In Alberta v. Rambus, the CAND (J. Whyte, 8/10/07) refused to dismiss the interference counts in an infringement suit, because Resolution of the issue of an interference-in-fact requires more understanding of the technology, the state of the art at the relevant time and the level of ordinary skill in the art at that time. In essence, factual determinations that trump a rule 12(b) motion to dismiss.
Is interference-in-fact, a question of fact, or do claim construction and obviousness make the threshold inquiries matter of law? Presumably, an interference complaint will involve competing technology and similar products or processes. The Markman issues may directly answer whether the alleged interfering patents claim the same or substantially the same subject matter in similar form. Medichem v. Rolabo, (CAFC). As important are whether the claimed inventions are the same, as in PTO Rule 601(n), or patentably distinct, that is, non-obvious in view of the other.
Cases where a patentee sues for infringement, and defendant counterclaims with a similar patent, could more often provoke an interference count. That result is avoided due to (1) interference-in-fact being determined strictly by the claims, and not the spec, and (2) the two-way test. With the newly-wrought vagaries of KSR-style obviousness, the district court may be unable to rule on the jurisdictional issue of interference-in-fact until after a Markman decision and development of a record as to obviousness.