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England and Wales Court of Appeal (Civil Division) Decisions |
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You are here: BAILII >> Databases >> England and Wales Court of Appeal (Civil Division) Decisions >> Coflexip SA & aNOR v Stolt Offshore MS Ltd. & Ors [2003] EWCA Civ 296 (13 March 2003) URL: http://www.bailii.org/ew/cases/EWCA/Civ/2003/296.html Cite as: [2003] EWCA Civ 296 |
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COURT OF APPEAL (CIVIL DIVISION)
ON APPEAL FROM CHANCERY DIVISION
MR JUSTICE JACOB
Strand, London, WC2A 2LL | ||
B e f o r e :
LORD JUSTICE KAY
and
LORD JUSTICE JONATHAN PARKER
____________________
COFLEXIP SA COFLEXIP STENA OFFSHORE LIMITED | Claimants | |
- and - | ||
STOLT OFFSHORE MS LIMITED (Previously STOLT COMEX SEAWAY MS LIMITED) STOLT OFFSHORE LIMITED (Previously STOLT COMEX SEAWAY LIMITED) STOLT OFFSHORE A/S (Previously STOLT COMEX SEAWAY A/S) | Defendants |
____________________
Smith Bernal Wordwave Limited, 190 Fleet Street
London EC4A 2AG
Tel No: 020 7421 4040, Fax No: 020 7831 8838
Official Shorthand Writers to the Court)
Antony Watson QC, Colin Birss and Thomas Hinchliffe (instructed by Bird & Bird) for the Defendants
____________________
AS APPROVED BY THE COURT
Crown Copyright ©
Lord Justice Aldous:
"2. The Claimants contend that but for the Defendants' wrongful acts the First Claimant's appropriate UK operating subsidiary would have performed all or a proportion of those Infringing Contracts. Further if the First Claimant's appropriate UK operating subsidiary had performed the Infringing Contracts the Claimants would have made, in respect of each Infringing Contract, those profits which are referred to as lost profits in section B, and those uplifts and other amounts referred to hereunder in paragraphs 3, 4 and 5. The Claimants claim those lost profits and said uplifts and other amounts in respect of each of the Infringing Contracts.
The wrongful acts relied upon hereunder are
(a) In the case of Infringing Contracts (i), (ii), (iii) and (vi) the use of and offer for use of an infringing process as claimed in the Patent with the Vertical Lay System,
(b) In the case of all the Infringing Contracts the use of the Vertical Lay System which is an infringing product.
2A. In determining the proportion of Infringing Contracts which but for the Defendants wrongful acts would have been performed by the First Claimant's appropriate UK operating subsidiary the Claimants will, in addition to relying upon evidence relating to each of the individual Infringing Contracts, rely upon the loss of chance of performing the Infringing Contracts. In particular the Claimants rely upon those facts and matters pleaded in section F and that during the period 1995 31st July 2000 the Second Claimant's share of the UK flexible pipe installation market (excluding Infringing Contracts) was 60.8% and that during the period 1997 31st July 2000 the Second Claimant's share of the relevant UK rigid pipe installation market was 45%. The Claimants will contend that based upon this loss of chance the proportion (by value) of the Infringing Contracts which but for the Defendants said wrongful acts would have been performed by the First Claimant's appropriate UK operating subsidiary would have been (a) in the case of infringing flexible pipe installation contracts (contracts (i) to (vii), (xii), (xiv), (xv) not less than 60.8% and (b) in the case of those pipe installation contracts which included the laying of both flexible conduit and rigid pipe (contracts (viii) (x), (xiii)) not less than 45%.
3. Some of the prices set out in Section B were reduced due to the Defendants' infringing competition. Accordingly, where there has been such price reduction, the Claimants claim an uplift to the Section B losses as set out in Section C below.
Reasonable Royalty
7. In respect of that proportion of the Infringing Contracts for which the Claimants are not awarded damages for loss of profits, the Claimants will claim a royalty in respect thereof at a rate expressed against the particular contract value calculated by reference to 25% of the Defendants' anticipated incremental profit for the contract.
8. If, contrary to the First Claimant's contention set out in Section B below in respect of Magnus Swift, Magnus MP5/J2, Magnus J7, Foinaven and Dauntless/Durward, the First Claimant is not entitled to recover the loss of profit suffered by its operating subsidiary, then the Claimants will, in the alternative, claim a reasonable royalty in respect thereof.
