Plaintiff Avoids Headache Of Having Its Thermometer Patent Invalidated At Summary Judgment

In a recent District of Massachusetts case, a defendant attempted to use the crucible of summary judgment to invalidate the plaintiff's body temperature detection patents. But, as shown in the Court's ruling, sometimes that strategy does not produce the desired results.

Plaintiff Exergen Corp., a manufacturer of human body thermometers, sued Defendant Kaz USA, Inc., alleging that Kaz's products infringe two of Exergen's temporal artery temperature detection patents. Kaz subsequently filed a motion for summary judgment of invalidity, arguing that Exergen's patents are invalid as obvious in view of the prior art—including Exergen's earlier '813 patent.

In its motion, Kaz contended that the '813 patent, which relates to measuring body temperature at the ear, teaches the key elements of the asserted claims and that Exergen was estopped from arguing otherwise based upon positions it took in an earlier litigation involving the '813 patent. In that earlier case, Exergen