Legalist and realist decision-making in patent law: Validity cases in Germany

While realist approaches towards judicial decision-making have become predomi- nant, their appropriateness is much less obvious for specialized or technical fields of law, such as patent litigation, and evidence is much scarcer than for generalist courts. Addressing this scarcity, the paper assesses judge-level variation in deci- sion outcomes based on a sample of 1,722 collegial decisions on patent validity at the German Federal Patent Court. Using a Bayesian mixed membership multilevel model, we find that after controlling for variation due to other contextual factors, there remains significant statistical variation in the propensity to nullify a patent at the level of individual judges. However, judge effects are relatively weak and uncer- tain, indicating mitigation of individual deviation through collegiality. We conclude by discussing the relevance of consistent judicial outcomes beyond the studied con- text and especially in transnational harmonization processes, such as initialized by the recent establishment of the Unified Patent Court.