In a growing trend, district courts are using their discretion to deny motions to stay patent infringement litigation in light of concurrent proceedings at the USPTO. In an earlier post, we commented on the Northern District of California’s deviation from that trend. In Advanced Analogic Technologies, Inc. v. Kinetic Technolgies, Inc., the concurrent proceeding was an inter partes reexam. In LG Electronics USA Inc. et al (“LG”) v. Whirlpool Corporation (“Whirlpool”) (Case No. 1-08-cv-00234), the defendant’s motion to stay was denied consistent with the trend to deny such motions and the concurrent proceeding was an interference. Judge Gregory M. Sleet of the District Court of Delaware denied Whirlpool’s motion to stay pending the outcome of an interference involving LG’s patents-in-suit. The patents-in-suit are patent Nos. 7,316,121 and 7,383,689 and relate to refrigerators, their compartments, and their components. In determining whether a stay is appropriate, a district court’s discretion is guided by the following factors: “(i) whether a stay would unduly prejudice or present a clear tactical disadvantage to the non-moving party; (ii) whether a stay will simplify the issues in question and trial of the case; and (iii) whether discovery is complete and whether a trial date has been set.” After considering those factors, Judge Sleet denied the motion to stay because (a) the interference might not resolve all issues regarding the asserted claims and (b) the litigation had progressed too far (i.e., discovery was complete and a trial date had been set). Unlike reexamination (which is substantially limited to prior art challenges), all grounds of unpatentability can be raised in an interference. That is, the Board of Patent Appeals and Interferences (“BPAI”) has discretion whether to authorize patentability challenges in an interference. Importantly, (1) the BPAI usually does authorize such challenges and (2) the decision whether to authorize a patentability challenge is made at a very early stage of an interference thus arming a district court judge with the information necessary to determine whether the interference is likely to simplify validity issues at trial. Interestingly, Judge Sleet was concerned that the concurrent interference would not simplify the validity issues. Interestingly, however, Judge Sleet’s Order does not indicate why he found that to be the case. It is also worth noting that most interferences are declared between a senior party applicant that provoked the interference and a junior party patentee. Accordingly, there is a high likelihood that, if the interference gets to the priority stage (which most do not), a senior party applicant (presumably Whirlpool) will obtain a judgment that the junior party patentee’s claims are unpatentable on the ground of priority. In contrast to requesting reexamination, requesting an interference can be a long and tortured ex parte examination process with the applicant largely at the mercy of an examiner who has little or no incentive to recommend an interference to the BPAI, and district courts will seldom stay an infringement litigation based merely on a suggestion of interference. Consequently, strategic use of a suggestion of an interference in support of a motion to stay an ongoing district court litigation is a risky proposition during the ex parte examination/suggestion process of the defendant’s pending application. The fact that the LG litigation had progressed as far as it had while Whirlpool attempted to provoke an interference is of little surprise.