T 0104/23 - (The limits on) Witness prepping at the EPO

Key points

• As I understand it, preparing your witness is fine in USA civil litigation, while UK law has a "fundamental prohibition, that “you must not rehearse, practise with or coach a witness in respect of their evidence" (source). What about the EPO?
• The present decision gives some guidance. 
• " the proprietor submits that the opponent spoke with the witness just before the witness was heard"
• "Contact between the opponent and witness during an interruption of oral proceedings may potentially raise doubts about the witness's impartiality and therefore diminish the probative value of their testimony. However, these are merely factors to consider when assessing the witness's credibility, especially considering the - undisputed - link between the witness and the opponent.  "
• "It would also appear as manifestly unrealistic to expect from parties to wholly refrain from contacting witnesses before their hearing, in particular to refrain from consulting them before a hearing. It is in the overall interest of the procedure that the witness statement is directed at those facts that are relevant to the case, and it is only natural that the attorney will have to talk to a witness before offering him or her as witness in the proceedings. Otherwise it would be plainly impossible for the attorney to select the appropriate persons, possibly out of a larger circle of people, very often all the employees of the party. "
  
  
  
  
• "The opposition division held, based on the witness testimony E1 together with evidence D4, D6 and D26, that the sale and delivery of the "LINCO Killing Machine Model IID" on 27 May 2009 (indicated as public prior use LINCO Benelux, Linco Benelux B.V., Linco Benelux or LINCO) constitutes state of the art (section 8 of the appealed decision). The appellant patent proprietor, in their grounds of appeal, challenges this finding of the division."
• "The appellant proprietor reiterates the same objections to admissibility of El and to the witness credibility as in first instance, namely the arguments that the opponent spoke with the witness just before the witness hearing, also pointing at the contradictions, lack of recollection and the unsolicited answers in the testimony."
• However, note that the evidence is actually: "the appellant proprietor argues that the admission and reliance on the witness testimony of Mr. [K] from the grandparent application (El) "
• As a comment, it is not clear to me if the members of the OD had a live interrogation of the witness in this case, and I doubt that written documents can be treated as 'witness evidence' in the sense of Article 117 EPC. 
• The proprietor could have requested a hearing of the witness and that document E1 be excluded as evidence if no witness hearing of Mr K took place before the OD in the case at hand.  
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• Separately, under Rule 103(4)(c), a statement that the appellant will not attend the oral proceedings was treated as a withdrawal of the request for oral proceedings, giving rise to a 25% refund of the appeal fee. 
• "The Board is aware that the case law does not appear to be uniform on this issue."  

EPO 

The link to the decision and an extract of it can be found after the jump.

https://www.epo.org/en/boards-of-appeal/decisions/t230104eu1