 August 2020, the deceased was on board a Guardforce vehicle with a colleague (PW7) when they both saw the applicant on the pavement staring and shouting at the deceased. The applicant later claimed that it was the unfriendly gaze of the deceased that had provoked him. Accordingly, he went to buy a knife that evening in order to protect himself out of fear that the deceased might hurt him. The applicant admitted that since 2018 he had had the idea of killing the deceased and of then committing suicide. That same evening, he went to Guardforce and followed the deceased but later lost sight of him.

10.On 1 September 2020, whilst working, the applicant had hallucinations in relation to the deceased. His mind became blank after returning home. He changed his clothes, put on a cap, picked up the knife and went to various MTR stations to look for the deceased in order to “teach him a lesson”. He eventually found the deceased at an ATM centre in Tseung Kwan O MTR station working with other colleagues (including PW1). The applicant hid behind a pillar and waited until it was less crowded. He then approached the deceased, took out the knife from his backpack and brandished it two to three times in front of the deceased. The deceased was injured by the knife twice and fell to the ground, after which the applicant kicked him in the head. The applicant fled but was eventually subdued by some passers-by.

Psychiatric evidence

11.DW2 and DW3 testified that the applicant had been suffering from borderline personality disorder since he was 13 years of age. However, their testimonies differed as to the applicant’s mental responsibility. DW3 considered that the applicant’s mental responsibility for his actions had been substantially impaired by major depressive disorder; while DW2 thought that the disorder was not operative at the time of the killing, since the applicant had not complained of pervasive or persistent low mood on a daily basis for at least two weeks[3].

12.In DW2’s opinion, the applicant could nevertheless be more easily provoked by the actions of others; the disorder constituted an abnormality of mind, but it may not substantially impair the rational judgment and self-control of the subject concerned.

13.During evidence-in-chief, DW2 was invited by the applicant’s counsel to watch the CCTV footage of the killing, in order to establish that the applicant had lost his self-control when he struck the deceased multiple times in a frenzied attack. However, having watched the CCTV footage, DW2 did not consider that the applicant had lost his self-control at the time of the killing, since (a) the attack was planned; (b) the attack was determined, he being undeterred by others who struggled with him to prevent the attack; and (c) after the attack, he returned to kick the deceased[4].

14.It was DW2’s opinion that, the applicant had the ability to exercise rational judgment over a period of time, which did not sit well with the notion of losing his self-control on the spur of the moment[5].

15.DW3, by contrast, was of the view that the unexpected encounter with the deceased on 30 August 2020 had pushed the applicant’s sense of hopelessness to an extreme; and in the following two days, under the influence of paranoid delusion, his emotions overwhelmed him, making him unable to think rationally, culminating in the idea that dying together with the deceased was the only solution to bring an end to his suffering. These disorders led the applicant to undergo a delusional catathymic process, which significantly impaired his ability to think rationally and to exercise proper control of his aggressive impulses.

Grounds of appeal

16.Mr Boyton, on behalf of the applicant, complains that the judge erred in allowing DW2’s opinion that the applicant had not lost his self-control during the killing to be elicited before the jury, following her viewing of the CCTV footage in open court. It was submitted that DW2 usurped the fact-finding prerogative of the jury on the questions of:

(i)  whether the applicant had as a matter of fact lost his self-control, in relation to the partial defence of provocation; and

(ii)  whether his mental capacity had as a matter of fact been substantially impaired for the purpose of the partial defence of diminished responsibility.

17.Mr Boyton contended that the opinion evidence of DW2 was inadmissible and had unfairly impacted on the ultimate issue before the jury.

Respondent’s submissions

18.Mr Cheng, with him Mr Chu, submitted that, although the evidence concerned did touch on the issue of whether the applicant had lost his self-control as a matter of fact, it was given at the behest of the applicant’s counsel, and it was related to the expert medical evidence.

19.In respect of the issue of provocation, Mr Cheng cited Attorney General v Holley[6], among other authorities, and submitted that evidence of mental illness, which made it more or less likely that a defendant had lost his self-control, was admissible in deciding the first subjective and factual ingredient, and also the first element of the second objective or evaluative ingredient concerning the gravity of the provocation for an accused.

20.He further pointed out that considerable latitude had been given to medical experts in testifying as to the ultimate issue: see R v Brennan[7], as accepted in HKSAR v Cheung Kie Chung[8].

21.Concerning DW2’s evidence and her comments upon viewing the CCTV footage, Mr Cheng submitted that, even though it was not made clear whether her comments related to the defence of provocation or diminished responsibility, the loss of self-control as a matter of fact was crucial to both defences. Since the applicant was relying on his mental illness to establish the two defences, medical evidence had always been admissible to prove loss of self-control. Indeed, both DW2 and DW3 had accepted that viewing the CCTV footage could shed light on these issues.

22.Mr Cheng further pointed out that the judge had made clear to the jury that they were not bound by DW2’s (or DW3’s) opinions, and the questions concerning the defence of provocation and diminished responsibility were for them to decide as the sole judges of the facts[9].