Additional losses for Price Reduction (Non-Infringing Contracts)
9. The Claimants contend that but for the presence of the Defendants' Vertical Lay System in the market and the Claimants' belief that the Defendants were in direct competition with the First Claimant's appropriate UK operating subsidiary the said subsidiary would not have lowered its prices as particularised in tables 3 and 4 of the Confidential Schedule. The Claimants contend they are entitled to recover those losses arising from it lowering its prices as aforesaid together with an uplift to such losses in respect of variation in workscope as more particularly set out in Table 8 of the Confidential Schedule."
"It boils down to this, that in these extremely complicated and involved contracts which take a lot of negotiation, the claimants are not in a position to show that the use of the apparatus or process of the invention was considered crucial or indeed even material for either the defendants or their customers. So this is not a case like Gerber where there were really only two machines in the market -- plaintiffs' and the defendants' -- and it was the machines themselves which the customer wanted. It is not a case like The United Horse Shoe and Nail where it was the nails made by this process which the customer wanted. I infer from the report of that case that they were better than other nails, possibly because the process made better nails. This is a case in which it is alleged that the defendants used a particular method of laying the pipe. That, it is said, in itself entitles the claimants to say the competition damaged them by reason of the infringement. The say they are entitled to all the consequences of that competition. What is lacking, in my judgment, is any nexus between the patented invention and the contracts. Whether one puts it on the basis that all the contracts would have been obtained or that there was a chance that the contracts would have been obtained, I am of the view that the current pleadings make it impossible to proceed because they do not disclose any basis for deciding either one or the other or what the chance might have been.Mr. Miller submitted that the defendants here were simply, in effect, saying that they could have got the contracts by non-infringing means, as was contended by the defendants in The United Horse Shoe. Whilst at this level of court that proposition cannot be challenged, it seems to me that in any event this is different. In The United Horse Shoe it was the process which produced the nails which the public wanted: they were special nails. Here things are different: the customer was not interested in the process at all and it was not necessary to specify it to obtain the contract.
I think the appropriate thing to do is to give the claimants an opportunity to replead. Mr. Miller said there may be more information that he wants to put in. I was originally minded to strike it all out as it stands, but if he is going to replead, he will have to plead how and why the use of this invention was causative of the loss of prospect of each contract. That will depend upon the technology and not merely an assertion that the invention happened to be used in the course of the execution of the contract."
"As in the case of any other tort (leaving aside cases where exemplary damages can be given) the object of damages is to compensate for loss or injury. The general rule at any rate in relation to "economic" torts is that the measure of damages is to be, so far as possible, that sum of money which will put the injured party in the same position as he would have been in if he had not sustained the wrong. (Livingstone v. Rawyards Coal Co. 5 A.C. 25, 39, per Lord Blackburn.)
The respondent did not elect to claim an account of profits: their claim was only for damages. There are two essential principles in valuing that claim: first, that the plaintiffs have the burden of proving their loss: second, that the defendants being wrong-doers, damages should be liberally assessed but that the object is to compensate the plaintiffs and not punish the defendants. (Pneumatic Tyre Co. Ltd. v. Puncture Proof Pneumatic Tyre Co. Ltd. (1899) 16 R.P.C. 209 at p. 215).
These elemental principles have been applied in numerous cases of infringements of patents. Naturally their application varies from case to case. Reported authorities, many of which were cited in argument, may be useful as illustrations of judicial reasoning, but are capable of misleading if decisions on a particular set of facts and observations in judgments leading up to such decisions are later relied upon as establishing a rule of law. Nevertheless I think it useful to refer to some of the main groups of reported cases which exemplify the approaches of courts to typical situations.
1. Many patents of inventions belong to manufacturers, who exploit the invention to make articles or products which they sell at a profit. The benefit of the invention in such cases is realised through the sale of the article or product. In these cases, if the invention is infringed, the effect of the infringement will be to divert sales from the owner of the patent to the infringer. The measure of damages will then normally be the profit which would have been realised by the owner of the patent if the sales had been made by him (see The United Horse-Shoe and Nail Co. Ltd. v. John Stewart & Co., 13 A.C. 401.) An example of this is Boyd v. The Tootal Broadhurst Lee Co. (1894) 11 R.P.C. 175 where the plaintiff manufacturers proved that a profit of 7s. per spindle would have been made, and settlements of litigation for lesser rates were discarded.
