Patents Act, 1970
25. Opposition to grant of patent
(1) At any time within four months from the date of advertisement of the acceptance of a complete specification under this Act (or within such further period not exceeding one month in the aggregate as the Controller may allow on application made to him in the prescribed manner before the expiry of the four months aforesaid) any person interested may give notice to the Controller of opposition to the grant of the patent on any of the following grounds, namely,-
(a) that the applicant for the patent or the person under or through whom he claims, wrongfully obtained the invention or any part thereof from him or from a person under or through whom he claims;
(b) that the invention so far as claimed in any claim of the complete specification has been published before the priority date of the claim-
(i) in any specification filed in pursuance of an application for a patent made in India on or after the 1st day of January, 1912; or
(ii) in India or elsewhere, in any other document:
PROVIDED that the ground specified in sub-clause (ii) shall not be available where such publication does not constitute an anticipation of the invention by virtue of sub-section (2) or sub-section (3) of section 29;
(c) that the invention so far as claimed in any claim of the complete specification is claimed in a claim of a complete specification published on or after the priority date of the applicant's claim and filed in pursuance of an application for a patent in India, being a claim of which the priority date is earlier than that of the applicant's claim;
(d) that the invention so far as claimed in any claim of the complete specification was publicly known or publicly used in India before the priority date of that claim.
Explanation: For the purposes of this clause, an invention relating to a process for which a patent is claimed shall be deemed to have been publicly known or publicly used in India before the priority date of the claim if a product made by that process had already been imported into India before that date except where such importation has been for the purpose of reasonable trial or experiment only;
(e) that the invention so far as claimed in any claim of the complete specification is obvious and clearly does not involve any inventive step, having regard to the matter published as mentioned in clause (b) or having regard to what was used in India before the priority date of the applicant's claim;
(f) that the subject of any claim of the complete specification is not an invention within the meaning of this Act, or is not patentable under this Act;
(g) that the complete specification does not sufficiently and clearly describe the invention or the method by which it is to be performed;
(h) that the applicant has failed to disclose to the Controller the information required by section 8 or has furnished the information which in any material particular was false to his knowledge;
(i) that in the case of a convention application, the application was not made within twelve months from the date of the first application for protection for the invention made in a convention country by the applicant or a person from whom he derives title, but on no other ground.
(2) Where any such notice of opposition is duly given, the Controller shall notify the applicant and shall give to the applicant and the opponent an opportunity to be heard before deciding the case.
(3) The grant of a patent shall not be refused on the ground stated in clause (c) of sub-section (1) if no patent has been granted in pursuance of the application mentioned in that clause; and for the purpose of any inquiry under clause (d) or clause (e) of that sub-section, no account shall be taken of any secret use.