California companies who want to extend the terms of their patents may find that court precedents prevent them from using child patents to do so. In one December 2015 judgment, the U.S. District Court for the Western District of Michigan decided that an automotive holdings company was justified in seeking a judgment of invalidity against an electronics company that had filed a child patent in 1999.
The child patent was filed with a priority claim that dated back to 1993, but it wasn't issued until 2008 because another patent that was a grandchild of its parent was subject to a terminal disclaimer. This situation gave the patent an expiry date of 2013, which was 20 years after the priority date of the original parent.
In its decision, the court decided that the grandchild patent bound by the terminal disclaimer qualified as an obviousness-type double patent against the original. It also cited another case that stated double-patenting references could be established for patents that referenced earlier patents and expired before them. Observers, however, pointed out that such claims may be difficult to differentiate because of the unique parent-child relationships that apply to specific cases.
Those who want to use patents for business purposes can't take them for granted. These protections don't stop others from engaging in litigation or trying to misuse intellectual property, so they may require defense or enforcement. Some companies have to pursue patent term adjustments and unique arrangements and maintain existing protections following patent expiration. A patent law attorney can provide clients with further guidance on these and other matters.