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Expert Evidence in Patent Cases


The scope of the article

This article deals with expert evidence in cases where the specification of a patent falls to be interpreted, and it aims to discuss the role played by an expert witness and the aspects that may be addressed by the expert witness. It does not purport to discuss the requirements for the validity of a patent, such as inventiveness and novelty. See s 25 of the Patents Act 57 of 1978 and Burrell South African Patent and Design Law 3rd ed (1999) at 31 et seq. A patent may, in general, be granted for any new invention which involves an inventive step and which is capable of being used or applied in trade or industry or agriculture.


The relevance of relevance

Relevance is the basic criterion for the admissibility of evidence. See Zeffertt, Paizes & Skeen The South African Law of Evidence (formerly Hoffmann & Zeffertt)  (2003) at 21. See also s 210 of the Criminal Procedure Act 51 of 1977, and s 2 of the Civil Proceedings Evidence Act 25 of 1965. The opinion held by a witness and the inferences made by him from the facts are usually irrelevant. In addition to the opinion of an expert, dealt with in this article, opinions are often received in evidence in circumstances under which it would be difficult to present the evidence without resorting to opinion: See Schmidt Bewysreg 4th ed (2000) at 457.

The court must evaluate the evidence and come to a decision. This function must not be abdicated to a witness.Schmidt points out [at 457] that this principle can be equated with the administrative law principle that a person to whom a function has been entrusted, must take a decision and may not abdicate that responsibility.

Evidence is relevant, and therefore admissible, if it can assist the court to make a finding. Schreiner JA once said that relevance is ‘based upon a blend of logic and experience lying outside the law’. [See R v Matthews 1960 (1) SA 752 (A) at 758B.]Relevant evidence has a ‘tendency in reason’ to prove material facts. [See rule 1(12) of the American Law Institute’s Model Code of Evidence.]In R v Mpanza 1915 AD 348 at 352, the Appellate Division stated that facts are ‘relevant if from their existence inferences may properly be drawn as to the existence of the fact in issue’. Relevance is ‘a matter of reason and commonsense’. [See Zeffertt, Paizes & Skeen at 219.]

In Ruto Flower Mills Ltd v Adelson 1958 (4) SA 235 (T) at 236-7, Boshoff J said that, generally speaking, relevant evidence is admissible and irrelevant evidence inadmissible. When the evidence of a witness cannot assist the court, his evidence is superfluous.For this reason also the opinion of an expert [For a discussion of the meaning of this term, see Menday v Protea Assurance Co Ltd 1976 (1) SA 565 (EC) ] is received when his skill in a particular discipline or field is greater than that of the court. [Joubert (founding ed) The Law of South Africa vol 9 sv ‘Evidence’ (by Schmidt & Zeffertt) 1st reissue (by Van der Merwe) (1996) par 506 at 340.] The expert witness is then permitted to state inferences only in so far as he has some special skill that enables him to interpret, or draw inferences from, the available data.[See Taylor & Pitt-Lewis A Treatise on the Law of Evidence 9 ed (1895) pars 1417–1425 at 931–938.]

Boshoff J referred to Taylor v Munro 43 Connecticut 44 where Loomis J stated the following:

‘The true test of the admissibility of such testimony is not whether the subject matter is common or uncommon, or whether many persons or few have some knowledge of the matter, but it is whether the witnesses offered as experts have any peculiar knowledge or experience, not common to the world, which renders their opinions founded on such knowledge or experience any aid to the Court or jury in determining the question at issue.’


In Cooper (SA) (Pty) Ltd v Deutsche Gesellschaft Für Schädlingsbekämpfung Mbh 1976 (3) SA 352 (A) at 370, Wessels JA pointed out that the opinion of experts is admissible when they are better qualified than the judicial officer to draw inferences by reason of their special knowledge and skill. Two situations must be distinguished: in the first, a court would be quite incapable of forming an opinion without the assistance of expert evidence, whereas in the second, the assistance of an expert would be useful.

The evidence of the expert may be opinion or fact, and the facts are often of such a nature that a trained eye is required to perceive it. [See Howard (general ed) Phipson on Evidence 15th ed (2000) par 37-1 at 917.]

