What Are the Methods of Discovery in Civil Cases?

The methods of discovery in civil cases in federal court come down to six tools: interrogatories, requests for production, depositions, requests for admission, physical and mental examinations, and subpoenas. Each one does something the others can’t, and knowing which to use—and when—is the difference between a discovery plan that builds your case and one that burns through your budget. None of them become available until the parties hold a planning conference and exchange mandatory initial disclosures covering witnesses, documents, damages calculations, and insurance coverage.¹ After that, the formal tools open up.

Interrogatories

Interrogatories are written questions one party sends to another. The recipient must answer them under oath, in writing, within 30 days of service.² The person answering signs the responses; the attorney signs any objections.

Federal rules cap each side at 25 interrogatories, counting every subpart, unless the court allows more or the parties agree otherwise.² That ceiling forces discipline. Interrogatories work best for nailing down basic facts early: who was present, what documents exist, what legal theories the other side intends to rely on.

One variety worth knowing is the contention interrogatory, which asks a party to state the factual basis for a specific claim or defense. These are permitted even though they essentially ask for legal positions, and courts sometimes defer the deadline for answering them until other discovery has progressed.² They force the opposing side to commit to a position in writing, which can be useful later if their story shifts.

Requests for Production of Documents

A request for production is a formal demand for documents, electronically stored information, or physical items. In a contract dispute, that could mean emails between the parties, financial records, and the signed agreement. In an employment case, personnel files, internal investigation materials, and timekeeping records.

The responding party has 30 days to agree to produce the items or state specific objections.³ When you produce documents, you have two options: hand them over the way they’re kept in the normal course of business, or label them to match the categories in the request. A document dump of thousands of unsorted pages violates the rule.

Electronic data brings its own wrinkles. If the request doesn’t specify a format, you must produce files in the form you ordinarily keep them or in a reasonably usable format.³ You don’t have to produce the same material in multiple formats, but handing over a database export that requires proprietary software to open doesn’t meet the standard. Metadata like file creation dates and author information is often discoverable too, so stripping it before production can create problems.

Depositions

A deposition is sworn, out-of-court testimony given in response to live questioning. It’s the only discovery method that lets you watch a witness answer in real time, which makes it invaluable for assessing credibility, locking in testimony, and chasing unexpected leads. Attorneys for all parties attend, and a court reporter or videographer records the testimony.

Each side is limited to 10 depositions, and each one is capped at a single day of seven hours.⁴ The court can grant more depositions or extend the time, and the parties can stipulate to different limits without court approval. Scheduling requires reasonable written notice stating the time and place.

The questioning attorney can cover anything within the broad scope of discovery. Opposing counsel may object for the record, but the witness still answers unless the objection involves privilege, a court-imposed limitation, or a motion to terminate the deposition. That’s the key difference from trial: most objections are preserved but don’t stop the testimony.

Depositions are also the most expensive discovery tool. Court reporter fees, transcripts, and video recording add up quickly, and the party noticing the deposition usually bears those costs upfront.

Corporate Representative Depositions

When you need testimony from a company rather than a specific individual, you serve a deposition notice describing the topics you want covered. The organization then designates one or more representatives to testify on its behalf.⁴ The designee doesn’t need personal knowledge; the organization has to prepare that person to speak for the entity. Since 2020, the rules also require both sides to meet and confer about the deposition topics beforehand.

Expert Witness Depositions

Deposing the other side’s expert follows the same general process, with one meaningful difference: the party requesting the deposition pays the expert’s reasonable fees for preparation and testimony time.¹ Expert rates can be steep, so factor that into your budget before noticing the deposition.

Requests for Admission

Requests for admission ask the other side to confirm or deny specific facts, how the law applies to the facts, or the authenticity of particular documents. They don’t uncover new information. They narrow the field. If the other side admits that a contract was signed on a given date or that a document is genuine, neither party has to spend trial time proving a point no one actually disputes.

The responding party has 30 days to serve a written answer or objection.⁵ This is where the tool bites: miss the deadline, and the matters are automatically deemed admitted. Courts don’t treat that lightly. An unintended admission can lock you into facts that gut your case, and getting a court to withdraw a deemed admission requires showing both that withdrawal wouldn’t prejudice the other side and that the admission doesn’t accurately reflect the truth. Calendar this deadline carefully.

An admission applies only to the pending lawsuit. It cannot be used against you in a different case.

Physical and Mental Examinations

When a party’s physical or mental condition is directly at issue, the court can order that person to submit to an examination by a licensed professional.⁶ This comes up most often in personal injury cases, where the defendant wants an independent medical evaluation of the plaintiff’s claimed injuries.

Unlike the other discovery methods, this one requires a court order. The party seeking the examination must show good cause and that the condition is genuinely in controversy. You can’t order a mental exam just because you think the other side is being difficult; the person’s mental state has to be a real issue, such as a claim for emotional distress damages. The examined party is entitled to a copy of the examiner’s report, and requesting that report may trigger an obligation to share their own medical reports on the same condition.