Other patents of inventions are exploited through the granting of licences for royalty payments. In these cases, if an infringer uses the invention without a licence, the measure of the damages he must pay will be the sums which he would have paid by way of royalty if instead of acting illegally, he had acted legally.
In some cases it is not possible to prove either (as in 1.) that there is a normal rate of profit, or (as in 2.) that there is a normal, or established, licence royalty. Yet clearly damages must be assessed. In such cases it is for the plaintiff to adduce evidence which will guide the court. This evidence may consist of the practice, as regards royalty, in the relevant trade or in analogous trades; perhaps of expert opinion expressed in publications or in the witness box; possibly of the profitability of the invention; and any other factor on which the judge can decide the measure of loss. Since evidence of this kind is in its nature general and also probably hypothetical, it is unlikely to be of relevance, or if relevant of weight, in the face of the more concrete and direct type of evidence referred to under (2). But there is no rule of law which prevents the court, even when it has evidence of licensing practice, from taking these more general considerations into account. The ultimate process is one of judicial estimation of the available indications."
"If it could be shown that successful competition was only possible by using the waste saving invention, we admit that substantial damages might be recovered. But the evidence is that competition was due to other causes and not the infringement, and, therefore, only nominal damages are recoverable.
The second head of infringement is for an "interrupter", a contrivance to prevent clogging of the machinery at a particular stage. No interrupter was used in the making of several of the cases of nails. The interrupter had nothing to do with the sales. The evidence shows that the greatest fall in price took place at a time before the Defendant's competition would have affected it "
" The actual infringement complained of consists in the sale of cases of nails produced by patent machines, which are admitted to be infringements of the Pursuers' patents. Every nail thus produced was an infringement of the Pursuer's patents, the sale of which could have been interdicted, and would give a right of action against all concerned in its production and sale. The question appears to me to arise solely on the assessment of damages. But I think the admissions in this case render unnecessary, and, indeed, irrelevant, an examination into the various parts of the patents. The cases of nails tales quales were infringements, and in so far as these nails, such as they were, interfered with the sale of the Pursuer's own goods, they were properly the measure of the damages which the Pursuers were entitled to obtain. I say, so far as they interfered with the sale of the Pursuer's own goods, and while I agree with the Lord Ordinary that the Pursuers can only recover compensation for the actual loss which they have sustained, the estimate of the particular sum which is to be arrived at when assessing compensation for the injury is purely a matter for a jury, and can rarely be made the subject of exact arithmetical calculation.
I am satisfied, however, that the boxes and cases of nails sold by the Defenders did, in fact, interfere with the Pursuers' sale. I am unable to agree with Lord Adam that there is nothing in the proof to show, or make it probable that the Pursuers would have made these sales. I do not say all these sales. I think there is considerable evidence to show that purchasers generally would have sought that particular nail, and I do infer that the Pursuers, but for the intervention of the Defenders, would have effected a large part of these sale. And I certainly find from the evidence that among the competing nails in the market they were not all equally sought after, but that the Pursuers' nails had a higher reputation. I think it is nothing to the purpose to show, if it is shown, that the Defenders might have made nails equally good, and equally cheap, without infringing the Pursuers' patent at all. I will assume that to be proved, but if one assumes that the nails which were, in fact, made by the pirated machines injured the Pursuers' sales, what does it matter if it is ever so much established that the loss which the Pursuers have sustained by the unlawful act of the Defenders might also have been sustained by them under such circumstances as would give the Pursuers no right of action?
Your Lordships have to deal with the facts as they exist, and those facts, as I say, are that the Defenders have in derogation of the Pursuers' rights sold cases of nails which they have no right to sell, and for which to the extent to which they have interfered with the sale of the Pursuers' patented nails, the Pursuers are entitled to damages."
