prosecution history : CAFC Alert

Ramification of Silence in Prosecution History and Reminder on Formulating Effective Obviousness Arguments

| November 17, 2023


Decided: September 21, 2023

Before Reyna, Stoll, and Stark.  Opinion by Reyna.


The CAFC held that motivation to combine references is supported by substantial evidence including the patent prosecution history where relevancy of certain prior art, similar to an asserted reference in the IPR, was not contested by the applicant. The CAFC also rejected the patent owner’s arguments on lack of requisite findings on reasonable expectation of success, where such findings can be implied from express findings on motivation to combine as the two issues are interrelated to each other.


Elekta’s U.S. Patent No. 7,295,648 (the “’648 patent”) pertains to ionizing radiation treatment. The technology is designed to deliver therapeutic radiation, such as one created by a linear accelerator or “linac,” to a target area of a patient such as brain tumors for treatment purposes.  The ‘648 patent discloses that the linac, because of its great weight, requires a suitable structure to support the device while allowing a wide range of movement to focus the radiation precisely, leading to a challenge in implementing the linac-based system for treating highly sensitive, complex areas as with neurosurgery.

Representative claim 1 of the ‘648 patent recites:

A device for treating a patient with ionising radiation comprising:
a ring-shaped support, on which is provided a mount,
a radiation source attached to the mount;
the support being rotateable about an axis coincident with the centre of the ring;
the source being attached to the mount via a rotateable union having a an axis of rotation axis which is non-parallel to the support axis;
wherein the rotation axis of the mount passes through the support axis of the support and the radiation source is collimated so as to produce a beam which passes through the co-incidence of the rotation and support axes.

In the underlying inter partes review, the final written decision concluded, among other things, that claim 1 of the ’648 patent is obvious over a combination of Grady and Ruchala.  In essence, Grady teaches an X-ray imaging device having a sophisticated rotatable support structure similar to that recited in the body of claim 1, whereas Ruchala teaches a linac-based radiation device for treating tumors, which may correspond to “treating a patient with ionising radiation” of claim 1.

On appeal, the CAFC addressed Elekta’s three main arguments regarding obviousness of claim 1: (1) “the Board’s findings on a motivation to combine are unsupported by substantial evidence”; (2) “the Board failed to make any findings, explicit or implicit, on a reasonable expectation of success”; and (3) “even had the Board made such findings, those findings are not supported by substantial evidence.”  The CAFC reviewed the Board’s legal conclusions de novo and its factual findings for substantial evidence. 

  • Substantial evidence for the motivation to combine

Elekta argued that substantial evidence was lacking with the Board’s finding of a motivation to combine the references.  In particular, Elekta asserted that no motivation would have existed for a skilled artisan to combine Grady and Ruchala, one disclosing “radiation imagery” and the other for “radiation therapy,” where incorporating Ruchala’s linac radiation into Grady’s imaging system would not improve its imagery function in any aspect, whilst the linac’s heavy weight would hamper precision and control, thereby “render[ing] the device essentially inoperable.”

The Board’s obviousness conclusion relies on, among other findings, its review of the prosecution of the ’648 patent, wherein “patents directed to imaging devices were cited, and were not distinguished based on an argument that imaging devices were not relevant art,” along with the pertinent field being framed in the IPR as one that “includes the engineering design of sturdy mechanical apparatus[es] capable of rotationally manipulating heavy devices in three dimensions oriented in a variety of approach angles with high geometrical accuracy, in the context of the radiation imaging and radiation therapy environment.”

The CAFC held that there was substantial evidence for the motivation to combine. Specifically, the CAFC noted that such evidence includes the prosecution history of the ’648 patent, in which Elekta “notably did not argue that prior art references directed to imaging devices were not relevant art.”  The CAFC concluded that such failure to distinguish imaging radiation prior art during the patent prosecution, along with the asserted references and an expert testimony pointing to benefits of combining imagery and therapeutic radiation functions, substantially support the motivation to combine.

  • Findings on the reasonable expectation of success

Elekta argued that the Board’s obviousness determination was devoid of any findings on reasonable expectation of success.

The CAFC disagreed, finding that a sufficient, implicit finding was made as to the reasonable expectation of success.  The CAFC contrasted findings of reasonable expectation of success, which “can be implicit,” with those of motivation to combine, which must be “explicit.” Although an explicit finding would be usually required to support determinations made by the Board, the CAFC points to its precedent where the Board’s rejection of a patent owner’s motivation to combine argument based on teaching away constituted an implicit finding of a reasonable expectation of success, as the latter could be “reasonably discern[ed]” in the Board’s findings on “other, intertwined arguments.”

