Art. 112a EPC was introduced with the EPC 2000, following a suggestion of the Enlarged Board of Appeal (G 1/97; OJ 2000, 322). Its purpose is not to make the Enlarged Board of Appeal a third instance (R 5/16: second judicial instance) but to provide for a limited judicial review of decisions of the boards of appeal. The grounds on which a petition for review can be based have been exhaustively defined by the legislator. These are, firstly, fundamental procedural defects which occurred in appeal proceedings and, secondly, the existence of a criminal act which may have had an impact on a decision (Art. 112a(2) EPC).

Art. 112a EPC expands on the right to a fair trial guaranteed by Art. 6 EHRC (R 9/14). The examples in Art. 112a(2)(a) to (c) EPC and particularly the wording of Art. 112a(2)(d) EPC make it clear that only fundamental (but not minor) procedural defects can be the basis for a petition for review (explanatory remarks in OJ SE 4/2007, 126; see also R 8/14). Review proceedings are confined to procedural defects so fundamental as to be intolerable for the legal system and overriding the principle that proceedings which have led to a final decision should not be re-opened in the interest of legal certainty (R 16/12, R 8/16). Art. 112a EPC provides an "exceptional means of redress" (R 1/08, R 2/12 of 17 October 2012 date: 2012-10-17, R 5/14, R 18/11, R 3/14; see also R 9/14), an "extraordinary legal remedy" (travaux préparatoires, MR/21/00; see also R 1/08, R 20/10, R 1/11, R 3/11), the provisions of which have to be applied strictly (R 1/08, R 23/10). A petition for review has no suspensive effect (Art. 112a(3) EPC).

From 13 December 2007 (the entry into force of Art. 112a EPC) to 31 March 2019, 164 decisions of the Enlarged Board on petitions for review (petitions withdrawn or deemed not to have been filed excluded) have been published on the Internet. In eight cases (R 7/09, R 3/10, R 15/11, R 21/11, R 16/13, R 2/14 of 22 April 2016 date: 2016-04-22, R 3/15, R 4/17) the decision under review was set aside and the appeal proceedings re-opened; the remaining petitions were rejected.