"The decision in the patent action and the minute of admission in the present case established beyond question that in selling the Shoe-brand nails the Respondents infringed the Appellants' rights. The sale of each and all of those nails was unlawful. It appears to be beside the mark to say that the Respondents might have arrived at the same result by lawful means, and that, without infringing the Appellants' rights, they might have produced a nail which would have proved an equally dangerous rival of the Globe nail. The sole question is, what was the loss sustained by the Appellants by reason of the unlawful sale of the Respondents' nails? There remains the other head of damage: loss of sales by reason of the competition of the Respondents. I think the Appellants are entitled to take into account the total quantity of nails sold by the Respondents, and that they are not limited, as the Lord Ordinary held they were, to the period commencing on the 27th of June 1883. Although that was the date on which the Appellants acquired their title to the patents, they succeeded to the rights and to the property of their predecessors in title. Then comes the question to what extent did the wrongful acts of the Respondents operate to prevent sales by the Appellants. I think it would be going too far to say that if the Respondents had not been in the field the Appellants would have sold an additional quantity equal to the amount sold by the Respondents. But considering that the Respondents seemed to have worked the ground occupied by the Appellants, and having regard to the progressive increase in sales during the previous years, and to the fact that the sales of the Appellants and of the Respondents taken together did not largely exceed the Appellants' sales in 1882, I think it is a fair inference that if the Appellants had been left undisturbed the natural increase of their business would have come near the aggregate of the quantity sold by the Appellants and Respondents together. If it were assumed that but for the interference of the Respondents, the Appellants would have sold 5752 boxes in addition to what they actually sold, their loss, taking the actual prices, would be £611. I think it would be reasonable to strike off from the amount a moderate percentage as representing sales due to increased activity protected by the rivalry of two competitors."
"It is not a case like United Horse Shoe and Nail where it was the nails made by the process which the customer wanted. I infer from the report of that case that they were better nails."
The judge gave no reason for that inference. The speech of Lord Macnaughton could not have formed a basis for that inference and a reading of the patents could well have led the judge to a contrary view. The patents were not directed towards producing better nails. They were directed at better processes which no doubt would provide cheaper and quicker production.
"Although the question whether and to what extent a plaintiff shall have sustained damage by reason of infringement is a question of fact assessed in the light of the broad principles mentioned above, certain methods of determining and assessing loss have been followed. One method is to ascertain whether the plaintiff has actually suffered a loss of sales which would otherwise have been made but for the competition of the infringing product. In cases where the patent holder has a monopoly of the product or its essential means of production, the issue is fairly readily answered since every sale of an infringing copy must have been at the expense of the monopoly. In a legally competitive market the plaintiff must show on the balance of probabilities that some sales have been lost by reason of the infringement, and the extent of such loss. Plainly such issues can be examined in only a general way, hence the frequent judicial observations about such matters being essentially jury issues. Naturally the difficulty of establishing loss does not relieve the plaintiff of the burden of proving loss. It is just that the matters for determination must necessarily be approached in a broad way which seeks to take account of all factors which may reasonably bear on the issue. In cases where the plaintiff cannot show an impact on its own sales by reason of infringement, it has not followed that the tortfeasor can be liable in only nominal damages. In such cases it has been held that the infringer can be liable in damages equivalent to a royalty. The justice of and commercial indications for such an approach are obvious."
"It is self evident that if the defendant had not infringed the plaintiff could not recover damages. The fact of the matter is that the defendant had infringed and it does not avail defendants to suggest that they might infringe with impunity because if they so wish they might compete lawfully."
"For the plaintiffs Mr. Bateson submitted that it would be consistent with the attitude of the law to an infringer for the law to assume that the plaintiffs would have made, with their patented lintels, those sales made by the defendants with the infringing lintels unless and in so far as the defendants proved the contrary. In a case such as this, where the plaintiffs had been established for a number of years as the market leaders with their patented construction, having available ample production capacity and stocks (except for the temporary steel strike shortage in one part of their range to which I have referred), but never having granted any licence under their patent, and where defendants not previously in business in this field at all, entered the market with the object of doing so at the expense of the plaintiffs and using an infringing version of the plaintiffs' patented construction, in my judgment that is a proper approach for the court to adopt. (See Lord Wilberforce's first group of cases in the passage I have cited from the General Tire case.) Mr. Bateson accepted that if an infringer could show that his customer would have dealt with a lawful competitor of the plaintiffs that would have the effect of reducing the number of sales in respect of which the plaintiffs could claim loss of profit. I would just add to that that a defendant infringer might be able to establish that a plaintiff patentee would not have made an infringing sale for some other reason.
The defendants contended that the plaintiffs have failed completely to prove their case that they have suffered damage through loss of profits. This contention was based on two arguments as I understand it, namely,
(i) if the defendants had not made and sold infringing lintels they would have made and sold non-infringing lintels and retained their share of the market; (ii) if the defendants had not supplied their customers with lintels, lintels other than the plaintiffs' lintels would have been bought by the customers, i.e. lintels of other competitors of the plaintiffs.
