HKSAR v. LAI WUN YIN

CACC 18/2020

[2023] HKCA 203

IN THE HIGH COURT OF THE

HONG KONG SPECIAL ADMINISTRATIVE REGION

COURT OF APPEAL

CRIMINAL APPEAL NO 18 OF 2020

(ON APPEAL FROM HCCC NO 66 OF 2018)

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J U D G M E N T

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Hon Zervos JA (giving the Judgment of the Court):

Introduction

1.  The appellant and Choy Ling Ling (“Choy”) stood trial before Alex Lee J (“the judge”) and a jury on a joint count of conspiracy to defraud, contrary to common law and punishable under section 159C(6) of the Crimes Ordinance, Cap 200, to which they both pleaded not guilty.

2.  It was alleged that they conspired together and with the appellant’s husband, Chun Chi-wai (“Chun”), and others to defraud the Hong Kong Stock Exchange (“HKEx”) by dishonestly submitting false financial results and information of China Metal Recycling (Holdings) Limited (“CMR”), thereby inducing the HKEx to approve the listing application of CMR to the Stock Exchange Main Board. The scheme involved the use of false financial results and information which was achieved by circulating funds between CMR and some of its purported customers and suppliers (the circular funds flow) to overstate the profits of CMR.

3.  On 19 December 2019, following a trial lasting 65 days, the appellant was convicted by a majority verdict of the nine-member jury of 7 to 2, while Choy was convicted by a unanimous verdict. On 23 January 2020, the judge sentenced the appellant to 7 years’ imprisonment and disqualified her from being a director of a company for 10 years, and Choy to 8 years’ imprisonment.

4.  The appellant was granted leave to appeal against her conviction by a Single Judge[1] in respect of the prosecution’s challenge of the defence handwriting expert, Mr Leung Sze Chung (“Mr Leung”, who was DW2 at trial). The ground of appeal is whether the prosecution can challenge the opinion of the defence expert when the expert engaged by the prosecution had given a similar opinion but had not been called to give evidence. Whilst the defence did not seek to have the prosecution expert give evidence, it raised the question of whether the prosecution’s challenge of the defence expert’s opinion was fair and proper in the circumstances[2].

Background

5.  It was common ground that Chun was the mastermind of the fraudulent scheme, the subject of the alleged conspiracy. He absconded prior to trial, and an arrest warrant was issued against him. Despite his absence, the prosecution case proceeded against the appellant and Choy. It was alleged the appellant was a knowing party to the conspiracy to defraud the HKEx, primarily due to her involvement in the corporate structure of CMR and several fraudulent transactions.

6.  In the public records of the company, it was stated that Chun and the appellant co-founded a group of companies under the corporate structure of Asia Steel (Holdings) Limited (“Asia Steel Holdings”), which was wholly owned by Chun. Asia Steel Holdings, which had operations both in Hong Kong and mainland China, was engaged in trading scrap metal, and its trading arm, Central Steel (Macao Commercial Offshore) Limited (“CSM”), was situated in Macau.

7.  It was eventually decided that Asia Steel Holdings would apply to be publicly listed on the HKEx, and for that purpose, CMR was incorporated in the Cayman Islands on 18 July 2007. Chun beneficially owned all the shares of CMR through a company called Wellrun, and the appellant became one of its non-executive directors.

8.  On 2 June 2008, CMR submitted its first application for public listing on the basis of the profit test, which, among other things, required during the three-year track period that its profit attributable to shareholders, in respect of the most recent year, had to be not less than HK$20 million, and, in respect of the first two years, the profit had to be an aggregate of not less than HK$30 million. However, because of the 2008 financial crisis, CMR could not proceed with the listing and therefore let the application lapse.