Saying that the evidence of an expert is admissible when the expert is in a position to assist the court through his special knowledge and skill is just another way of saying that the evidence of the expert is admissible when it is relevant, and as a necessary consequence, inadmissible when it is irrelevant. This approach to the admissibility of expert evidence reflects the views of Wigmore Evidence in Trials at Common Law 4th ed (1961-8) vol VII par 1918, and is based on sound principle. It is to be preferred to the so-called traditional formulation in terms of which opinion evidence is generally inadmissible subject to a list of exceptions.

The Wigmore approach as well as the traditional formulation can be found in South African case law.[Zeffertt, Paizes & Skeen at 289.]

It is often said that a witness cannot state his opinion on ultimate issues - on the very question that the court has to decide. [See R v Van Tonder 1929 TPD 365; R v Louw 1930 CPD 368; R v Theunissen 1948 (4) SA 43 (C).] It is this facet of the traditional formulation of the rule relating to opinion evidence that is reflected in the statement that an expert is not entitled to tell the court what a patent specification means, or whether a step or alteration is obvious, since these are questions for the court to decide.

There are, however, many cases in which opinion evidence on ultimate issues is received by the court. [Joubert par 505 at 339. See also Rule 32 (2) of the Uniform Rules of Court.] Zeffertt, Paizes and Skeen argue, however, that a distinction between ultimate issues and other facts is not without merit.[Zeffertt, Paizes & Skeen at 294.]

When the court is not in a position to act on its own opinion because of a lack of special training or expert knowledge, the court must decide whether or not to accept the expert opinion. The court must be convinced that the expert is accurate. [See Ruto Flour Mills v Adelson at 237. See also R v Morela 1947 (3) SA 147 (A) at 151–153; R v Smit 1952 (3) SA 447 (A) at 451; Menday v Protea Assurance Co Ltd; Mahomed v Shaik 1978 (4) SA 523 (N); Joubert par 507 at 340.] It is also the function of the court to decide whether the expert is sufficiently well qualified to assist. A ‘bald statement of his opinion is not of any real assistance,’ rather, his opinion must be supported by evidence of the facts on which the opinion is based. [See Cooper (SA) (Pty) Ltd v Deutsche Gesellschaft Für Schädlingsbekämpfung Mbh at 371.]

The expert is simply in a better position than the court to form an express opinion on specialized subjects requiring special skill, experience, training, or exposure. As Gregorowski J once put it:

‘The judges cannot lay claim to the same experience and study, and if the experts had a fixed standard and could give their evidence with certainty, it would be folly for the Judges to differ from the opinions of the experts.’[Marais v Smuts (1896) 3 OR 158.]

The court is, of course, free to accept or to reject the evidence of any witness - that is the function of the court. [See Cooper (SA) (Pty) Ltd v Deutsche Gesellschaft Für Schädlingsbekämpfung Mbh at 370. See also Phipson Manual of the Law of Evidence for the Use of Students (1921) at 117.] It remains the duty of the court not merely to accept the opinion of an expert without satisfying itself that the expert is correct. [R v Baker 1932 EDL 228. See also National Bolts Ltd v Burg Products (Pty) Ltd 1988 BP 194 (CP) at 199.]

The expert witness may also have a conscious or unconscious bias in favour of one side or the other, because of preconceived notions and theories, and very often they are unlikely to deviate from an opinion once it had been formed. [See May South African Cases and Statutes on Evidence 4th  ed (1962) at 238.]



