0. Introduction and Overview
0.1 Priority entitlement is at the core of best patent practise, capable of determining “life and death” decisions in private patent validity disputes as well as in the more extreme of patent prosecution contexts. Whilst there is literature highlighting individual EPO Appeal Board decisions within this overall theatre, less than might be expected has been written on priority date assessment in the round using Enlarged Board of Appeal Decision G0002/98 as the starting point.
0.2 Priority is seldom a straightforward matter for patent proprietors where the technology concerned, or perhaps the proprietor’s understanding of it, grows within the priority year after first filing and leads to specification changes which threaten the originally established priority date.
0.3 Priority is equally a tough issue for tribunals and, as this paper will show, appellate decisions of the EPO have been an imperfect source of guidance for patent applicants and patentees. Indeed, a definitive position on multiple priorities is still lacking 15 years after the presidential referral which led to the landmark Enlarged BoardofAppealDecisionG0002/98. As one of a handful of concepts which are absolutely fundamental to the patent system, it is remarkable that any significant aspect of priority should still await final resolution after such a lengthy gestation period.
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