Over the last few years, US district courts and the Court of Appeals for the Federal Circuit have applied greater scrutiny to evidence presented in patent infringement cases. While the courts have provided some clear examples of the types of evidence and testimony they are likely to reject, patent holders and alleged infringers are without specific guidelines as to the precise evidence needed. The courts have, however, emphasized that reasonable royalties should be consistent with “accepted economic principles” (IP Innovation v. Red Hat). This guest column from Law360 describes the types of evidence upon which plaintiffs or defendants might rely that are consistent with recent rulings.