Of the above four elements needed for a preliminary injunction, “likelihood of success on the merits” will now be further considered. This is because it is perhaps the most important element for the plaintiff and the most difficult element to establish. In a patent infringement action, in order to prevail on the element of “likelihood of success on the merits,” the plaintiff must present a “clear showing.” This “clear showing” must establish the validity and enforceability of the patent and demonstrate that the accused device likely infringes at least one of the claims of the patent in suit, either literally or under the doctrine of equivalents. (See, for example, Atlas Powder Co. v. Ireco Chemicals, 773 F.2d 1230, 227 USPQ 289 (Fed. Cir. 1985)) In making this showing, the plaintiff must also defend against the accused infringer’s other patent defenses when such defenses raise a substantial question as to any of the elements.

A short discussion of what is required to prove patent infringement is in order. It has been long established that to evaluate patent infringement, a two-step inquiry must take place. First, the meaning of the patent claims must be properly construed. Then, the structure of the accused product must be compared with the claims to determine if the accused product contains each and every element of the properly construed claims. Southwall Technologies v. Cardinal IG Co., 54 F.3d 1570, 1575 (Fed. Cir. 1995).

In 1995, the Court of Appeals for the Federal Circuit (the appellate court created in 1982 to address, inter alia, cases arising out of the patent laws) ruled in the landmark case of Markman v. Westview Instruments, 52 F.3d 967, 34 U.S.P.Q.2d 1321 (Fed. Cir. 1995), aff’d, 517 U.S. 370 (1996). This case clarified the appropriate manner for courts to construe patent claims. In Markman, Supreme Court held that claim construction is a matter of law. As such, the meaning of claim terms is to be decided solely by the judge. In so deciding, the judge should consider the ordinary meaning of the claim terms to properly construe the claims, can consider intrinsic evidence such as the specification and file history (if made of evidence) if the ordinary meaning is ineffectual, or can consider extrinsic evidence as aids to his interpretation. The ruling in Markman has had, and continues to have, far-reaching effects on patent litigation and provides for an expeditious treatment of patent infringement cases.

Markman put an end to the excessive use of expert testimony on the issue of the meaning of claim language by holding that claim interpretation was exclusively a question of law, id. at 979, and that extrinsic evidence serves only a limited purpose – that of facilitating the judge’s understanding of the meaning of patent claim language. It is, of course, within the Court’s discretion whether to receive such extrinsic evidence. Id. at 981.

If the terms of the claims of the patent in suit are readily construed in accordance with their ordinary meanings and as they are used in the specification, there would be no need for what has been euphemistically termed a “ Markman hearing” for the Court to consider extrinsic evidence. Non-technical or non-scientific claim terms generally do not require extrinsic evidence to ascertain their meaning. Further, if upon examination of the intrinsic evidence – i.e., the claims, the specification, and the prosecution history – the meaning of the claim language is sufficiently clear, resorting to “extrinsic” evidence, such as treatises and technical references, as well as expert testimony when appropriate, should not be necessary. Digital Biometrics, Inc. v. Indentix Inc., 149 F.3d 1335, 1344, 47 USPQ2d 1418, 1424 (Fed. Cir. 1998). Thus, there would be no requirement to hold a time-consuming and expensive “ Markman hearing” when extrinsic evidence is not needed to ascertain the ordinary meaning of the claims.

As a plaintiff, it is often advantageous to convince the court that the claim terms are to be given their ordinary meaning and are easily understood, thereby eliminating the need for extrinsic evidence and a Markman hearing (and aiding in refuting allegations of non-compliance with 35 U.S.C. § 112). In any event, this determination of the meaning of the claim terms is the first step of determining patent infringement.

The second step is to apply the properly construed claims to the accused product. Generally speaking, this should be a rather simple task, for the structure of the accused product should be readily ascertainable by observation, without any significant disputes about that structure. For example, whether the component that is claimed as being “threaded” (as that term has been construed) is actually “threaded” in the accused device is easily answered by visually examining the accused product.

There are essentially two ways in which an accused product can infringe the claims of a patent: (1) through literal infringement and (2) through infringement under the doctrine of equivalents. Literal infringement, however, is seldom encountered in litigation and therefore the patent owner may well need to establish infringement under the doctrine of equivalents. If literal infringement exists and the accused infringer’s best defense is an obviousness argument, few infringers will have the temerity to litigate very long.

When the properly construed claims are applied to the accused device, in order to literally infringe a claim, each and every claimed element must be present in the accused device exactly. Laitram Corp. v. Rexnord, Inc., 939 F.2d 1533, 1535, 19 USPQ2d 1367, 1369 (Fed. Cir. 1991). As addressed above, literal infringement can usually be readily determined and, once established, the inquiry as to infringement need not progress any further. However, the more usual case is a determination of patent infringement under the doctrine of equivalents.

