The probative value of the declarations of a witness depends on the circumstances of the particular case (T 937/93). The credibility of witnesses cannot be impugned merely because they are related to one another and have a business relationship with one of the parties (T 363/90). An allegation based solely on suspicion cannot reasonably be expected to form a valid ground for casting doubt on the credibility of the evidence (see T 970/93 involving allegations of falsified evidence). Moreover, the fact that the statement was based on personal impressions of the witness could not be a reason to disregard it, because evidence is often based on the personal recollection of a person. If evidence based on personal impression were not credible per se, evidence from witnesses could never be credible (J 10/04). The statements of employees of one of the parties were regarded as sufficient evidence in a series of appeal cases, e.g. T 162/87 and T 627/88, T 124/88, T 482/89 (OJ 1992, 646), T 830/90 (OJ 1994, 713), T 838/92 and T 327/91.
In T 1191/97 the appellant's criticism of the evaluation of evidence by the department of first instance did not pose a serious threat to the witness's credibility. The fact that the events at issue had taken place a long time ago could readily explain certain imprecisions in the witness's testimony. The board saw no indication that the witness had been in breach of his obligation to testify to the best of his recollection.
In national proceedings before the Dutch District Court and Court of Appeal, several witnesses had been heard, and written statements had been introduced by both parties. The Dutch Court of Appeal could not establish an uninterrupted chain of proof that the alleged public prior uses had indeed taken place before the priority date of the contested patent. After evaluating the Dutch Appeal Court's findings, the board's judgment in T 665/95 was that no further investigations were necessary and that the conclusion of the Dutch Appeal Court could be followed, with the consequence that the subjectmatter of the granted claim 1, contrary to the impugned decision of the opposition division, was considered to be novel.