I have to say at once, that in my judgment the first of those arguments (i.e. argument (I)) is not open to the defendants in law: see principle (d) above. The United Horse Shoe and Nail Company Limited casesee especially the passages I have already cited from the speeches in the House of Lordsis authority for the proposition that an infringer is barred from defeating a plaintiff patentee's claim for damages for loss of profits by saying: "Yes, I infringed but I could have taken this market from you by not infringing." Much of Mr. Gratwick's address on the "loss of profits" part of the claim was devoted to, and much of the defendants' evidence directed to, this argument, but as in my view the argument is wrong in law the evidence directed to it is irrelevant and I need not consider it further."
"Infringement of a patent is a statutory tort; and in the ordinary way one would expect the damages recoverable to be governed by the same rules as with many or most other torts. We were referred to Halsbury's Laws of England (4th edn) vol. 12 para 1128 and following, to establish the elementary rules (i) that the overriding principle is that the victim should be restored to the position he would have been in if no wrong had been done, and (2) that the victim can recover loss which was (i) foreseeable, (ii) caused by the wrong, and (iii) not excluded from recovery by public or social policy. The requirement of causation is sometimes confused with foreseeability, which is remoteness. The two are different - see Halsbury para 1141:
"1141. Causation in tort. Subject to foreseeability and the principles of public policy it is prima facie necessary and sufficient for a plaintiff to prove that a defendant's wrongdoing was a cause and not necessarily the sole or dominant cause of his injuries, as a matter of physical consequences or common sense, but subsidiary principles associating foreseeability and causation have been evolved in certain categories of concurrent or intervening causes."
It is not enough that the loss would not have occurred but for the tort; the tort must (for present purposes at any rate) be, as a matter of common sense, a cause of the loss.
There is no dispute about foreseeability or causation in the present case. It is conceded that both requirements (if there are two) are satisfied. What is said is that either the general rules in Halsbury do not apply to the Patents Act, or else there is now a fourth limitation which must be satisfied.That fourth limit is to be derived from the speech of Lord Hoffmann in South Australia Asset Management Corporation v. York Montague Ltd. [1996] 3 WLR 87 (aka the Banque Bruxelles case) at pages 92-l94:
"Much of the discussion, both in the judgment of the Court of Appeal and in argument at the Bar, has assumed that the case is about the correct measure of damages for the loss which the lender has suffered.
I think that this was the wrong place to begin. Before one can consider the principle on which one should calculate the damages to which a plaintiff is entitled as compensation for loss, it is necessary to decide for what kind of loss he is entitled to compensation. A correct description of the loss for which the valuer is liable must precede any consideration of the measure of damages. For this purpose it is better to begin at the beginning and consider the lender's cause of action.
In the present case, there is no dispute that the duty was owed to the lenders. The real question in this case is the kind of loss in respect of which the duty was owed.
How is the scope of the duty determined? In the case of a statutory duty, the question is answered by deducing the purpose of the duty from the language and context of the statute: Gorris v. Scott (1874) L.R. 9 Ex. 125. In the case of tort, it will similarly depend upon the purpose of the rule imposing the duty.
Rules which make the wrongdoer liable for all the consequences of his wrongful conduct are exceptional and need to be justified by some special policy. Normally the law limits liability to those consequences which are attributable to that which made the act wrongful. In the case of liability in negligence for providing inaccurate information, this would mean liability for the consequences of the information being inaccurate.""
"69. How, then, does one identify a plaintiff's "true loss' in cases of tort? This question has generated a vast amount of legal literature. I take as my starting point the commonly accepted approach that the extent of a defendant's liability for the plaintiff's loss calls for a twofold inquiry: whether the wrongful conduct causally contributed to the loss and, if it did, what is the extent of the loss for which the defendant ought to be held liable. The first of these enquiries, widely undertaken as a simple "but for' test, is predominantly a factual inquiry. The application of this test in cases of conversion is the matter now under consideration. I shall return to this in a moment.
