In contrast to retained testifying experts, non-retained testifying experts are experts who had personal involvement in the events underlying the litigation, such as consultants or contractors; they are fact witnesses who are also providing expert opinions. Unlike retained experts who are subject to extensive disclosure requirements, non-retained experts need only provide a disclosure of the subject on which they intend to testify and a summary of the facts and opinions they intend to provide. Compare Fed. R. Civ. P. 26(a)(2)(B) with Fed. R. Civ. P. 26(a)(2)(C). In 2010, Federal Rule of Civil Procedure 26(b) was amended to provide express protections for retained experts' draft reports and, with certain exceptions, communications with counsel, but the same protections were not expressly extended to non-retained experts. See Fed. R. Civ. P. 26(b) advisory committee's note to 2010 amendment. The Advisory Committee's notes, however, state that Rule 26(b) "does not exclude protection" for non-retained experts. Therefore, since the 2010 amendment, courts have determined whether counsels' communications with non-retained experts are discoverable on a case-by-case basis.