The general principles

The principles applicable to the interpretation of a patent specification, as they appear in Gentiruco AG v Firestone SA (Pty) Ltd 1972 (1) SA 589 (A) at 614–616,were restated in Monsanto Co v MDB Animal Health (Pty) Ltd (formerly MD Biologies CC) 2001 (2) SA 887 (SCA) at 891 par 8. Harms JA summarized the case law as follows:

‘(a)            a specification should be construed like any other document, subject to the interpreter being mindful of the objects of a specification and its several parts;

(b)            the rule of interpretation is to ascertain, not what the inventor or patentee may have had in mind, but what the language used in the specification means, i.e. what the intention was as conveyed by the specification, properly construed;

(c)            to ascertain that meaning the words used must be read grammatically and in their ordinary sense;

(d)            technical words of the art or science involved in the invention must also be given their ordinary meaning, i.e. as they are ordinarily understood in the particular art or science;

(e)            if it appears that a word or expression is used, not in its ordinary sense, but with some special connotation, it must be given that meaning since the specification may occasionally define a particular word or expression with the intention that it should bear that meaning in its body or claims, thereby providing its own dictionary for its interpretation;

(f)            if a word or expression is susceptible of some flexibility in its ordinary connotation, it should be interpreted so as to conform with and not to be inconsistent with or repugnant to the rest of the specification; and

(g)            if it appears from reading the specification as a whole that certain words or expressions in the claims are affected or defined by what is said in the body of the specification, the language of the claims must then be construed accordingly.’ [See also Bateman Equipment Ltd v Wren Group (Pty) Ltd 2000 (1) SA 649 (SCA) at 657 par 15.]


The role of the expert

When is the evidence of an expert admissible in interpreting a patent specification, and to what extent might the court rely on the evidence of an expert to assist it in the interpretation of such a specification?

Phipsonstated at 119 that while experts may state their opinions as to the meaning of technical terms contained in a specification, the state of scientific knowledge, the nature, working, characteristic features and probable mechanical results of the invention, what is old and what is new and what scientific advance has been made, and the similarities or differences between rival inventions, the expert may not state his opinion as to the construction of the specification, the question whether there is novelty, or the question whether the invention of one party infringes the patent held by another. [See also Howard pars 37-64 at 979]

In AECI Explosives Ltd v Ensign‑Bickford (South Africa) 1994 BP 42 (CP) at 46–47, MacArthur J said that the expert is not entitled to construe the specification or the claims. He can testify as to the state of the art but he is not entitled to say what the specification means. The expert may express an opinion on a given hypothesis as to whether the specification is capable of being carried into effect by a skilled worker. Guidance is the main function of an expert in a patent action. The special knowledge of the expert makes it possible for the Court to understand and construe the specification.

In SAPPI Fine Papers (Pty) Ltd v ICI Canada Inc (formerly CIL Inc) 1992 BP 165 (A) at 183–184, Corbett CJ said that the court must be instructed by expert evidence as to the state of the art as at the relevant date so as to enable the court to construe the patent specification. [See also McCauley Corporation Ltd v Brickor Precast (Pty) Ltd 1989 BP 314 (CP) at 317–318.]

The scope of the expert’s evidence

In Gentiruco AG v Firestone SA (Pty) Ltd 1972 (1) SA 589 (A) at 617-618 Trollip JA referred with approval to the decision in British Celanese Ltd v Courtaulds Ltd [1935] 52 RPC 171. This decision represented the law in force in the Supreme Court of Judicature in England as at 30 May 1961, which applies in South Africa as at that date in terms of s 42 of the Civil Proceedings Evidence Act 25 of 1965. [See also Van der Linde v Calitz 1967 (2) SA 239 (A) at 246–247.]

In the British Celanese case, Lord Tomlin expressed himself as follows on the role of expert witnesses:

‘The area of the territory in which in cases of this kind an expert witness may legitimately move is not doubtful. He is entitled to give evidence as to the state of the art at any given time. He is entitled to explain the meaning of any technical terms used in the art. He is entitled to say whether in his opinion that which is described in the specification on a given hypothesis as to its meaning is capable of being carried into effect by a skilled worker. He is entitled to say what at a given time to him as skilled in the art a given piece of apparatus or a given sentence on any given hypothesis as to its meaning would have taught or suggested to him. He is entitled to say whether in his opinion a particular operation in connection with the art could be carried out and generally to give any explanation required as to facts of a scientific kind.

He is not entitled to say nor is Counsel entitled to ask him what the specification means, nor does the question become any more admissible if it takes the form of asking him what it means to him as an engineer or a chemist. Nor is he entitled to say whether any given step or alteration is obvious, that being a question for the Court.’ [British Celanese Ltd v Courtaulds Ltd at 195.]

