The Federal Circuit warned against relying on conclusory expert testimony in TQ Delta, LLC v. Cisco Sys., Inc., Nos. 2018-1766, 2018-1767 (Fed. Cir. Nov. 22, 2019).

In response to TQ Delta’s patent infringement suit, Cisco filed two IPR petitions, challenging TQ Delta’s patents on obviousness grounds. The Board instituted both proceedings and found all the challenged claims obvious over the combination of two prior art patents. TQ Delta appealed.

In reversing the Board, the Federal Circuit first noted that the two prior art patents the Board relied on solved different problems than that solved by TQ Delta’s patents. In making its decision that it would be obvious to combine those patents, the Board relied exclusively on the testimony of Cisco’s expert. The Federal Circuit characterized the expert’s testimony as “brief, high-level explanation” untethered to any contemporaneous or supporting evidence. The Federal Circuit thus reversed the Board’s obviousness determinations under the substantial evidence standard, emphasizing that rejections on obviousness grounds could not rest on mere conclusory statements.

The Federal Circuit also observed that conclusory expert testimony is inadequate as substantial evidence in other areas of patent law, including enablement, written description, anticipation, and infringement.