9.  On 24 February 2009, CMR submitted its second application for public listing. It again made its submission on the basis of the profit test, but the track record period was for the years ending 31 December 2006, 2007 and 2008. A number of documents were submitted to the HKEx in support of the application, including a draft prospectus[3], a draft accounts report on the financial information of CMR and its subsidiaries for the three-year track record period[4], a list of major customers and suppliers[5], a memorandum on profit forecast[6], and a memorandum on cash flow forecast[7]. All the directors of CMR, including the appellant, had signed documents confirming the accuracy of the information submitted, which the HKEx relied on when considering CMR’s listing application.

10.  The Listing Committee of the HKEx approved the application on 10 June 2009, and CMR issued a prospectus[8], inviting applications from members of the public to subscribe for its shares. On 22 June 2009, the shares of CMR were listed on the mainboard of the HKEx, and a total of about HK$1 billion was yielded from the initial public offering.

11.  About four and a half years later, on 28 January 2013, the trading of CMR’s shares was suspended. Eventually, in March 2015, the company was wound up by a court order, and provisional liquidators were appointed.

12.  There was no dispute that CMR and CSM’s financial information and records were largely false and highly exaggerated. A number of false companies were set up to create fictitious trading transactions. A treasury accountant (PW17) examined the financial and trading records of CMR and related companies, and she found that they were extensively based on false records and accounting. She conducted a funds flow analysis of selected bank accounts of the companies and observed that there was a circular fund flow among these selective bank accounts in that CSM paid a total of US$538 million to suppliers that paid a total of US$547.1 million to customers that finally paid a total of US$834.1 million to CSM. She found that the supporting documents of the transactions were false.

The prosecution case

13.  The prosecution case was that CMR based its listing application on a significant amount of materially false financial results and information, and deceived officers of the HKEx in the execution of their public duty in approving the application to list CMR publicly.

14.  CMR was described as purchasing scrap metal from overseas, which would then be resold. At all material times, Chun was effectively the controlling shareholder of CMR and also chairman of the board. At the time of CMR’s listing on the stock exchange, the appellant was a non-executive director of CMR.

15.  A key subsidiary of CMR was CSM, a wholly-owned subsidiary Macau company that acted as its trading arm. The appellant was a director of CSM during the track record period[9] but had become its non-executive director by the time the CMR prospectus was issued[10].

16.  A significant part of the trial was spent in proving the falsity of the financial results and information contained in the listing application. A shipping expert testified that a substantial portion of the bills of lading, which purportedly reflected shipments of scrap metal handled by CMR or its subsidiaries, could not have been genuine[11]. A treasury accountant testified that there was a circular fund flow among the bank accounts of CSM, its suppliers and its customers[12]. A major source of the circular fund flow was traced back to Chun[13]. The funds transferred by CSM remittance instructions initiated by the appellant ended up in the circular funds flow. It constituted 10% of the funds from CSM to its suppliers, 9.9% from its suppliers to its customers, and 6.8% from its customers back to CSM[14]. The gross profits of CMR were overstated by at least 32.5%, or up to 59.9%, depending on the method of calculation[15].

17.  It was revealed from the prospectus and various witnesses that the top suppliers, one of which was Cheung Fat Metal Recycling Limited (“Cheung Fat”), and customers of CMR were vehicles set up by staff of CMR. This was disclosed by two clerks, who constituted nearly the entire complement of staff at CSM in Macau, despite it purportedly being involved in multi-million dollar transactions in the trading and shipping of scrap metal.

18.  It was the prosecution case that the appellant was significantly involved in CMR as evidenced by the following[16]:

(a)  The appellant held multiple directorships in the CMR group of companies throughout the years[17]. During the track record period, she had been a director of CSM since 17 July 2007, four subsidiaries[18] of Asia Steel Holdings and three other subsidiaries[19] of CMR. She was a director of the predecessor of CMR and a co-founder with Chun of CMR. At the time of CMR’s listing in June 2009, she had become a non-executive director of CMR and four of its subsidiaries, including CSM. She was among some other directors who had been granted share options in CMR.

(b)  The appellant was a businesswoman in her own right. She had a room in the office of CMR. She remained a non-executive director of CMR until it was wound up. She was the sole shareholder and director of Aprima Logistics Limited (“Aprima”) and Worldwide International Inspection Limited (“Worldwide”), two supposedly unrelated companies of CMR[20].

