U.S. Patent No. 8,639,838, directed to messaging.  The district court indicated that filing a terminal disclaimer resulted in claim preclusion, relying on non-infringement of the parent patent with the understanding that the terminal disclaimer indicated that the continuation patent was to the same dispute.  According to the Federal Circuit, “a terminal disclaimer is a strong clue that a patent examiner and, by concession, the applicant, thought the claims in the continuation lacked a patentable distinction over the parent.  But as our precedent indicates, that strong clue does not give rise to a presumption that a patent subject to a terminal disclaimer is patentably indistinct from its parent patents.” (page 12).  Thus, the district court should have compared claims (page 12).

Hindsight: A terminal disclaimer may be filed for various reasons, even when the claims are patentably distinct.  When filing a terminal disclaimer, it may be beneficial to state any reason for filing the disclaimer where that reason is other than overcoming the claims of the related patent.  One example may be to expedite prosecution.