The CAFC noted that Elekta’s own arguments on the motivation to combine and the reasonable expectation of success presented before the Board were “blended”: Elekta essentially asserted that the suggested combination, lacking precision and control due to the device’s heavy weight, would fail to serve its intended purposes so as to negate motivation to combine, and consequently, would also negate reasonable expectation of success.  As such, the CAFC held that by making express findings on the motivation to combine, the Board adequately made an implicit finding on Elekta’s argument on reasonable expectation of success.

  • Substantial evidence for the reasonable expectation of success

Elekta argued that substantial evidence was lacking in the Board’s findings, if any, on reasonable expectation of success.

The CAFC succinctly rejected the argument. The CAFC noted that the evidence establishing a motivation to combine may—but not always—establish a finding of reasonable expectation of success.  And that was the case with the present appeal, where “the arguments and evidence of reasonable expectation of success are the same for motivation to combine.”


            This case presents an interesting situation pointing to one potential ramification of prosecution history made by silence: A failure to object to the scope of pertinent art during patent prosecution undercuts the patent owner’s argument in attacking the motivation to combine, where the asserted prior art is arguably from a disparate field.  It is important to consider potential benefits and downsides of presenting or not presenting certain arguments during prosecution.

            Another takeaway is the importance of formulating non-obviousness arguments on an issue-by-issue basis even if interrelated issues are involved; doing so would help keep the analysis of reasonable expectation of success from being comingled with the issues of motivation to combine.


| July 8, 2021

SpeedTrack, Inc. v., Inc. et al.

Decided on June 3, 2021

Prost (author), Bryson, and Reyna


The Federal Circuit affirmed the district court’s claim construction orders regarding the hierarchical limitations recited in the SpeedTrack’s ’360 patent based on Applicants’ arguments and claim amendments made during the prosecution of the ’360 patent. 


The ’360 patent

            SpeedTrack owns U.S. Patent No. 5,544,360 (“the ’360 patent), which is directed to providing “a computer filing system for accessing files and data according to user-designated criteria.”  The ’360 patent discusses that prior-art systems “employ a hierarchical filing structure” which could be very cumbersome when the number of files are large or file categories are not well-defined.  In addition, the ’360 patent discusses that some prior-art systems are subject to errors when search queries are mistyped and restricted by the field of each data element and the contents of each field. 

            However, the ’360 patent discloses a method that uses “hybrid” folders, which “contain those files whose content overlaps more than one physical directory,” for providing freedom from the restrictions caused by hierarchical and other computer filing systems.

            Representative claim 1 recites a three-step method: (1) creating a category description table containing category descriptions (having no predefined hierarchical relationship with such list or each other); (2) creating a file information directory as the category descriptions are associated with files; and (3) creating a search filter for searching for files using their associated category descriptions.

1.         A method for accessing files in a data storage system of a computer system having means for reading and writing data from the data storage system, displaying information, and accepting user input, the method comprising the steps of:

(a) initially creating in the computer system a category description table containing a plurality of category descriptions, each category description comprising a descriptive name, the category descriptions having no predefined hierarchical relationship with such list or each other;

(b) thereafter creating in the computer system a file information directory comprising at least one entry corresponding to a file on the data storage system, each entry comprising at least a unique file identifier for the corresponding file, and a set of category descriptions selected from the category description table; and

(c) thereafter creating in the computer system a search filter comprising a set of category descriptions, wherein for each category description in the search filter there is guaranteed to be at least one entry in the file information directory having a set of category descriptions matching the set of category descriptions of the search filter.

District Court

            In September of 2009, SpeedTrack sued retail website operations for infringement of the ’360 patent.  The Northern District construed the hierarchical limitation with the below construction (relied in part on disclaimers made during prosecution):

The category descriptions have no predefined hierarchical relationship. A hierarchical relationship is a relationship that pertains to hierarchy. A hierarchy is a structure in which components are ranked into levels of subordination; each component has zero, one, or more subordinates; and no component has more than one superordinate component.

            After that, SpeedTrack moved to clarify the district court’s construction regarding prosecution-history disclaimer.