(c)  One of the bank remittances of Aprima, in the amount of US$5 million, was involved in the circular funds flow identified by the treasury accountant. The remittance application in which Aprima transferred the US$5 million to a customer of CMR was alleged to have been signed by the appellant (this was the subject of dispute at trial and will be referred to as the “Aprima remittance”).

(d)  A cheque from Worldwide in the amount of $7,900 signed by the appellant, was alleged to have been used to set up a supplier of CMR, namely Cheung Fat. There was no evidence as to how the appellant came to sign the cheque.

(e)  The appellant was one of the two authorised signatories for CSM’s bank accounts with DBS Bank (Hong Kong) Limited, Macau Branch (“CSM Accounts”). According to the bank records, she was made an authorised signatory on 3 August 2007[21], some 3 months before the first of the 22 CSM remittances were initiated by the appellant on 21 November 2007[22], which formed part of the circular funds flow. The appellant signed remittance applications of CSM, which amounted to 10 % of the total movement of funds from CSM to Cheung Fat and Lane Tone Hong Kong.

(f)  The appellant, in her capacity as a non-executive director of CMR, attended the “long board meeting” (customary in preparing the listing applications) at the solicitors’ firm on 22 May 2009 and signed various documents for the listing, including a letter of responsibility in which she confirmed, amongst other things, that the contents of the prospectus were accurate.

19.  For the purpose of the trial, experts were engaged to examine and give an opinion on the signature purportedly signed by the appellant on the Aprima remittance. Dr Hui Wing Sze, Janesse (“Dr Hui”), the Government Forensic Scientist, was engaged by the prosecution to examine the questioned signature. Her expert report dated 2 September 2019 formed part of the unused material, which had been disclosed to the defence as required. The report was not produced into evidence at trial, and she was not called as a witness by the prosecution. Nor was she requested by the defence to be tendered for cross-examination.

20.  It is noteworthy that the expert opinions of Mr Leung and Dr Hui in respect of the questioned signature were congruent except for some minor differences. So far as material, Mr Leung stated in his report:

“4.1.1 In this case, both the questioned signature and the known exemplars are copies. The examination was as a result hampered. Original documents are preferred so that the questioned signature in comparison with the specimen signatures can be scrutinized in detail with the aid of various instruments and methodology. The writing activity involves movements, not only on a 2-dimensional plane but also the application of pressure on the paper surface. Copying is a reproduction process transforming a somewhat 3-dimensional figure into a 2-dimensional image and is unavoidably subject to inherent limitations of the resolution achievable by the machine, as well as distortion and loss of detail during copying.

…

4.3.1 The questioned signature of Ms. Lai Wun Yin … was examined and compared with the corresponding known signatures … The questioned signature is pictorially similar to the control signatures. Being copies, examination for structural details, stroke connection, writing movements and typical features of forgery, such as delicate retouching and inconspicuous pen lifts etc. cannot be made. Despite these limitations, certain differences from the known signatures were found.

4.3.2 Although the questioned signature is a copy of rather poor quality, there is evidence indicating that it exhibits poor line quality. It is especially notable that the upper part of the oval appears to be somewhat angular in shape … On the contrary, the known signatures generally curve smoothly at the top of the oval …

…

4.4.1 Since the questioned signature and the known exemplars are copies, detailed examination of line quality, connection characteristics, writing movements as well as diagnostic features of forgery, such as delicate retouching and inconspicuous pen lifts etc. cannot be made. However, the pictorial appearance of the questioned signature does indicate that it probably exhibit poor line quality compared to those control signatures.

…

5.2 Whilst the questioned signature is a copy of rather poor quality, it nevertheless exhibits certain differences from the known exemplars with respect to morphology, alignment characteristics and relative position. Additionally, there are indications of the questioned signature displaying unnatural writing movements and poor line quality.

