Priority. The right of an applicant to claim the filing date of his first application if, within 12 months, he files another application in respect of the same invention. At the Paris Convention back in 1883, all was set-up in order to help the inventor to protect his ideas. Fast-forward to nowadays, some practices within the EPO show that the priority claim may actually backfire on the patentee.
So how do priorities become toxic? The story begins with the common situation of further technical developments during the priority year, maybe even driven by new insights from the search report received somewhere during that priority year. Tricky situations arise when the later application EP2 claims for instance broader subjectmatter than was originally disclosed in the first application EP1. Just consider the following ‘AND claim’ situation: you have a first application disclosing features ‘A, B AND C’, what happens if in your subsequent application you claim ‘A, B, C AND D’? Or alternatively: first the invention was in a combination of ‘A and B’, and you later find that a claim on ‘A’ alone would suffice? In Europe, since G2/98 all is crystal clear: for such ‘AND claims’, you lose priority. Hands up. Any publications during the priority year could be used against you. (And you have the right to remain silent.) (But it is better not to.)
So far so good. But what if your first application gets published and still discloses embodiments within the scope of your claim?