In Centrak, Inc. v. Sonitor Technologies, Inc., [2017-2510] (February 14, 2019), the Federal Circuit reversed the district court’s determination that the claims of U.S. Patent No. 8,604,909 are invalid for lack of written description, and non-infringement. The ’909 patent relates to systems for real-time location (RTL), which allow users to locate and identify portable devices in a facility.

The test for sufficiency of a patent’s written description is whether the disclosure of the application relied upon reasonably conveys to those skilled in the art that the inventor had possession of the claimed subject matter as of the filing date. The district court determined that the ’909 patent lacked adequate written description support for an RTL system that relied on ultrasound-based communication from the base stations to the portable devices. However, the Federal Circuit found genuine issues of material fact remain as to whether disclosure of the implementation details that the district court identified is necessary to satisfy the written description requirement.

The Federal Circuit rejected the district court’s reliance on the fact that the specification devoted relatively less attention to the ultrasonic embodiment compared to the infrared embodiment, noting that in ScriptPro it explained that “a specification’s focus on one particular embodiment or purpose cannot limit the described invention where that specification expressly contemplates other embodiments or purposes.” The Federal Circuit instructed that the written description requirement does not demand either examples or an actual reduction to practice; a constructive reduction to practice may be sufficient if it identifies the claimed invention and does so in a definite way.