70. The second inquiry, although this is not always openly acknowledged by the courts, involves a value judgment ("ought to be held liable..'). Written large, the second inquiry concerns the extent of the loss for which the defendant ought fairly or reasonably or justly to be held liable (the epithets are interchangeable). To adapt the language of Jane Stapleton in her article "Unpacking ""Causation" ' in Cane and Gardner (ed) Relating to Responsibility (2001), page 168, the inquiry is whether the plaintiff's harm or loss should be within the scope of the defendant's liability, given the reasons why the law has recognised the cause of action in question. The law has to set a limit to the causally connected losses for which a defendant is to be held responsible. In the ordinary language of lawyers, losses outside the limit may bear one of several labels. They may be described as too remote because the wrongful conduct was not a substantial or proximate cause, or because the loss was the product of an intervening cause. The defendant's responsibility may be excluded because the plaintiff failed to mitigate his loss. Familiar principles, such as foreseeability, assist in promoting some consistency of general approach. These are guidelines, some more helpful than others, but they are never more than this.
71. In most cases, how far the responsibility of the defendant ought fairly to extend evokes an immediate intuitive response. This is informed common sense by another name. Usually, there is no difficulty in selecting, from the sequence of events leading to the plaintiff's loss, the happening which should be regarded as the cause of the loss for the purpose of allocating responsibility. In other cases, when the outcome of the second inquiry is not obvious, it is of crucial importance to identify the purpose of the relevant cause of action and the nature and scope of the defendant's obligation in the particular circumstances. What was the ambit of the defendant's duty? In respect of what risks or damage does the law seek to afford protection by means of the particular tort? Recent decisions of this House have highlighted the point. When evaluating the extent of the losses for which a negligent valuer should be responsible the scope of the valuer's duty must first be identified: see Banque Bruxelles Lambert SA v Eagle Star Insurance Co Ltd [1997] AC 191. In Reeves v Commissioner of Police of the Metropolis [2000] 1 AC 360 the free, deliberate and informed act of a human being, there committing suicide, did not negative responsibility to his dependants when the defendant's duty was to guard against that very act.
72. The need to have in mind the purpose of the relevant cause of action is not confined to the second, evaluative stage of the twofold inquiry. It may also arise at the earlier stage of the "but for' test, to which I now return. This guideline principle is concerned to identify and exclude losses lacking a causal connection with the wrongful conduct. Expressed in its simplest form, the principle poses the question whether the plaintiff would have suffered the loss without ("but for') the defendant's wrongdoing. If he would not, the wrongful conduct was a cause of the loss. If the loss would have arisen even without the defendant's wrongdoing, normally it does not give rise to legal liability. In Barnett v Chelsea and Kensington Hospital Management Committee [1969] 1 QB 428 the night watchman's death did not pass this test. He would have died from arsenic poisoning even if the hospital casualty department had treated him properly. Of course, even if the plaintiff's loss passes this exclusionary threshold test, it by no means follows that the defendant should be legally responsible for the loss.
73. This threshold "but for' test is based on the presence or absence of one particular type of causal connection: whether the wrongful conduct was a necessary condition of the occurrence of the harm or loss. In the Barnett case the hospital's negligence was not a necessary element in the conditions which led to the watchman's death. He would have died anyway. In very many cases this test operates satisfactorily, but it is not always a reliable guide. Academic writers have drawn attention to its limitations: see, for example, the late Professor Fleming's The Law of Torts, 9th ed (1998), pp 222-230, and Markesinis & Deacon Tort Law, 4th ed (1999), pp 178-191. Torts cover a wide field and may be committed in an infinite variety of situations. Even the sophisticated variants of the "but for' test cannot be expected to set out a formula whose mechanical application will provide infallible threshold guidance on causal connection for every tort in every circumstance. In particular, the "but for' test can be over-exclusionary."
"To obtain as damages the profits on sales he would have made absent the infringement, i.e., the sales made by the infringer, a patent owner must prove: (1) demand for the patented product, (2) absence of acceptable noninfringing substitutes, (3) his manufacturing and marketing capability to exploit the demand, and (4) the amount of the profit he would have made."
Lord Justice Kay:
Lord Justice Jonathan Parker:
"There is therefore no uniform causal requirement for liability in tort. Instead, there are varying causal requirements, depending upon the basis and purpose of liability. One cannot separate questions of liability from questions of causation. They are inextricably connected. One is never simply liable: one is always liable for something and the rules which determine what one is liable for are as much part of the substantive law as the rules which determine which acts give rise to liability. It is often said that causation is a question of fact. So it is, but so is the question of liability. Liability involves applying the rules which determine whether an act is tortious to the facts of the case. Likewise, the question of causation is decided by applying the rules which lay down the causal requirements for that form of liability to the facts of the case."