From the abstract of Gregory C. Sisk, Measuring Law Faculty Scholarly Impact by Citations: Reliable and Valid for Collective Faculty Ranking (Jurimetrics, Forthcoming):
No single metric of faculty scholarly activity can fully capture every individual contribution. For that reason, evaluating a single professor’s scholarly work requires a nuanced, multifaceted, and individually focused assessment. However, for a contemporary sketch of the collective scholarly impact of a law school faculty, citation measurements in the legal literature are both reliable and valid.
The new Heald-Sichelman study of citations in the HeinOnline database confirms the reliability of the multiyear results of the Leiter-Sisk Scholarly Impact Ranking based on the Westlaw journals database. Despite using a different law journal database, counting citations differently, including pre-tenure faculty, and even adding download statistics into the mix, the Heald-Sichelman ranking correlates powerfully at 0.88 with the most recent Leiter-Sisk ranking. An objective citation measurement is time-sensitive and corresponds to informed awareness of law school faculty developments around the country. A citation-based ranking thus is a valid, if imperfect, proxy for faculty scholarly impact on a national scale.
With appropriate qualifications and necessary adjustments, a citation-based ranking should be considered in any evaluation of the overall quality of a law school faculty. For the U.S. News ranking of American law schools, an up-to-date, citation-based ranking would have considerable merit as an objective forward-directed control to the subjective past-looking academic reputation survey.