5.3 Considering the findings and the limitations, I am of opinion that the signature on the questioned fax copy of DBS Bank Application for Telegraphic Remittance … was probably not written by Ms. Lai Wun Yin, whose known signatures are present … The opinion is qualified on the assumption that the writing attributes depicted from the questioned signature and the known exemplars are present on the original documents.

5.4 The opinion expression adopted is based on a 9-point opinion scale of: (i) written by, (ii) highly probably written by, (iii) probably written by, (iv) may have been written by, (v) inconclusive, (vi) may not have been written by, (vii) probably not written by, (viii) highly probably not written by, (ix) not written by.” (Emphasis added)

21.  So far as material, Dr Hui stated in her report:

“3. A number of significant limiting factors was present in this examination:

(a) The questioned signature … and the control signatures … were all photocopies in which delicate writing attributes relating to pen pressure variations and subtle features could not be unequivocally deciphered as compared with the original documents. In addition, any evidence of tracing or retouching would not be readily identified on photocopies. The present examination would have helped with the availability of the original documents.

(b) The questioned signature was relatively simple in design and hence embodied very limited subtle writing characteristics useful for the identification of authorship and it was also susceptible to imitation, distortion or disguise.

(c) Within the control signatures, they displayed natural writing variations relating to the slant and length of the first upward writing strokes, shape and size of the oval shape loops, number, lengths and shape of turnings after the oval shape loop, and writing direction of the ending strokes. Changes in slant of the upward strokes and size of the oval shape loops of the control signatures were observed with time; from a more upright strokes and smaller oval shape loops in 2006 to the more forward slanting strokes and, wider and larger oval shape loops in 2007 onwards.

…

5. Nevertheless, comparison of the questioned signature … with the control signatures written by LAI Wun-yin … revealed differences in naturalness and rhythm of writing movements and the following characteristics writing features:

…

(a) In the questioned signature, a slightly upward bend was found at the beginning of the relatively short straight stroke, which started to curl up from midway of the slanting stroke and form the oval shape loop, in contrast to those displayed fluency and vigor, with relatively long straight strokes and started to turn at ends to form the oval shape loops, particular those control signatures written from 2007 onwards.

(b) An angular and awkward turning was found at the upper side of the oval shape loop in the questioned signature, in contrast to those smooth and round turnings observed in all of the control signatures.

(c) The arrangement of the zig-zag stroke in the questioned signature was regular with sharp angular turnings, blunt, uniform in shape, descending in lengths but similar lateral distance in between. On the contrary, those turnings in the control signatures displayed swinging and carefree motions, inconsistent in shapes and lengths, and varied distances in between.

(d) The imaginary baseline of the three bottoms of turnings were arranged regularly in an ascending manner in the questioned signature; while those were irregular and most of them were arranged in descending manner in the control signatures.

…

6. In view of the above findings, particularly the difference in rhythm of writing movements, while taking into consideration the absence of the original questioned signature and original contemporaneous control signatures submitted for examination, I am of the qualified opinion that the questioned signature … may not have been written by LAI Wun-yin who wrote the control signatures …” (Emphasis added)

22.  The prosecution cross-examined Mr Leung on the basis that: (i) he had only examined faxed copies of the signatures, which were of poor quality[23]; (ii) the same person could write signatures containing significant differences, to which Mr Leung agreed that there could be “natural variations” in signatures written by the same person but, depending on various factors, he disagreed that the same person could write signatures with differences[24]; and (iii) that a signature examination was less of a “scientific” and “quantified” discipline.

The defence case

23.  The appellant’s main defence was that she was not involved in the affairs of CMR and only held shares or directorships in CMR’s corporate structures because she was the wife of Chun. Evidence from the prosecution showed that the appellant seldom visited the offices of CMR, her office was mostly empty, and she had never visited the offices of CSM in Macau. The defence contended that the appellant was not involved in the operation of CMR and had no particular role in the company. Furthermore, the appellant had not exercised her share options and derived no benefit from the alleged conspiracy.