In order to infringe a claim under the doctrine of equivalents, the differences between the claimed element and the accused device must be “insubstantial.” Hilton Davis Chem. Co. v. Warner-Jenkinson Co., 62 F.3d 1512, 1517-18 (Fed. Cir. 1995). Courts have consistently held that in order for the accused product to infringe under the doctrine of equivalents, that product must perform substantially the same function in substantially the same way to produce substantially the same result. Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605, 608 (1950).

In evaluating any issue of equivalency, reference is made to the prosecution history to determine whether any amendments were made to the claims or arguments made by the applicant to overcome claim rejections and/or to obtain allowance of the claims, which would limit any equivalency assertions. This is called the doctrine of prosecution history estoppel and it precludes the patent owner from asserting an infringement position that had been surrendered in the Patent Office during prosecution.

In a recent case, Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki C., Ltd., 234 F.3d 558 (Fed. Cir. 2000), which has been argued before the United States Supreme Court and for which its decision is awaited, the Court of Appeals for the Federal Circuit held that voluntary claim amendments are treated the same as other claim amendments; therefore, any voluntary amendment that narrows the scope of a claim for a reason related to the statutory requirements for a patent will give rise to prosecution history estoppel with respect to the amended claim element. The Court further held that when a claim amendment creates prosecution history estoppel, no range of equivalents is available for the amended claim element. Id. at 563-64.

Issues of claim construction and equivalency, if necessary, will require the presentation of evidence as to the likelihood of success on the merits.

In order to prevail on a motion for preliminary injunction, the patent owner must demonstrate a probability of success on all of the merits. Thus, the patent owner must establish the validity of the patent and adequately defend against attacks by the accused infringer upon the validity of the claims of the patent in suit and upon the enforceability of those claims. For example, a patent is entitled to a presumption of validity and that presumption exists at every stage of the litigation, including during the preliminary injunction stage. However, where the accused infringer raises a “substantial question” as to the validity of the patent ( i.e. where the accused infringer presents evidence that he has a fair chance of success on the merits), the patent owner cannot merely rest on the presumption of validity. For example, in Helifix Ltd. v. Blok-lok Ltd. 208 F.3d 1339, 54 USPQ2d 1299 (2000), the Federal Circuit held that in order to resist the grant of a preliminary injunction, the defendant had to “raise a substantial question of patent invalidity”. Thus, even though the Federal Circuit held that the district court had erred in granting summary judgment to the defendants, it had not erred in denying a preliminary injunction to the plaintiff. The patent owner must establish that the defense lacks “substantial merit.” However, the court will not resolve the validity question in ruling on a preliminary injunction motion. Rather, the court must assess the persuasiveness of the evidence, recognizing that it is doing so without all evidence that may come out at trial. As such, the patent owner must address the validity issue when seeking a preliminary injunction, thereby consuming considerable time and effort.

When addressing the likelihood of success element involved in a motion for preliminary injunction, a wide variety of issues arise and can turn a motion for preliminary injunction into a mini trial on the merits.

The benefits of a preliminary injunction entered against the accused infringer are self-evident. However, there is a down side that must be considered. For example, the preparation of a motion for preliminary injunction is labor-intensive and expensive, requiring dedicated attorney time at an accelerated pace. The motion may be preceded by a motion for a Temporary Restraining Order (“TRO”) filed with the complaint. Such a motion addresses similar criteria for proofs as a preliminary injunction. This pleading is, in and of itself, labor intensive and is driven by the immediacy of the damage, so as to justify extraordinary relief granted on an extremely accelerated basis. Often, a TRO motion is filed ex parte, with little or no notice being given to the accused infringer.

If the TRO is denied, the litigation will return to the standard pace. While a preliminary injunction motion can still be presented, the denial of the TRO generally carries with it findings which will be detrimental to the success of a subsequent preliminary injunction motion. If the TRO is granted, the court will generally require a motion for preliminary injunction to be filed within a short period of time, often two weeks or less following the grant of the TRO. This accelerated pace of attorney work continues while the necessary papers are prepared.

As suggested above, the hearing on the motion for preliminary injunction can turn into a mini trial on the merits, with live testimony and, for all intents and purposes, full trial preparation which must be developed in short order and at a hectic pace. Because addressing the element of the probability of success also involves the establishment of patent validity, a wide variety of issues arise and thereby can, as is often the case, turn a motion for preliminary injunction into a mini trial on validity issues as well. To prepare for this in short order, activity is labor intensive on the part of counsel and expensive to the client.

If the motion for preliminary injunction is denied, which is the case more often than not, the litigation will return to the standard pace. However, if the preliminary injunction is granted, there is a requirement that the patent owner post a bond to protect against the possibility that the injunction was entered in error. Such a bond can be for a very large amount of money and can also be expensive for the patent owner to obtain and to maintain.