In J 3/88 the board noted that account should be taken of the fact that under Art. 134(1) EPC 1973 the contracting states had in principle confined representation of applicants before the EPO to "professional representatives" who, by virtue of their qualification should guarantee the best possible representation. The board stated that it followed that a representative could not relieve himself of responsibility for carrying out tasks which, by reason of his qualification, fell upon him personally, such as, for example, the interpretation of laws and treaties. If he delegated such tasks to an employee and if the latter made an error in the course of that work which resulted in the failure to observe a time limit, the representative could not claim that he had taken all due care required by the circumstances (see also J 33/90).
In J 31/89 the Legal Board of Appeal confirmed that erroneous interpretation of the EPC owing to a mistake of law on the part of the duly authorised representative with regard to the rules for calculating time limits (in the case in point, regarding the late payment of a renewal fee together with the additional fee) could not be excused. The appellant and the representative failed to determine correctly the last date for valid payment of the renewal fee (see J 42/89, T 853/90, T 493/95, T 881/98).
In T 624/96 the board expressed doubts about the nature of the original mistake, which concerned calculation of the time limit for filing the statement of grounds of appeal. This was possibly a "mistake of law" caused by ignorance or misinterpretation of the provisions of the EPC, as in e.g. J 31/89 or T 853/90. The board found that in the circumstances of the case at issue, however, the agent had not made a "mistake of law" of this kind. The agent cited an earlier appeal in which he had represented the same applicant, showing that he indeed had some familiarity with the appeals procedure. He also submitted programmes of training courses, at which he had given talks on European patents and EPO proceedings. It could be therefore be ruled out that a legal error in calculating the period for lodging the statement of grounds of appeal might have arisen from his ignorance of the EPC.
In J 28/92 the board held that the misinterpretation of a provision of the EPC by a representative was not without basis or unreasonable and considered that there was no basis for penalising the representative for having arrived at a not unreasonable interpretation of a rule of the EPC, which subsequently turned out to be wrong. The representative's interpretation of a legal provision of the EPC was not the result of, and did not lead to, a failure to exercise all due care required by the circumstances. In T 493/08 the board shared the view expressed in J 28/92 and stated that there might be exceptions to the rule that an error of law could not be excused, which, however, could be acknowledged only under rigorous criteria.
In T 516/91 the mistake made by the representative was that he requested an extension of two months for submitting the grounds of appeal. The board emphasised that the time limits set by Art. 108 EPC 1973 could not be extended. In mistakenly believing that an extension of these time limits was possible, the representative failed to exercise due care (see also T 248/91 and T 853/90).
Likewise, in T 460/95 the representative requested an extension of the time limit, although, in his professional capacity, he should have known that time limits under Art. 108 EPC 1973 could not be extended. The board noted that representatives were expected to be acquainted with the provisions of the EPC regarding time limits, and that the representatives in question had not been as vigilant as the situation demanded. In this specific case, however, the representative had taken the precaution of contacting the Registry of the Boards of Appeal beforehand, and had received information from that body which had led him to take action prejudicial to his interests. The board held that appellants should not suffer injury merely because they had relied on information received from the EPO which later proved to be mistaken or likely to have been misunderstood.
In T 881/98, the appellant's professional representative had written to the Registry of the boards of appeal requesting a two-month extension to a time limit, without giving reasons or indicating that the time limit in question was for submitting the statement of grounds of appeal. He added that if not notified to the contrary he would assume his request was allowed. The board refused the request for re-establishment. The Registry had not fallen short of legitimate expectations, as in this case (in contrast to T 460/95) the appellant had not been misled to his detriment by wrong information from the Registry but had himself made the mistake of thinking that the time limit could be extended.
In T 733/98 the board informed the appellants that the statement setting out the grounds of appeal did not comply with Art. 108, third sentence, EPC 1973. The appellants requested re-establishment in respect of the time limit for filing the statement of grounds, arguing that they had relied on Legal Advice No. 15/84 of the EPO, which had still been in force when they had received the communication under R. 51(4) EPC 1973. The board held that the appellants had misinterpreted the Legal Advice in question, having failed to realise that the procedure for handling main and auxiliary requests which it described no longer applied once amended R. 51 EPC 1973 entered into force. The board decided that the requirement of all due care required by the circumstances was not met in this case.