Lord Tomlin said that the disadvantages of permitting such inadmissible evidence to be presented the court, are that ‘time is wasted and money spent on what is not legitimate’, and ‘there accumulates a mass of material which so far from assisting the judge renders his task the more difficult, because he has to sift the grain from an unnecessary amount of chuff.’ [British Celanese Ltd v Courtaulds Ltd at 198.]

It is for the court to interpret a patent specification. [See Howard par 1-31 at 21.] Normally, the opinion of experts on what the specification means would be irrelevant, because the court could form its own view as to the meaning of the specification without opinion evidence by experts on that issue, but assisted by expert evidence on the meaning of technical terms and the way in which products or processes work. The opinion of the expert on what the specification means is then irrelevant and inadmissible for that reason, despite (it is respectfully submitted) the doubt expressed by Trollip JA in the Gentiruco case and which is referred to below.

<![if !supportLists]>2.4        <![endif]>The evidence of the expert must be relevant

It is submitted that in the final analysis the judgement in the British Celanese case is based on relevance. Compare, for example, the words of Lindley LJ in an earlier British case - Eddison and Swan Electric Lighting Company v Woodhouse and Rawson [1887] 4 RPC 99 at 108:

‘If the language is clear enough to guide competent workmen to enable them to obtain the desired result, we cannot see how a Court can hold the language insufficient in point of law. No doubt it is for the Court, and not for a workman, to construe the specification, but if a workman says it is a sufficient guide to him, and the Court believes him, the Court must hold that as regards clearness of description, the specification is, in point of law, sufficient.’

It is submitted that there can be no basis in principle for holding that an expert should not be allowed to say what a specification means to him, but that he should be allowed to say that the words of the specification is a sufficient guide to him, other than the basis of relevance.

Similarly, in Van der Lely NV v Bamfords Ltd [1963] RPC 61 (HL) at 71, Lord Reid rejected the argument that the interpretation of a photograph, like the interpretation of any document, is a question for the court, assisted where necessary by evidence regarding the meaning of technical language. His Lordship said:

‘Lawyers are expected to be experts in the use of the English language, but we are not experts in the reading or interpretation of photographs. The question is what the eye of the man with appropriate engineering skill and experience would see in the photograph, and that appears to me to be a matter for evidence. Where the evidence is contradictory, the Judge must decide. But the Judge ought not, in my opinion, to attempt to read or construe the photograph himself; he looks at the photograph in determining which of the explanations given by the witnesses appear to be most worthy of acceptance.’


This approach to the admissibility of expert evidence in a 1963 British case can once again only be reconciled with the principles underlying the British Celanese case on the basis of relevance. Normally, a court can determine the meaning of a document such as a patent specification on its own but the court may derive some assistance in interpreting a photograph, and for that reason the expert evidence on the interpretation of the photograph is admissible because it is relevant. It is relevant because the court can derive assistance from the opinion of the expert.

In the Gentiruco judgment, Trollip JA dealt with the question of usurpation by a witness of the functions of the court. [Gentiruco AG v Firestone SA (Pty) Ltd at 616–617.] The judge referred with approval to the Wigmore approach. He then stated that the opinions of experts on a highly complex subject of a scientific nature might have been of appreciable help, but concluded that the admission of opinion evidence on the meaning of the specification was precluded by the precedent of the British Celanese case.

It is not the function of expert witnesses to inform the court of the meaning of plain non‑ technical language in the claims of a patent. A matter involving such non-technical language has to be decided on the wording of the patent specification without the help of expert evidence. In such a case the court is as good a position as the expert to interpret the patent specification. In Multiknit 2000 (Pty) Ltd v Industrial Netting and Mining Products (Pty) Ltd 1997 BIP 97 (CP) at 100, Van Dijkhorst J said the following with reference to the parties:

‘Each was supported by an expert in the field of mining support structures. Without being disrespectful I must state that it is not their function to inform me of the meaning of plain non‑technical language in the claims of a patent. I accept their evidence on the state of the art prior to this invention but that does not take the matter much further than the recital of the prior art in the specification. This application has to be decided on the wording of the patent without the help of expert evidence.’


