Prof. Díaz-Hernández has been a witness for the plaintiffs in tobacco-related litigation. He teaches at the Pontifical Catholic University in Ponce, Puerto Rico, since 1975. He has written and published mainly on the history of Puerto Rico. His witness report can be ordered via a website. He has written reports for tobacco litigation in Puerto Rico for the plaintiffs. Díaz-Hernández acknowledged during a deposition in Alvarez v. R.J. Reynolds that he charged $275 an hour for his tobacco related litigation work.In Valle-Ortiz v. R.J. Reynolds his testimony was successfully challenged by the defence under the Daubert standard.
 See http://www.expertwitnessprofiler.com/Luis+Diaz-Hernandez/73419. Accessed 31 Oct 2014.
 Deposition of Luis Díaz-Hernández, September 21, 2004, Alvarez v. R.J. Reynolds. Westlaw reference: 2004 WL 5487028.
 Defendant’s Motion to Strike the New Expert Report of Dr. Luis E. Diaz, August 4, 2005, Vall-Ortiz v. R.J. Reynolds. Westlaw Number: 2005 WL 6141299.