What Substantive Law Governs Sufficiency of a Privilege Log in a Federal Court Sitting in Diversity?

McSwain v. HOMAG Machinery N. America, Inc., 2026 WL 2427645 (D. S. Car. Aug. 19, 2026), is a product liability and wrongful death action in which federal jurisdiction was based on diversity of citizenship.  The decedent had been repairing a machine.  Another worker turned off the power, causing the motor to drop on him.

One defendant’s privilege log was untimely.  Plaintiff moved to compel, challenging privilege based on alleged subject matter waiver by production of privileged materials and also on an alleged untimely and deficient privilege log.

The court wrote that: “In diversity cases, the application of the attorney-client privilege is governed by state law—in this case, the law of South Carolina.”

As to the waiver issue, the court found that the communications between defendant’s general counsel and others were not for the primary purpose of securing legal advice.  Because they were not privileged, there was no subject matter waiver by disclosure.

Turning the choice of law issue regarding the privilege log, the court wrote:

As an initial matter, Stiles mistakes the extent to which South Carolina law governs the conflict over its privilege log. In Erie R.R. v. Tompkins, 304 U.S. 64, 58 (1938), the Supreme Court held that federal courts sitting in diversity must apply state substantive law. Under the Erie Doctrine, “a federal court is to apply state substantive law and federal procedural law in diversity cases.” …. Assertion of attorney-client privilege requires a party to satisfy both procedural and substantive criteria…. In claiming that the privilege applies, Stiles is correct that the Court’s assessment of whether attorney-client privilege applies to the documents at issue is governed by South Carolina law…. However, the production of a privilege log asserting attorney-client privilege over certain documents in order to withhold that information from discovery is procedural and, therefore, governed by federal law…. Accordingly, the Court applies federal law to determine whether Stiles’ privilege log was sufficient. [cleaned up; emphasis added].

The court held: “Upon review, the Court finds that these disclosures on Stiles’ privilege log are insufficient to allow Plaintiff to determine whether Stiles has properly asserted privilege over these documents.”

The court determined that it had four options: “(1) give the party another chance to submit a more detailed log; (2) deem the inadequate log a waiver of the privilege; (3) inspect in camera all of the withheld documents; and (4) inspect in camera a sample of the withheld documents.”  It engaged in detailed factual analysis and granted plaintiff’s motion in part and denied it in part.

This blog was initially posted on  Electronic Discovery Reference Model.