Evidence of prior use was provided by witness testimony during ViCo oral proceedings at opposition. The Board of Appeal decision in T 423/22 related to the appeal of an opposition decision finding the patent ( EP220209) invalid for prior use. Rules 117 and 118 EPC were also amended to permit evidence in proceedings before the EPO to be taken by videoconference ( OJ EPO 2020, A135)

Most significantly was the introduction of new Article 15a of the Rules of Procedure of the Boards of Appeal (RPBA), according to which Boards of Appeal have the discretion to hold proceedings by ViCo whenever they consider it appropriate to do so ( IPKat). The EPO has also amended the rules of the EPC to explicitly allow the use of ViCo post-pandemic. Following a decision from the EPO President, ViCo is now the default form of oral proceedings before the opposition and examination Divisions ( IPKat). ViCo oral proceedings have persisted post-pandemic as a core component of the EPO's digital strategy. During the pandemic, the EPO introduced a ViCo oral proceedings pilot program, whereby all opposition and examining division oral proceedings were to be held by ViCo. The mandatory use of ViCo oral proceedings was introduced in response to the travel restrictions caused by the COVID-19 pandemic, which prevented most people from attending proceedings in-person at the EPO. Thus it is up to the relevant EPO division to decide whether the use of ViCo permits an adequate assessment. Importantly, the Board of Appeal also noted that it is the responsibility of the deciding division of the EPO to make a judgement about the witness's credibility. ViCo was therefore found to be a perfectly sufficient format for witness testimony, even when the entire outcome of a case rested on the witness evidence. The Board of Appeal concluded that body language is only ever a small part of an assessment of witness credibility.

The Board of Appeal in T 423/22 considered whether a witness's credibility can be adequately assessed when proceedings are conducted by video conference (ViCo).

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