Technical article

Experts in CE and product safety processes: "If you say too much, you're out".

Why a judicial expert in a machinery defect case may not point out missing CE marking, EC Declaration of Conformity and German operating instructions

 What is it about?

  • Rejection of an expert due to concern of bias
  • Parties to the proceedings rule over the subject matter of the proceedings (principle of party rule)
  • Court experts may only comment on the "facts in dispute" and may not go beyond the evidentiary topic (prohibition of exceeding the mandate)
  • If the subject of proof is "material" technical equipment defects and operating errors, the violation of formal obligations according to the EC Machinery Directive is not relevant.
  • Mistrust of impartiality in case of indication of missing documents according to EC Machinery Directive, if their absence had not been objected to so far



In a civil law warranty case concerning material defects of a 3D printer, the buyer and the seller dispute whether the device was already defective at the time of the transfer of risk or whether it was operated incorrectly. Dr S, the expert appointed to clarify this issue, informed the court that, contrary to the provisions of the European Machinery Directive 2006/42/EC, the printer had an instruction manual in English instead of German and "it was not clear from the file whether the mandatory EC Declaration of Conformity was present and whether the CE mark was clearly visible". Dr. S suggested adding to the evidence decision whether "the requirements of the 9th Product Safety Regulation (ProdSV) had been taken into account and complied with by the supplier when the machine was handed over".



The seller objected to Dr. S on the grounds of bias according to § 406 in conjunction with § 42 ZPO (Code of Civil Procedure), but the Regional Court of Dessau rejected this1 : "In principle, the expert is obliged to comprehensively examine the facts of the case from his expert point of view and to give corresponding professionally justified advice on the clear formulation of the subject matter of the evidence". Here, "the object of the expert opinion is to determine whether the complaints made by the buyer are based on technical defects of the machine or are due to operating and maintenance errors. This also includes determining whether the buyer had access to a German instruction manual“.

The Naumburg Higher Regional Court (OLG) overturns the decision of the Dessau Regional Court at2 - and first says in principle: "For a rejection due to concern of bias, it does not depend on whether the expert is actually biased or considers himself to be biased or whether the court has doubts about his impartiality. Rather, it is sufficient that there are sufficient reasons which, in the eyes of a reasonable party, are likely to raise doubts about the impartiality of the expert".

Here, "an apprehension of bias against the expert Dr. S. is justified" because of the "appearance of not being completely impartial". With his suggestion to supplement the evidence order, he "made himself the lawyer of the buyer from the point of view of the seller. However, according to the content of the evidence order, until this suggestion the parties were not in dispute as to whether the seller could have committed a breach of duty in this respect when delivering the printer. Rather, according to the content of the order to take evidence, the only issue so far is whether there was an initial defect when the printer was delivered or whether defects were only caused by operating errors on the part of the buyer". The suggestion concerned "a breach of duty on the part of the seller which had obviously not been alleged by the buyer up to that point. Dr. S thus suggested that the buyer could base a possible operating error on the lack of a German-language instruction manual. Evidence is always to be taken by the court, however, only in compliance with the burden of presentation and proof regarding disputed factual assertions of the parties, insofar as they are decisive for the dispute. Pursuant to section 139 of the Code of Civil Procedure, the court is also obliged to discuss and ask questions. However, this is limited by the principle of the parties' control over the subject matter of the proceedings, which must be observed at all times. An expert witness, just like a judge, may not work towards a party basing its procedural goal on a different factual submission".

The OLG ends linguistically very elegantly: What Dr S suggested is "not a professionally justified suggestion for a more lucid formulation3 of a disputed evidence topic", but "violates the required equidistance to the parties4 ".



1. The Federal Supreme Court summarises: "The fear of a lack of impartiality may be justified if the expert completes the expert's assignment in such a way that it can be interpreted as an expression of an unobjective basic attitude towards a party. Such an unobjective basic attitude may result from the expert taking measures that are not covered by his or her expert assignment. Thus, the apprehension of bias of the expert from the point of view of a party has been assessed as justified if the expert, in his expert opinion exceeding the limits of his mandate, has shown the litigants the way to decide the legal dispute which he considers to be correct"5 . Dr. S put the buyer on notice that the lack of a German-language instruction manual alone was a defect.

2. Incidentally, the fact that a missing instruction manual is a material defect has been regulated by the new § 434 para. 3 no. 4 BGB since 1 January 2022 thus: "Unless otherwise effectively agreed, the item complies with the objective requirements if it is handed over with the accessories, including the packaging, the assembly or installation instructions and other instructions that the buyer can expect to receive". And in the case of machinery, one can expect German operating instructions in Germany, because according to Art. 5 (1) c) in conjunction with. Annex I No. 1.7.4 of the Machinery Directive.

