Ariel Roman’s motion to quash the subpoena duces tecum that Chicago Police Officer Melvina Bogard’s lawyer sent to his retained expert on police practices under Federal Rule of Civil Procedure 45 presented a dispute on which there is “substantial disagreement across the country.”The question for Magistrate Judge Sunil R. Harjani was “whether a subpoena under Rule 45 is a permissible means of obtaining information from an opposing party’s testifying expert witness or whether Rule 26(a)(2) constitutes the only available …