24.  The appellant did not give evidence at trial. She called Mr Leung to give expert evidence regarding the signature on the Aprima remittance application, which he said was “probably not written by” the appellant. In her qualified opinion, Dr Hui, who had been engaged by the prosecution, concluded that the questioned signature “may not have been written by” the appellant[25]. It was stated that she had taken into account the limitation raised by the prosecution, namely, that, despite the signatures she had examined being photocopies, she was still able to compare the rhythm of writing movements and writing features when arriving at her conclusion[26]. She also noted that the control signatures allegedly written by the appellant displayed “natural writing variations” but that she was able to identify a trend of the changes from the year 2006 to 2007[27].

The appellant’s submissions

25.  Mr Martin Hui, SC, with him Mr Dixon Tse and Ryan Chan, for the appellant, submits that the cross-examination of Mr Leung was not conducted on a “good faith basis” and was therefore unfair. He derives this principle from various common law cases. He points out that the wide discretion afforded to counsel in cross-examination was nonetheless constrained by counsel’s duty to carry out cross-examination responsibly and properly[28]. Mr Hui refers to the Canadian Supreme Court case of R v Lyttle[29] for the proposition that, although a question can be put to a witness in cross-examination regarding matters that need not be proved independently, counsel must have a “good faith basis” for putting the question[30]. Mr Hui suggests that the way the cross-examination was conducted put Mr Leung in a difficult position and may have created the impression that Mr Leung was not to be believed, despite the consistency of his evidence with the prosecution’s own expert.

26.  Mr Hui notes that the expert engaged by the prosecution, Dr Hui, had only considered “the lack of original copies” a limiting factor[31] and that it was not her opinion that this would render the assessment inconclusive. This was significant because the prosecution, however, challenged Mr Leung on the basis that faxed copies were of poor quality, and Mr Hui complains that this emphasis was done without a “good faith basis”. Mr Hui supplements that Dr Hui was still able to give an opinion, albeit a qualified one, based on the differences in naturalness and rhythm of the writing movements of the relevant signatures despite this “limiting factor”[32].

27.  Mr Hui further submits that Dr Hui considered the natural writing variations found in the control signatures a limiting factor, but that did not deter her from arriving at her conclusions. The prosecution however, relied on such factor to challenge Mr Leung’s methodology. When putting this into context, Mr Hui submits that the prosecution, by way of cross-examining on this aspect, was attempting to illustrate that the appellant could have potentially written very different signatures at different times or occasions[33].

28.  Mr Hui argues, since Dr Hui was not of the opinion that such a matter would affect the conclusion of the assessment of signatures, the prosecution should not have attempted in its cross-examination to inject bias into the application of Mr Leung’s expertise. Mr Hui submits that the challenge to Mr Leung to the effect that he had failed to factor in the possibility that a person could adopt different signatures or that the appellant may have changed her signature at different education levels was without a basis in good faith because there was simply no evidence to support such suggestions.

29.  Finally, Mr Hui submits that when the prosecution suggested that Mr Leung’s expertise in signature examination was less of a “scientific” and “quantified”[34] discipline, it did so without a good faith basis, especially when the prosecution had also sought an opinion from Dr Hui who was in the same discipline. The only purpose of this line of cross-examination was to undermine Mr Leung’s credibility.

30.  As an adjunct to the issue engaged in this appeal, Mr Hui criticises the prosecution’s invitation to the jury to compare signatures without calling its own handwriting expert. He submits that it was not proper for the prosecution to have asked Mr Leung, and in turn the jury, to compare certain signatures for the following reasons.

31.  First, the prosecution was effectively asking the jury to engage in the impermissible task of making their own comparison of the signatures so as to come to their conclusions when they did not have the relevant training or expertise. He suggests this was inconsistent with the judge’s direction to the jury that they should not do their own comparisons[35]. Such direction given to the jury could not have cured the improper and erroneous cross-examination and would have likely confused them.