Consideration

23.Although the applicant has characterised the ground of appeal as ‘a point of law’, for which, if it were indeed a point of law alone, no leave would be required, the reality is that the point very much takes its context and substance from the facts of the case, the evidence from which DW2 derived her opinion and the way in which the evidence came about at trial. If one is examining the intrinsic admissibility of the evidence in question, then it needs to be remembered that it was the defence who sought to elicit the evidence from their own defence witness. Evidently, defence counsel did not get the answer he wanted. Encouraged by how the matter had developed with DW2, prosecuting counsel then sought to show the CCTV footage to, and ask the same question of, DW3, but it seems she did not get the answer she wanted either. Thus the two defence witnesses gave different responses to the question of whether the applicant had exhibited a lack of self-control and it was a matter for the jury, in conformity with the directions they received from the judge, to evaluate the expert evidence.

24.Those directions were as follows[10]:

“Unlike other witnesses, an expert witness is entitled to express an opinion on matters within his or her particular area of expertise. Other witnesses may speak only as to facts, that is, what they saw or heard, and are not permitted to express their opinion. Having said that, you should bear in mind that if, having given the evidence careful consideration, you do not accept the evidence of an expert witness, you do not have to act upon it. That is particularly so when the facts on which the opinion is based do not accord with the facts as you find them to be.

In the present case there is a conflict between the expert evidence of DW2, Dr Tang, and DW3, Dr Choi. And that conflict goes to: (1) the effect of borderline personality disorder. Both DW2 and DW3 diagnosed that it is likely that the defendant was suffering from borderline personality disorder at the material time of the offence. But their opinions differ as to the effect of this psychiatric illness had on the defendant; (2) whether the defendant was suffering from major depressive disorder at the material time of the offence. DW3 opines that it is likely that the defendant was, that he was suffering from major depressive disorder at the material time of the offence. DW2 disagrees with DW3’s diagnosis; (3) whether the defendant had lost his self-control when he attacked the deceased at the ATM centre.”

25.Shortly thereafter, the judge addressed the differences in the evidence of DW2 and DW3[11]:

“In considering the conflicting evidence of DW2 and DW3 in this case, you should consider factors such as their qualifications, how they expressed their opinions to you, how they responded to cross-examination, whether they appeared objective or, on the other hand, whether they appeared to be biased and overstated their evidence. You may wish to consider whether an expert witness has assumed the role of an advocate, whether he has stepped outside his area of expertise and whether his specialist experience is up to date and equal to that of those whose opinions he seeks to contradict. You should examine the quality of the reasons offered for an opinion and the facts which support it.

What the defendant told DW2 and DW3 and the past medical records of the defendant available to the experts played an important role in DW2 and DW3’s diagnosis of the defendant, that is, borderline personality disorder by DW2, borderline personality disorder and major depressive disorder by DW3. You should analyse the evidence of DW2 and DW3 and determine the extent to which the respective expert witness’ opinion depends on the facts or assumptions being correct. If the opinions based on facts which you are satisfied have been proved or assumptions that you are satisfied are valid, then it is a matter for you to consider whether the opinion that is based on those facts or assumptions is correct. On the other hand, if you decide that the facts have not been proved or the assumptions are not valid, then any opinion based on them is of no assistance because it has no foundation. If that is the case, the opinion should be disregarded.”

26.I would make the observation in passing that a frenzied attack does not necessarily equate with a loss of self-control (see HKSAR v Lo Chun Siu at [128]). In any event, by the above directions, the judge was making clear to the jury that the underlying facts were for them and them alone to decide. Furthermore, when addressing the law in relation to provocation, the judge directed that the question of the loss of self-control was ultimately one for the jury[12], but that in determining whether the applicant was caused suddenly and temporarily to lose his self-control,

“…you should have regard to the psychiatric illness or illnesses of the (applicant) at the time of the incident and the effect of the psychiatric illness or illnesses on the question whether he did lose his self-control”[13].

Thus, the issue of the applicant’s mental illness was relevant to the loss of self-control and, on that basis alone, it is difficult to see why the expert psychiatrists could not be asked the questions they were asked.

27.As to the more general question of whether an expert witness may be asked a question as to his or her interpretation of the facts, which goes to an important, or indeed ultimate, issue in the trial, the answer must be that it depends on the nature of the issues before the jury and the relevance of the expertise to those issues. Provided the judge makes clear in his directions, as he plainly did in this case, that the jury are free to take a different view of the facts on which the expert opinion is based, I see no harm or unfairness. And clearly, defence counsel had no qualms about asking the allegedly impermissible questions of DW2; nor did he object when prosecuting counsel traversed the same ground with DW3. Moreover, the fact that the two expert witnesses disagreed in their answers suggests that the matter was not clear cut, nor was it something on which they could not have had a valid difference of expert opinion. Whether the jury accepted either or neither of the opinions of the experts was a matter for them, as the judge made clear.

28.In the result, I do not regard the ground of appeal put forward as a question of law alone: rather, it is a question of law which takes its context and substance from the facts and evidence elicited in the course of the trial. It is, therefore, a question of mixed law and fact, for which leave is required.

29.I do not consider for the above reasons that the point is reasonably arguable on appeal and leave must accordingly be refused. I should remind the applicant that he has the right to renew his application for leave to appeal to the Court of Appeal, but he should also be informed that the Court has the power to order the loss of any time which the applicant has spent in custody pending his appeal, if it were to conclude that there was no justification for the renewal of the application.

Mr Raymond Cheng SADPP and Mr Jonathan Chu PP, of the Department of Justice, for the Respondent

Mr David Boyton, instructed by K B Chau & Co, assigned by the Director of Legal Aid, for the Applicant