In Gentiruco at 618, Trollip JA thought it doubtful that the true reason for excluding the inadmissible opinion evidence is relevancy. He did however point out that irrelevant evidence is rendered inadmissible by s 2 of the Civil Proceedings Evidence Act.


A change in the law? The Ensign-Bickford decision

The approach in the British Celanese case to the admissibility of expert evidence in patent cases, as endorsed by the Appellate Division in Gentiruco, was followed in South Africa in a long line of decisions and was regarded as representing settled law until the judgment by Plewman JA in Ensign-Bickford (South Africa) (Pty) Ltd v AECI Explosives and Chemicals Ltd 1999 (1) SA 70 (SCA).

Without expressly overruling that part of the decision in the Gentiruco judgment pertaining to the admissibility of expert evidence, Plewman JA [at 81], in support of his contention that the emphasis must lie on the technical features when one determines obviousness, quoted a passage from Mölnlycke v Proctor and Gamble (5) [1994] RPC 49 (CA) at 113. In the quoted passage Sir Donald Nicholls VC said, inter alia, that ‘[t]he primary evidence will be that of properly qualified expert witnesses who will say whether or not in their opinions the relevant step would have been obvious to a skilled man having regard to the state of the art.’

This case reflects the modern English approach under s 125 of the English Patents Act of 1977 [See Cornish Intellectual Property 3rd ed (1996) par 3-56 at 117, and par 4-39 p 141 et seq.] and art 69 of the European Patent Convention. It does not reflect English law as at 30 May 1961, and is, of course, not binding on South African courts.

Burrell at 157 is of the view that the question now arises whether counsel may ask an expert witness his opinion as to whether a given step or alteration is obvious. His reading of the Ensign-Bickford case is that Plewman JA has impliedly overruled the approach in the Gentiruco case.

Burrell’s view was shared by MacArthur J in two subsequent judgments in the court of the Commissioner of Patents. In FIB Services South Africa v Glaverbel SA 2000 BIP 40 (CP), the judge said, with reference to Ensign-Bickford, that a person skilled in the art was required to advise the court whether ‘in his opinion the relevant step would have been obvious to a skilled man, having regard to the state of the art.’ Similarly, in Kerr‑McGee Chemical Corporation v Tioxide Group Services Ltd 1999 BIP 83 (CP) at 90, the learned judge said that he considered himself bound by the later decision - by Ensign-Bickford, not Gentiruco. The judge also referred to Hahlo and Kahn The South African Legal System and its Background (1968) at 253 footnote 38. The authors state in the text to this note that when ‘faced with two inconsistent Appellate Division decisions, probably a lower court would feel bound to follow the later one’.


An interpretation of the Ensign-Bickford case

I submit that Ensign-Bickford did not change our law in respect of the admissibility of expert evidence. While the unqualified approval of the dictum in the Mölnlycke case may create the incorrect impression and cause some doubt, Plewman JA clearly referred to this case not in support of a new approach to expert evidence, but rather in support of his contention that in determining obviousness the emphasis must be on the technical features of the product being considered. A careful analysis of Ensign-Bickford (South Africa) (Pty) Ltd v AECI Explosives and Chemicals Ltd at 80–81 makes this clear.

In his analysis of the claims, the learned judge of appeal referred to the part of the Gentiruco case containing the reference to the British Celanese case, without qualification and without indicating that he was actually in the process of overruling an important aspect of the earlier decision of the Appellate Division.

Plewman JA then evaluated the expert evidence under the heading of inventiveness. Reading this part of the judgment carefully, it does not say that the expert witnesses were expected to tell the court whether or not ‘in their opinions the relevant step would have been obvious to a skilled man having regard to the state of the art’. This also appears from the judge’s statement at 78 that the ‘only evidence relevant to the construction of the specification was that of Dr Viljoen who explained the nature and functioning of the patent and the meaning of technical words’. One must differentiate between the question whether a relevant step would have been obvious to a person skilled in the art, which is a question for the Court to decide upon all the evidence before it, and evidence explaining the nature and functioning of a patented product or process.

