Discovery (law)

Discovery is a pretrial stage in lawsuits under common law systems, where parties use civil procedure rules to gather evidence from one another. Common methods include interrogatories, requests for documents or admissions, and depositions. Evidence can also be obtained from nonparties through subpoenas. If a discovery request faces objections, the requesting party can ask the court to intervene by filing a motion to compel. Conversely, anyone resisting discovery—whether a party or nonparty—can seek a protective order from the court.

The roots of discovery trace back to early English equity practice in the Court of Chancery. Plaintiffs in equity had to include "positions" in their bills—statements of evidence they assumed existed and believed the defendant knew. These resembled modern requests for admissions, requiring the defendant to simply admit or deny them. This practice originated in canon law, which borrowed from Italian communal courts of the early 1200s; Roman law had no equivalent.

Between the reign of Elizabeth I and the late 1600s, positions gave way to interrogatories—written questions the defendant had to answer under oath, based on personal knowledge and documents. However, these interrogatories were limited: they could only seek admissible evidence (not merely evidence leading to admissible evidence), and only evidence supporting the plaintiff’s case, not the defendant’s. Worse, the process was one-sided—interrogatories could only be part of a plaintiff’s initial bill. A defendant wanting evidence for their defense had to file a separate cross-bill.

Common law courts had no discovery, but equity’s availability drew litigants from those courts. They began filing equity bills to obtain discovery for their common law cases. By the mid-1400s, a new device emerged: the bill to perpetuate testimony. This was used when a potential witness was elderly or ill and might not survive to testify at trial.

In such proceedings, written interrogatories were read aloud to the witness in a closed session, without parties or lawyers present. The witness’s attendance was secured by a subpoena ad testificandum, served at least 14 days beforehand. In London, examinations occurred before a master or examiner at Chancery Lane. Elsewhere, attorneys jointly agreed on lay commissioners—typically four, with two needed for a quorum—who could not be interested parties. The court then authorized them via a dedimus potestatem.

The examiner appointed a clerk to record the witness’s oral answers under oath. These were written as a continuous third-person narrative, not as verbatim questions and answers. For example, surviving narratives from a 1643 enclosure riot in Whittlesey show striking similarities, suggesting witnesses gave yes-or-no answers to the same interrogatories. In London, the witness signed or marked the end of the narrative; outside London, the clerk copied it onto parchment. The sealed document was not revealed—or “published”—to parties or counsel until shortly before trial. An 1899 treatise explained that this method gave the witness “ample time” for “calm recollection” and a chance to correct the record, unlike the “severe and rapid cross-examination” at common law trials, which could cause errors from memory lapses.

This ex parte pretrial examination, conducted under equity court authority, became known as a “deposition.” It continued as a way to preserve evidence for common law cases and also became the standard method for developing facts in equity courts.