Art. 117(1)(g) EPC allows sworn statements in writing as a means of giving or obtaining evidence. Their purpose is to avoid the need to hear the undersigning person as a witness. Such declarations generally consist of answers to questions put forward by legal experts so that several declarations may have certain stereotyped formulations in common. With regard to evidence submitted in such statements, the board is not obliged to check the signatures as long as no counter-opinion has been presented concerning those signatures (T 674/91).
Sworn statements within the meaning of Art. 117(1)(g) EPC are the so-called "affidavits". The act of signing the affidavit and of swearing under oath that the statements it contains are true and correct to the best of the knowledge of the declarant, is done in the presence of a solicitor or a commissioner of oaths. Sworn statements in writing are not automatically ordered simply at the request of one of the parties. Like all means of giving or obtaining evidence listed in Art. 117 EPC 1973, the admissibility of such statements is subject to the discretion of the department concerned which has the power to order them only when considered necessary (T 798/93). In this regard, the board may consider an affidavit to be admissible evidence even if it is signed by the general manager of the appellant (see T 327/91).
Affidavits are to be distinguished from "statutory declarations", which are not given on oath. However, statutory declarations are solemn statements of evidence with the same effect as an oath and must equally be attested by a person authorised to administer oaths. Albeit not explicitly covered by Art. 117(1)(g) EPC, they are regarded as admissible means of evidence and are taken into account in accordance with the principle of the unfettered consideration of evidence (see e.g. T 770/91 and T 535/08).
The statutory declaration takes the place of the sworn statement in writing referred to in Art. 117 EPC (T 558/95). However, this type of statement is unknown in some national legal systems, which instead have their own instruments. For instance, statutory declarations are not one of the usual forms of evidence under the German law. Under this law, they are admissible only in particular cases and have a lesser probative value than a witness testimony. In proceedings before the EPO, however, even a simple declaration can be an admissible means of evidence within the meaning of Art. 117(1) EPC (T 474/04, OJ 2006, 129). Similarly, the EPO accepts unsworn solemn declarations the same way it accepts other unsworn statements (T 970/93, T 313/04).
In T 558/95 the board was unable to exclude the opponent's statutory declarations from the proceedings on the grounds that their wording was to some extent identical and that they had been drawn up by employees of the opponent. Whether or not the evidence provided was sufficient was a question of evaluation rather than a question of admissibility.