Had the Supreme Court of Appeal meant to overrule the seminal Gentiruco decision in this regard, it is submitted that the court would have done so expressly. That Plewman JA did not intend this result appears also from his judgment in Nampak Products Ltd v Man-Dirk (Pty) Ltd 1999 (3) SA 708 (SCA) at 712. In this judgment, delivered seven months after the judgment in Ensign-Bickford, Plewman JA said that, in determining the correct approach to the interpretation of a patent specification, ‘one need go no further than the careful examination of the problem’ in Gentiruco, with express reference to the very part of the judgment that contains the extensive quotation by Trollip JA from the British Celanese case. There is no indication in the Nampak judgment that Plewman JA regarded the Gentiruco case to have been overruled in this respect.

In Nampak, Plewman JA [at 712-4] actually sounded a note of caution to a court relying on modern English decisions on claim construction. He pointed out that art 69 of the European Patent Convention (EPC) of 1973 was an attempt to obtain some measure of uniformity in the construction of patent specifications in Europe. While the traditional British approach was as set out in the British Celanese case, the Continental approach relied heavily on the views of persons skilled in the relevant art. Article 69 aimed at achieving a balance between these two diametrically opposed approaches and found expression in s 125 of the English Patents Act of 1977, which reflected the intention of the European Patent Convention. Plewman JA said that a suggestion that extrinsic evidence as to the interpretation of patent specifications be led in all cases would not be in accordance with our law and would be contrary to the judgment of the Appellate Division in Gentiruco. He referred to the very part of the Gentiruco case containing the quotation from the British Celanese case.


Subsequent case law

The Ensign-Bickford decision was subsequently referred to in other cases  [Triomed (Pty) Ltd v Aktiebolaget Hässle & another 2001 BIP 84 (CP) and Aktiebolaget Hässle & Astrazeneca Pharmaceuticals (Pty) Ltd v Triomed (Pty) Ltd 2001 BIP 72 (CP)] but the impact of the decision on the law as set out in the Gentiruco judgement was not scrutinised.

The Supreme Court of Appeal had occasion to revisit the matter in Schlumberger Logelco Inc v Coflexip SA 2003 (1) SA 16 (SCA) par 33. Streicher JA said that the Court a quo [Coflexip SA v Schlumberger Logelco Incorporated 2001 BIP 1 (C).  Southwood J sat as the Court of the Commissioner of Patents] had held that, despite the misgivings expressed by Burrell, ’it must be accepted that the Supreme Court of Appeal was aware of the legal position and, despite the fact that the Court did not expressly overrule the previous judgements, it must have intended to change the law on this question.’ His Lordship then held[par 34] that the relevant ‘passage[at 81E-F] in the Ensign-Bickford case was not intended to be interpreted so as to change the law in respect of the admissibility of expert evidence in regard to the question of obviousness.’ This evidence was the technical evidence in respect of the nature of the (allegedly inventive) step, the state of the art, and the respect in which the step goes beyond the state of the art. His Lordship also pointed out that expert witnesses who give primary technical evidence would often arrive at a conclusion that the invention is obvious, or not, as the case may be, but these conclusions were harmless as long as it is borne in mind that the conclusions, as opposed to the technical evidence, were immaterial. The opinion of the expert as to obviousness was, and is, inadmissible.



It is not always easy to identify the ratio decidendi of a decision, or the extent to which it is inconsistent with previous decisions and thus overruled them. The judge sitting in the lower court is often called upon to decide that a precedent exists on the basis of ‘personal judgment’.[Hahlo & Kahn at 245-8 and 260.] A court is disinclined to pronounce its previous decision to be wrong. [See also Collett v Priest 1931 AD 290 at 297.; Bloemfontein Town Council v Richter 1938 AD 195 at 232.] Because of this reluctance to diverge from established principle, one would expect the Supreme Court of Appeal to consider the matter more carefully, and to give a more reasoned judgment when it wants to abandon long-held principles in favour of new ones. In short, had Plewman JA intended to abandon the principles adopted in Gentiruco, surely he would have told us why.