32.  Secondly, it was wrong for the prosecution to have alleged that the questioned signature was written by the appellant when it was unable to produce a relevant expert opinion. He submits that what appears to have happened was that the prosecution “split” its case by attempting to adduce “expert evidence” through cross-examination of Mr Leung. This “splitting” of the case was unfair to the appellant as the appellant had conducted the trial on the basis that the prosecution would not adduce any expert evidence in relation to the signatures. He referred to Kissel v HKSAR[36], where counsel’s submission was recited by the Court, which said[37]:

“If evidence is relevant in any way to prove the case for the prosecution, it is the duty of prosecution to produce it as part of its case rather than to hold it back and introduce it by means of the cross-examination of the accused. To pursue the latter course is to engage in the error of splitting the prosecution case and to potentially deprive the accused of the opportunity of cross-examining the witnesses who might otherwise be called.”

33.  Mr Hui submits that the prosecution’s suggestions being made in cross-examination without a good faith basis presented a particular practical problem for the jury, as they would reasonably assume that a “responsible counsel would not make such suggestions unless there was some justification for them in his or her brief”[38]. The unfair challenges by the prosecution may have given the jury the impression that the prosecution at least had some expert advice contrary to Mr Leung’s opinion, which ultimately influenced their analysis of the case.

The respondent’s submissions

34.  The respondent is represented by Mr Newman Wong, who also represented the prosecution at trial.

35.  Mr Wong submits that all the questions asked of Mr Leung by the prosecution were within the permissible bounds of cross-examination of an expert witness as set out by Lamer J in R v Howard[39]. The prosecution was entitled to question Mr Leung to test and challenge his methodology and reasoning in order to enable the tribunal of fact to assess his opinion and what weight, if any, should be given to it.

36.  Mr Wong adds that if the present case concerned expertise based on “scientific evidence”, it could be argued that the prosecution cannot fairly challenge a defence expert who had reached similar results to the prosecution’s own expert because such challenge may necessitate a departure from the factual conclusions of the prosecution’s expert and therefore would not be made in “good faith”. He points out that the present case is distinguishable for the reason that the topic in question contains aspects of “judgment, assessment, and opinion”, and whilst there are objective and subjective elements in the expert evidence, the conclusion to be given involves a degree of interpretation and judgement. Accordingly, the prosecution was entitled to test the veracity of Mr Leung’s opinion based on his subjective interpretation.

37.  Mr Wong contends that if there is such a restriction on the prosecution as suggested by the appellant, the inevitable logical outcome would be that the prosecution was bound by the “qualified opinion” of Dr Hui, who was not a witness in the case and whose opinion also contained elements of subjective interpretation. He argues that there is no authority to support such a proposition. He also adds that had Dr Hui been requested to give evidence at trial, the prosecution would have been entitled to examine her conclusions by asking the same questions that were put to Mr Leung.

38.  In respect of the appellant’s complaint that the jury may have had the impression that they could compare signatures on their own, Mr Wong denies that the prosecution ever invited the jury to do so. More importantly, the judge gave clear directions to the jury, and there was no confusion on this aspect.

39.  Regarding the suggestion that the jury may have treated the prosecution’s suggestions put to Mr Leung as expert evidence, Mr Wong submits that there was no basis for such an assertion. He also rejects the contention that the prosecution’s cross-examination may have given the jury the impression that there was some expert advice contrary to Mr Leung’s opinion or that the cross-examination had improperly distorted Mr Leung’s real opinion or unduly undermined his credibility. He points out that the prosecution adduced other evidence to prove that the questioned signature belonged to the appellant. This was addressed by the judge in his summing-up to the jury when he reminded them of the following evidence[40]:

“… Also, as I have said, in order to determine whether the disputed signature was, in fact, made by D1, apart from DW2’s expert opinion, you are entitled to take into account all the relevant circumstances. You may think -- and it is a matter for you -- that the following may be relevant: (1) Lai was by Admitted Facts the only shareholder and director of Aprima; that is paragraph 14, the first set of Admitted Facts, P463. (2) according to the bank affirmation, P87, Lai was one of the two account signatory and the other one being her husband, Mr Chun, who you may think -- and it is a matter entirely for you -- would have little incentive to forge his wife’s signature anyway, he himself being a signatory himself. (3) if the disputed signature was not made by D1, then you may think -- and it is a matter entirely for you -- that the person who caused it would need to know that Aprima had a bank account with DBS -- and that is obvious -- and that D1 was a signatory of that bank account and how D1’s signature for that bank account was like. (4) you may think -- and it is a matter for you -- that the staff members of CSM or CMR would apparently have little incentive to forge D1’s signature on the remittance application, especially if you accept PW17’s finding, the treasury accountant’s finding, that the USD 5 million was used in money loop rather than have not been stolen or pocket by anyone.”

40.  Mr Wong finally submits that there was ample evidence of the appellant’s participation in the conspiracy in which the jury could return a guilty verdict, and therefore the conviction was neither unsafe nor unsatisfactory. He points out that the judge had properly directed the jury that they must not assume the appellant knew about or participated in the conspiracy by virtue of her spousal relationship with Chun[41], and that they could not find her guilty simply because they thought she was lazy or negligent in her duties as a director[42].

Discussion

41.  There are various classifications of evidence in our criminal justice system. One type of evidence is opinion evidence, which is different from the usual evidence presented in a criminal trial to prove or disprove facts in issue, although as noted in Phipson on Evidence, 20^th Edition[43], it may sometimes be difficult to identify the line that divides evidence of fact and evidence of opinion.

42.  Opinion evidence from an expert is permitted to provide the court with a basis for considering and understanding the evidence that might otherwise have little or no meaning. It is, therefore, not uncommon for experts to differ in their opinion on a particular topic or to qualify their opinion by various levels of certainty or uncertainty, as the case may be. Consequently, because of the unique character of this type of evidence, there is a body of requirements and restrictions regarding its relevance and admissibility, as well as the form it may take if allowed to be received into evidence.

43.  The English Court of Appeal in R v Luttrell[44] explained that for expert evidence to be admissible, two conditions must be satisfied: first, that study or experience will give a witness’s opinion an authority which the opinion of one not so qualified will lack: R v Bonython[45]; and secondly, the witness must be so qualified to express the opinion. If these two conditions are met the evidence of the witnesses is admissible, although the weight to be attached to his or her opinion must, of course, be assessed by the tribunal of fact: R v Robb[46]; R v Dallagher[47].

44.  The nature of expert evidence, particularly when it concerns handwriting analysis, is relevant to the approach taken by parties in addressing such evidence at trial. This was helpfully explained in Phipson on Evidence as follows[48]:

“Expert witnesses have the advantage of a particular skill or training. This not only enables them to form opinions and to draw inferences from observed facts, but also to identify facts which may be obscure or invisible to a lay witness. The latter might simply be described as ‘scientific evidence’, the former as ‘expert evidence of opinion’. A microbiologist who looks through a microscope and identifies a microbe is perceiving a fact no less than the bank-clerk who sees an armed robbery committed. The only difference is that the former can use a particular instrument and can ascribe objective significance to the data he perceives. The question of subjective assessment and interpretation which is the essence of opinion evidence hardly enters into the matter at all. An example of the dichotomy can be seen in the case of a conflict between experts on handwriting as to the authenticity of a document. By virtue of their training such experts would be able to distinguish parts of letters or techniques of word-formation which a layman would be unable to observe: this is the scientific part of their work. The question of which features are significant and the inferences to be drawn from them are questions of judgment, assessment, opinion. This distinction, which has now been accorded a measure of judicial recognition, is thought to be of some practical utility in considering the weight of evidence given by experts, both taken in isolation and when assessing the merits of two competing theories. …” (Citations omitted)

45.  As noted in this passage, expert evidence on handwriting involves an element of subjective assessment and interpretation, which may have a bearing on the weight to be placed on such evidence.

