A patent can be considered invalid for failure to respond in good faith to an examiner's requisition. However, the June 2010 decision of the Federal Court in Weatherford Canada Ltd v Corlac Inc(1) may have clarified that the good-faith requirement does not apply in the absence of an examiner's requisition.

In earlier court decisions issued patents were deemed abandoned and thus considered invalid because the applicant did not reply in good faith to an examiner's requisition during prosecution. In GD Searle & Co v Novopharm Ltd(2) the Federal Court compared patent prosecution to an ex parte court proceeding, holding that a response was not made in good faith where the applicant presented arguments during prosecution which were inconsistent with an article published by the applicant that was not brought to the examiner's attention.

In Lundbeck Canada Inc v Ratiopharm Inc(3) the court held that an applicant's characterisation of 'the prior art' as "clearly [teaching] away" from a claimed combination was not a fair representation of the teachings of the prior art in view of a prior art reference, which was of record during prosecution and considered to be more relevant than the cited art. Therefore, the court held that the applicant's patent should be deemed abandoned.

The Federal Court revisited the good-faith requirement in Weatherford. While not necessarily a departure from the good-faith requirement set out in Searle and Lundbeck, the Weatherford decision at least provides an example of a factual scenario in which a patent was not deemed abandoned for a lack of good faith and could assist in clarifying the scope of the duty of good faith.

The patent at issue claimed a seal assembly combination designed to fix a problem of leaking stuffing boxes on rotary progressive cavity pumps used by heavy oil producers. The defendants challenged the validity of the plaintiff's patent on several grounds, including:

  • that the patent was anticipated and obvious in view of prior disclosures of the invention by the plaintiff that were not identified to the Patent Office during prosecution;
  • that the patent was void as a result of material mis-statements in the petition for patent, because the applicant had made a mis-statement regarding inventorship; and
  • that the patent should be deemed abandoned under Section 73 of the Patent Act because of the plaintiff's conduct cited by the defendant in respect of the grounds above.

Section 73 states that "an application for a patent in Canada shall be deemed to be abandoned if the applicant does not... reply in good faith to any requisition made by an Examiner in connection with an examination".


The defendant's various challenges to the validity of the patent were not successful.

The court held that the plaintiff's patent was not invalidated or deemed abandoned under Section 73. The court emphasised that Section 73 is "directed at controlling the prosecution of the patent process", and stated that "it would be stretching the meaning of s. 73 to read in a right to strike down a patent after it is issued on the basis of deemed abandonment during its prosecution unless all the constituent elements of s. 73 are met".

The court went on to hold that no duty of good faith arose under Section 73 in respect of the prior disclosures or the mis-statement about inventorship because there was no evidence that the examiner had issued any requisition in respect of prior art or inventorship during prosecution.

Thus, the Weatherford decision appears to limit the duty of good faith under Section 73 to issues relating to requisitions that the examiner has issued during prosecution. In other words, in the absence of an examiner's requisition, the duty of good faith based on Section 73 does not appear to extend to other provisions of the Patent Act.

The Weatherford decision is currently under appeal.


In view of Searle and Lundbeck, the cautious approach is for an applicant carefully to "state his or her own case fairly" and to inform the examiner "of any points of fact or law known to it" that are unfavourable to its position. It would be prudent to make of record any prior art of which the applicant is aware that is more relevant than what is before the examiner. While the Weatherford decision may clarify the scope of the good-faith requirement, it does not appear to warrant a departure from this approach.

For further information on this topic please contact Patrick Laycock at Smart & Biggar/Fetherstonhaugh by telephone (+1 613 232 2486), fax (+1 613 232 8440) or email ().


(1) 2010 FC 602.

(2) 2007 FC 81, rev'd on other grounds 2007 FCA 173.

(3) 2009 FC 1102.