The stare decisis doctrine holds that, in the interest of certainty, a lower court is bound by a ratio decidendi of a court higher in a hierarchy, and a court does not easily diverge from its own previous rationes decidendi. [See Hahlo & Kahn at 214–301; Joubert (founding ed) The Law of South Africa vol 5 part 2 sv ‘Courts’ (by Van Dijkhorst) 1st reissue (by Preiss) (1994) at par 157–165 pp 114–117.] The ratio decidendi is the ‘rule of law the court considered was required for the decision of the case’. [Hahlo & Kahn at 261.] It must be distinguished from the obiter dicta. In Pretoria City Council v Levinson1949 (3) SA 305 (A) at 317, Schreiner JA stressed that uncertainties of definition created difficulties in differentiating between obiter dicta and rationes decidendi. After referring to various authorities he expressed himself as follows:

‘In this court in the case of Collett v Priest (1931 AD 290), De Villiers CJ says at p 302:

“. . . whatever the reasons for a decision may be, it is the principle to be extracted from the case, the ratio decidendi, which is binding and not necessarily the reasons given for it.”

It may be that the contrast between a reason and the ratio depends mainly on the meaning attached to those words in their context by the users. As I understand the ordinary usage in this connection, where a single judgment is in question, the reasons given in the judgment, properly interpreted, do constitute the ratio decidendi, originating or following a legal rule, provided (a)  that they do not appear from the judgment itself to have been merely subsidiary reasons for following the main principle or principles, (b) that they were not merely a course of reasoning on the facts [See Tidy v Battman 1934, L.J.K.B. 158.]. . . and (c) (which may cover (a)) that they were necessary for the decision, not in the sense that it could not have been reached along other lines, but in the sense that along the lines actually followed in the judgment the result would have been different but for the reasons.’


I submit that, at most, Plewman JA’s reference to the revised role of the expert witness in modern English law in Ensign-Bickford was merely a subsidiary reason for following a main principle (the judge’s contention that in determining obviousness the emphasis must be on the technical features), and that along the lines followed in the judgment the result would not have been different but for the reference to Mölnlycke v Proctor and Gamble (5) [1994] RPC 49 (CA). It follows that this reference does not constitute binding ratio decidendi.

The Ensign-Bickford case was decided in the Supreme Court of Appeal on the basis that the purported inventive step was obvious. [Ensign-Bickford (South Africa) (Pty) Ltd v AECI Explosives and Chemicals Ltd at 84.]In coming to this conclusion, the court did not rely on expert evidence that the invention was obvious. Rather, the court formed this opinion by itself. From what one may clean from the summary of their evidence in the report, not one of the witnesses testified that the invention was obvious. [See Ensign-Bickford (South Africa) (Pty) Ltd v AECI Explosives and Chemicals Ltd at 82 (in respect of Dr Viljoen) and 82–83 (in respect of Lundborg).]



The approach to the admissibility of expert evidence in the British Celanese case and endorsed by the Appellate Division (now the Supreme Court of Appeal) in Gentiruco still hold good in South Africa today. These principles have over the years enabled the courts to receive the opinions of experts without allowing these witnesses to usurp the function of the court.

While these well-established principles have served South Africa well should not be departed from lightly, the country can not afford to ignore the developments brought about by the harmonisation of patent laws in Europe. [See Cornish par 1-12 at 10, and par 3-01 at 91 et seq.] In Europe, harmonisation was dictated by the common denominators of the EPC and the Treaty of Rome. In South Africa, the need to be in step with major European trading partners is likely to lead to amendments to our patent legislation in order to bring about harmonisation with the European Union. The legislature should then look closely at the United Kingdom legislation and the EPC.

Also, we live in a World of ever-increasing sophistication and specialisation. It is to be expected that in future, judges will have to rely on expert evidence on matters involving technology more than ever before.

As always, it is necessary to strike a balance between maintaining the authority of the Court and making it possible for litigants to place relevant evidence before the Court.

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