46.  In our view, it would be contrary to the fundamental principles of fairness for prosecuting counsel to contest a matter which he knows to be true or supported by substantive evidence. But at the same time, prosecuting counsel is entitled to challenge defence evidence to test its veracity and reliability. Cross-examination plays a crucial role in the adversarial process of a criminal trial to the benefit of both sides, and is of essential importance in determining whether a witness is credible or reliable. However, parties to criminal litigation should be able to conduct a full and proper cross-examination of a witness without significant and unwarranted constraints. The examination of a witness is subject to a body of principles so as to ensure that the proceedings are conducted fairly and properly focused on the issues at trial. The principle of a “good faith basis” as articulated in Lyttle highlights the important professional duties and ethical responsibilities of a trial counsel.

47.  In the present case, prosecuting counsel challenged the quality and reliability of Mr Leung’s opinion that the signature in question was “probably not written by” the appellant. Even though Dr Hui expressed a similar opinion, the significant feature, in this case, was that they both heavily qualified their opinions because of the material on which they were based. The issue, therefore, is not so much that the two experts came to a similar conclusion but rather the basis of their conclusion and the qualifications they made in arriving at their opinion.

48.  Mr Leung acknowledged that his examination had been hampered because the questioned signature and examples were copies and not originals. He made the observation that the copying of the document was subject to inherent limitations of the resolution achievable by the machine that made the copy, as well as “distortion or loss of detail” during the copying process. He added that he could not examine for structural details, stroke connection, writing movements and typical features of forgery, such as delicate retouching and inconspicuous pen lines, et cetera. Not surprisingly, Dr Hui made similar comments concerning the “number of significant limiting factors” that were present in her examination of the signatures.

49.  When Mr Leung was called to give evidence on behalf of the appellant, he was examined by defence counsel on his opinion that the questioned signature did not belong to the appellant. He acknowledged that there were “limitations” in the examination of the signatures because he had not been provided with the originals[49]. He also acknowledged that the questioned signature was of “very poor quality”[50] and went on to discuss the differences between the known signatures of the appellant and the questioned signature. He was examined about the difficulties in evaluating in respect of photocopies and the sorts of features or characteristics he would look for or identify in forming his opinion. He explained the issues that may arise when forming an opinion in relation to handwriting examinations compared with other areas of forensic science, and that because of the limitations the opinion given could not be absolutely certain[51]. In light of the matters raised in Mr Leung’s examination-in-chief, it was quite in order for prosecuting counsel to question him about these matters in cross-examination. He was asked questions about the number of samples involved in making a comparison with the questioned signature, the differences in the signatures, the issue of distortion of the signatures due to the quality of the photocopy or fax copy of the signature, his evaluation and analysis of the signatures, and the element of subjectivity in the examination[52].

50.  It was open to prosecuting counsel not to call Dr Hui to give expert evidence if he did not accept the correctness or reliability of her opinion because of the limitations and qualifications she identified in addressing this matter or other evidence that was contrary to her opinion. Mr Wong submits that an instance when this had happened was the case of HKSAR v Kissel[53], in which prosecuting counsel did not call a psychiatrist whom the prosecution had consulted because he did not accept the psychiatrist’s opinion, but he still challenged the defence expert on the issue of diminished responsibility. No issue was taken regarding the prosecution’s approach to this aspect of the evidence.

51.  In the circumstances of the present case, we do not consider it improper or inappropriate for prosecuting counsel to have cross-examined Mr Leung in the manner he did. He was examining matters that arose from examination-in-chief and was legitimately pursuing a line of enquiry on matters pertaining to Mr Leung’s opinion. Moreover, the expert evidence of Mr Leung was not the only evidence regarding the questioned signature. There was other prosecution evidence which went to establish that the questioned signature belonged to the appellant, and this also provided a basis on which to cross-examine Mr Leung, or Dr Hui for that matter, as to his opinion that the signature was “probably not written by” the appellant.

Conclusion

52.  For the above reasons, we find that the appeal must fail, and accordingly, it is dismissed.