Which national laws will UPC witnesses be subject to? And more "fun" questions from the draft UPC Code of Conduct

Sorry, what did you say, Merpel?  
The AmeriKat does not always listen to everything Merpel says and, indeed, even less often when Merpel tries to boss her around (which is frequently).  Nevertheless, it seems someone was listening to Merpel following her post on the CCBE's letter on the draft Code of Conduct for patent practitioners before the Unified Patent Court (see here).  Last week the Preparatory Committee published the current draft of the Code of Conduct (see here).  In the accompanying statement, the Preparatory Committee stated that:
"EPLAW, EPLIT and epi has taken on the task to help the Preparatory Committee develop a draft Code of Conduct for representatives who appear before the Court, as referred to in the Rules of Procedure of the Unified Patent Court. A draft Code of Conduct was presented to the Preparatory Committee at its 15th meeting on 14 of April 2016 where it was in general well received by delegations. Thereafter work has continued and the draft has been further improved. Further work is expected in the coming month before the draft is tabled again at the meeting of the Committee planned for 30 of June."
The Background section of the draft states that it is subject to any additional amendments of the Rules of Procedure.  It continues:
"Some observations in this respect were, however, made with regard to R. 291 (1) RoP while drafting the CoC. R. 291 (1) relates to the exclusion of representatives from the proceedings and, as presently drafted, would seem to compromise the position of both a Client and his/her Representative in ongoing litigation. 
Presently, until any possible future joint disciplinary body is founded, a mechanism for referring such a matter to a relevant body for the respective national lawyers or the epi would seem more appropriate. 
The draft CoC was discussed in the 3rd UPC Expert Panel Meeting in Paris on September 18th, 2015, where valuable feedback was received and thereafter incorporated. The draft Code of Conduct was presented to the full Preparatory Committee at its 15th meeting 14 of April 2016 where it met with general approval from Member States delegations. Furthermore, EPLAW, EPLIT and epi are grateful that experts in particular from IPLA and CCBE proposed amendments to the draft CoC in April and early May 2016, which are equally incorporated in the current version. All this was helpful to further improve the quality and acceptance of the CoC. In the coming weeks, EPLAW, EPLIT and epi will continue discussing the draft with interested parties."
The AmeriKat notes the reference to "under applicable law" in respect to witnesses of fact and party experts (adopted from the Rules).  For example, para 3.1. states:
"A Representative shall ensure that witnesses are at all times fully informed about their obligation to tell the truth and of their liability under applicable national law in the event of any breach of this obligation."
Under the Rules of Procedure, witnesses have a duty to tell the truth.  For example, Rule 175(2) provides that written witness statements shall be signed and include a statement of the witness that "he is aware of his obligation to tell the truth and of his liability under applicable national law in the event of any breach of this obligation.".  Rule 178(1)  provides that before the court hears witnesses, the witness needs to provide a declaration that the evidence they will give shall be the truth. Further, Rule 179(4) refers to the possible sanctions for giving false evidence as follows:
"The Court may decide to report to the competent authorities of the Contracting Member States whose courts have criminal jurisdiction in case of the giving of false evidence on the part of a witness." 
The same rules outlined above with respect to witnesses of fact also apply to experts.  Under Rule 181(2), experts are, when summoned under Rule 177, reminded that the they have a duty to:
  • assist the Court impartially on matters relevant to his area of expertise which overrides any duty to the party retaining him; and
  • be independent and objective, and shall not act as an advocate for any party to the proceedings.
Court appointed experts are subject to their own rules and duties (see Article 57 of the UPCA and Rules 185-189).

To the AmeriKat this immediately begs five questions:
  1. What applicable law is a witness governed by? In the case of experts, this should be relatively straightforward in that they may be governed by the terms of their engagement, but what about witnesses of fact? 
  2. Does paragraph 3.1 of the Code of Conduct mean that a representative has to actually substantively advise witnesses on their liability under applicable national laws (whatever that is)? Might such a requirement be in conflict with the representative's national code of conduct?   
  3. Will witnesses/experts involved in the same action, but subject to different national laws, create an uneven playing field in terms of evidence?  
  4. In relation to criminal offences, how does national criminal jurisdiction even pertain to the conduct of witnesses in the UPC?   
  5. How on earth is this going to work in practice?  

What a fun Monday afternoon research task for someone....Merpel?  Are you awake?  Do readers have any clever solutions?