3. If the subject of the evidence was whether "defects were caused by faulty operation", the comprehensibility and thus the language of an instruction manual can also be relevant6. The expert should therefore not have suggested supplementing the evidence order, but could simply have examined this question and reported the result on this7.

4. The Dessau Regional Court added that the consequences of a possibly missing declaration of conformity and CE marking "are not facts relevant to the decision". The Regional Court Erfurt considers this to be incorrect and held that a wheel loader without CE and declaration of conformity was defective because it "does not have a valid operating permit because not all requirements of the Machinery Directive are fulfilled"8 . If the court followed this and considered the printer to be defective for this reason alone, it would have to point this out to the parties to the proceedings in accordance with § 139 (2) ZPO. The OLG Düsseldorf, on the other hand, is of the opinion: The lack of a CE marking is not itself a defect9.

Regional Court Dessau-Roßlau, order dated 18.10.2013 (Ref. 3 O 40/13).
2Higher Regional Court Naumburg, order dated 28.11.2013 (ref. 10 W 66/13).
3 From Latin lucidus = "full of light, bright", i.e. "to present clearly and comprehensibly".
4Equidistance in politics means: "equal ideological distance from other political actors".
5 BGH, Beschluss v. 11.04.2013 (Az. VII ZB 32/12).
6In detail Wilrich, Produktsicherheitsrecht und CE-Konformität - Hersteller-, Importeur- und Händler Pflichten für Technik- und Verbraucherprodukte bei Risik Assessment, Konstruktion, Warnhinweisen und Vertrieb, 2021.
7For the tasks and responsibilities of service managers and inspectors, see Wilrich, Technik-Verantwortung - Sicherheitspflichten der Ingenieure, Meister und Fachkräfte und Organisation und Aufsicht durch Management und Führungskräfte, 2022.
8Regional Court Erfurt, judgement from. 07.08.2014 (Az. 10 O 410/12) - case review in Wilrich, Sicherheitstechnik und Maschinenunfälle vor Gericht - 40 Urteilsanalysen zu Produktsicherheit, Hersteller- und Konstruktionspflichten, Arbeitsschutz, Betreiber- und Organisationspflichten, 2022.
9Higher Regional Court Düsseldorf, judgement from. 16.04.2020 (ref. 5 U 131/18) - on a construction product.


Annex: Extract from the Code of Civil Procedure (ZPO) - Translated into English

§ 42 Recusal of a judge from a case
(1) A judge may be recused from a case both in those cases in which he is disqualified by law from exercising a judicial office, and in those cases in which there is a fear of bias.

(2) A judge will be recused for fear of bias if sound reasons justify a lack of confidence in his impartiality.

(3) In all cases, both parties shall have the right to recuse a judge.

§ 139 Direction in substance of the course of proceedings
(1) To the extent required, the court is to discuss with the parties the circumstances and facts as well as the relationship of the parties to the dispute, both in terms of the factual aspects of the matter and of its legal ramifications, and it is to ask questions. The court is to work towards ensuring that the parties to the dispute make declarations in due time and completely, regarding all significant facts, and in particular is to ensure that the parties amend by further information those facts that they have asserted …

(2) The court may base its decision on an aspect that a party has recognisably overlooked or has deemed to be insignificant, provided that this does not merely concern an ancillary claim, only if it has given corresponding notice of this fact and has allowed the opportunity to address the matter. …

§ 359 Content of the evidence warrant
The order for evidence to be taken shall: 1. Designate the facts at issue, regarding which evidence is to be taken; ...

§ 406 Refusal of an expert
(1) An expert may be rejected for the same reasons for which a party is entitled to challenge a judge.

Posted on: 2022-08-09


Prof. Dr. Thomas Wilrich
Active around the topics of product safety, product liability, occupational health and safety and distribution of goods including the corresponding company organisation, contract drafting, damages and executive liability, insurance issues and criminal defence. He is responsible for business, labour, technical and corporate organisation law as well as "Law for Engineers" at the Faculty of Industrial Engineering at Munich University of Applied Sciences.


Email: |


You are not yet registered? Register now for the free CE InfoService and receive information by e-mail when new technical papers, important standards publications or other news from the field of machinery and electrical equipment safety or product compliance are available.


Picture advertisement seminar efficient CE marking and risk assessment of machines and plants

Support by IBF

CE Software Safexpert

CE software for systematic and professional safety engineering


Practical seminars on aspects of risk assessment and ce-marking

Stay Up-to-Date!

With the CE InfoService you stay informed about important developments in the field of product safety.