Subpoenas

The first five methods apply to parties in the lawsuit. When you need documents or testimony from someone who isn’t a party, you use a subpoena. A subpoena can compel a non-party to produce documents, appear for a deposition, or both.⁷ It must be formally served, and it carries the force of a court order.

The recipient has defenses. A non-party can move to quash or modify the subpoena, and the court must grant that motion if the subpoena fails to allow reasonable time to comply, demands travel beyond the geographic limits in the rules, seeks privileged material, or imposes an undue burden.⁷ The court also has discretion to quash a subpoena that would force disclosure of trade secrets or an unretained expert’s opinions.

The party issuing the subpoena must take reasonable steps to avoid imposing undue expense on the non-party. If a compliance dispute arises, the motion is heard in the court where compliance is required, which may be different from the court handling the underlying case.

Scope and Limits That Apply to Every Method

Across all six tools, you can seek any information relevant to a claim or defense, and the material doesn’t have to be admissible at trial to be discoverable.¹ You can chase leads that wouldn’t themselves qualify as evidence, as long as they’re reasonably connected to the case.

The main constraint is proportionality. Courts weigh six factors when deciding whether a request goes too far: the importance of the issues, the amount in controversy, each side’s relative access to the information, the parties’ resources, how useful the discovery would be in resolving the dispute, and whether the burden outweighs the likely benefit.¹ A defendant in a small-dollar contract case can push back on a demand to review ten years of company-wide email, while the same request might be perfectly reasonable in a multimillion-dollar fraud case.

Privilege and Work Product

Two categories of information are shielded even when relevant. Attorney-client privilege protects confidential communications between you and your lawyer. Work-product protection covers materials your legal team prepared in anticipation of litigation, such as research memos, strategy notes, and draft filings.⁸ If you withhold documents on either ground, you must provide a privilege log describing what was withheld in enough detail for the other side to evaluate the claim without revealing the protected content.¹

Protective Orders

When discovery threatens to expose trade secrets, cause embarrassment, or impose an unreasonable burden, either side can ask the court for a protective order on a showing of good cause. The court has wide latitude: it can limit the scope of a request, restrict who sees certain documents, require that depositions be sealed, or block a particular line of questioning entirely.¹ Before filing the motion, you must certify that you tried to resolve the dispute with the other side first.

Preserving Evidence and Enforcing Discovery

Once litigation is filed or reasonably anticipated, every party must preserve evidence that may be relevant. This covers physical documents, electronic files, voicemails, text messages, and anything else that could matter. Parties typically issue internal litigation hold notices directing employees to stop deleting or overwriting potentially relevant records.

Losing evidence that should have been preserved—spoliation—can trigger measures to cure the prejudice. When the destruction was intentional, courts can go further, including instructing the jury to presume the lost evidence was unfavorable, entering a default judgment, or dismissing the case.⁹

If the other side stonewalls, gives evasive answers, or ignores a request, you can file a motion to compel. Before filing, you must certify that you tried in good faith to resolve the dispute without the court’s involvement.⁹ Judges take that meet-and-confer requirement seriously, and motions filed without a genuine attempt at resolution often get denied.

If the motion is granted, the court must order the non-complying party or their attorney to pay the reasonable expenses the moving side incurred, including attorney’s fees, unless the noncompliance was substantially justified. For more serious violations, including ignoring a court order compelling discovery, courts can treat disputed facts as established against the disobedient party, bar them from introducing certain evidence, strike their pleadings, enter a default judgment, dismiss the case, or hold the party in contempt.⁹ Discovery abuse is one of the fastest ways to lose a case you might otherwise have won.

1
Cornell Law School. Federal Rules of Civil Procedure Rule 26 – Duty to Disclose; General Provisions Governing Discovery
2
Cornell Law School. Federal Rules of Civil Procedure Rule 33 – Interrogatories to Parties
3
Cornell Law School. Federal Rules of Civil Procedure Rule 34 – Producing Documents, Electronically Stored Information, and Tangible Things
4
Cornell Law School. Federal Rules of Civil Procedure Rule 30 – Depositions by Oral Examination
5
Cornell Law School. Federal Rules of Civil Procedure Rule 36 – Requests for Admission
6
Cornell Law School. Federal Rules of Civil Procedure Rule 35 – Physical and Mental Examinations
7
Cornell Law School. Federal Rules of Civil Procedure Rule 45 – Subpoena
8
Cornell Law School. Federal Rules of Evidence Rule 502 – Attorney-Client Privilege and Work Product; Limitations on Waiver
9
Cornell Law School. Federal Rules of Civil Procedure Rule 37 – Failure to Make Disclosures or to Cooperate in Discovery; Sanctions