            Subsequently, the district court issued a second claim construction order by adding the following clarification in its first order:

Category descriptions based on predefined hierarchical field-and-value relationships are disclaimed. “Predefined” means that a field is defined as a first step and a value associated with data files is entered into the field as a second step. “Hierarchical relationship” has the meaning stated above. A field and value are ranked into levels of subordination if the field is a higher-order description that restricts the possible meaning of the value, such that the value must refer to the field. To be hierarchical, each field must have zero, one, or more associated values, and each value must have at most one associated field.

            In order to support its second claim construction order, the district court analyzed SpeedTrack’s prosecution statements (for their clear disavowal of category descriptions based on hierarchical field-and-value relationships).

The Federal Circuit

            The CAFC handled the issue of claim construction.

            SpeedTrack acknowledged that the hierarchical limitation was added during the prosecution of the ’360 patent to overcome the Schwartz reference.

            During the prosecution, Applicants distinguished their invention from Schwartz by arguing that “unlike prior art hierarchical filing systems, the present invention does not require the 2-part hierarchical relationship between fields or attributes, and associated values for such fields or attributes.” 

In addition, Applicants argued that “the present invention is a non-hierarchical filing system that allows essentially ‘free-form’ association of category descriptions to files without regard to rigid definitions of distinct fields containing values.”

            Finally, Applicants argued that “this distinction has been clarified in the claims as amended by the addition of the following language in all of the claims: ‘each category description comprising a descriptive name, the category descriptions having no predefined hierarchical relationships with such list or each other.’”).

            The CAFC agreed with the district court’s assessment that predefined field-and-value relationships are excluded from the claims.

            The CAFC disagreed with SpeedTrack’s argument that the “category descriptions” of the ’360 patent are not the fields of Schwartz and that the hierarchical limitation precludes predefined hierarchical relationships only among category descriptions. 

            SpeedTrack argued that Applicants distinguished Schwartz on other grounds.  However, the CAFC did not agree with this argument. 

            In addition, the CAFC noted that SpeedTrack’s position contradicts its other litigation statements.  “Ultimately, the doctrine of prosecution disclaimer ensures that claims are not ‘construed one way in order to obtain their allowance and in a different way against accused infringers.’” Aylus Networks, Inc. v. Apple Inc., 856 F.3d 1353, 1360 (Fed. Cir. 2017) (quoting Southwall Techs., Inc. v. Cardinal IG Co., 54 F.3d 1570, 1576 (Fed. Cir. 1995)).

            Finally, the CAFC noted that both of the first and second construction orders acknowledged the disclaimer. 

            Therefore, the CAFC affirmed the district court’s final judgement of noninfringement.


  • Applicants need to be careful about claim amendments and arguments made during the prosecution of their patents.
  • Litigation statements, while not inventors’ prosecution statements and do not demonstrate prosecution-history disclaimer, can strengthen the court’s reasonings on the prosecution history. 

To read, or not to read an unrecited limitation into a patent claim, that is a question

| July 26, 2018

Blackbird Tech LLC v. ELB Electronics, Inc.

July 16, 2018

Before Prost, Moore and Reyna.  Opinion by Moore. Dissenting opinion by Reyna.


Finding no suggestion in the specification or prosecution history that the disputed unrecited limitation is important in any way that would merit reading it into the patent claim in dispute, the Federal Circuit vacated district court’s entry of judgment of noninfringement based on the contrary claim construction, and remanded the case to the district court for further proceedings. Dissenting opinion expressed totally opposite view on the issue, and affirmed the district court’s judgment.

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Even Without a Lexicography One Term May Have More Than One Meaning

| May 29, 2013

Title: Even Without a Lexicography One Term May Have More Than One Meaning

Author Name:  Bernadette K. McGann

Case Name:  Aventis Pharmaceuticals Inc. v. Amino Chemicals Ltd.

Key words:  Claim Construction, Intrinsic Evidence, Prosecution History

Decision Date: May 20, 2013

CAFC Panel and opinion author:  Newman, Bryson and Reyna.  Opinion by Reyna.  Dissenting opinion by Bryson


The claim in dispute recites a process of preparing a piperidine derivative compound that included providing a substantially pure regioisomer of a specific formula.  The District Court construed the meaning of “substantially pure” in relation to an intermediate compound to mean 98% purity, which is the same meaning as “substantially pure” when in relation to the piperidine derivative end product.  The CAFC reversed the “one construction throughout the patent” rule, adopted by the District Court.

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