Interrogatories and depositions are both pretrial discovery tools, but they work very differently. Interrogatories are written questions that one party sends to another party, answered in writing and under oath, usually within 30 days. Depositions are live, in-person question-and-answer sessions where an attorney examines a witness under oath, with answers given on the spot and recorded. The written format makes interrogatories cheap and precise; the live format makes depositions better for testing credibility and following up in real time.
How Interrogatories Work
Interrogatories are a set of written questions one party sends to the opposing party. The recipient has 30 days to answer them in writing, under oath.1Legal Information Institute. Federal Rules of Civil Procedure Rule 33 – Interrogatories to Parties The answers are drafted carefully with the attorney’s help, so what comes back is typically the responding party’s most polished account of the facts.
Federal rules cap interrogatories at 25 per side, counting any sub-questions tucked inside a single numbered one. More are allowed only with the court’s permission.1Legal Information Institute. Federal Rules of Civil Procedure Rule 33 – Interrogatories to Parties That ceiling forces attorneys to pick their questions carefully, which is why interrogatories tend to focus on foundational facts: witness names, dates, medical providers, insurance details, and other background information.
The party answering is the one who signs under oath, not the attorney. The attorney only signs any objections.1Legal Information Institute. Federal Rules of Civil Procedure Rule 33 – Interrogatories to Parties That signature puts the party personally on the hook for accuracy.
One important boundary: interrogatories can only go to another party in the lawsuit. You cannot send them to a bystander, a treating doctor, or any other non-party. For information from outside the case, a different tool is needed.
How Depositions Work
A deposition is a live session where an attorney questions a person under oath, outside of a courtroom. The witness, called the deponent, answers in real time. There’s no chance to pause and polish a response with counsel before it goes on the record. Attorneys for all parties can attend and ask their own questions, and the exam follows the same general rules that apply at trial.2Legal Information Institute. Federal Rules of Civil Procedure Rule 30 – Depositions by Oral Examination
The testimony is recorded. The party noticing the deposition chooses the method, whether stenographic transcript, audio, or video, and any other party can arrange a second method at its own cost.2Legal Information Institute. Federal Rules of Civil Procedure Rule 30 – Depositions by Oral Examination Video is increasingly common because it captures tone, hesitation, and body language that a transcript flattens out.
A single deposition is limited to one day of seven hours unless the parties agree otherwise or the court extends the time.3United States Court of International Trade. Rule 30 – Depositions by Oral Examination Each side is also capped at 10 depositions total; an eleventh needs the other side’s agreement or a court order.2Legal Information Institute. Federal Rules of Civil Procedure Rule 30 – Depositions by Oral Examination
Unlike interrogatories, depositions aren’t limited to parties. An attorney can depose anyone with relevant knowledge: a treating physician, a co-worker who saw an incident, an accountant who looked at the books. If the non-party won’t appear voluntarily, a subpoena under Rule 45 can compel attendance. That subpoena power has a geographic limit: a witness can only be made to travel within 100 miles of where they live, work, or regularly do business.4Legal Information Institute. Federal Rules of Civil Procedure Rule 45 – Subpoena A non-party who ignores a properly served subpoena risks contempt.
Interrogatories vs Depositions: The Practical Differences
The format gap drives almost every other difference between the two.
Interrogatory answers are built over days or weeks with full attorney involvement. Deposition answers happen in seconds, on the record, with no chance to revise. That makes interrogatories useful for collecting clean factual data and depositions useful for testing how a person actually handles questioning.
Follow-up works differently too. When an interrogatory answer is evasive, the only remedy is filing a motion to compel. In a deposition, the attorney can press on the spot, circle back to inconsistencies, and probe weak spots. Good deposition lawyers treat vague answers as openings rather than endings.
Cost is the practical factor that often decides which tool gets used. Interrogatories are cheap; the main expense is attorney time drafting and reviewing. Depositions require coordinating multiple attorneys’ schedules, paying a court reporter, sometimes renting space and hiring a videographer. Transcripts alone run several dollars per page, and a seven-hour deposition can produce hundreds. On a tight budget, interrogatories often cover fact-gathering that would cost five or ten times as much to do by deposition.
Reach is the other divide. Interrogatories only touch parties. Depositions can reach anyone with relevant knowledge, inside the case or outside it.
How Objections Work in Each
Both tools allow objections, but the mechanics are not the same.
With interrogatories, a party who thinks a question is overly broad, seeks privileged information, or is irrelevant can object instead of answering. The objection has to be stated with specificity; a vague complaint that a question is “burdensome” won’t survive. Any objection not raised in the 30-day response window is generally waived unless the court finds good cause for the delay.1Legal Information Institute. Federal Rules of Civil Procedure Rule 33 – Interrogatories to Parties
In a deposition, the clock keeps running. An attorney can state an objection on the record, but the deponent still has to answer. The objection is preserved for the court to resolve later.2Legal Information Institute. Federal Rules of Civil Procedure Rule 30 – Depositions by Oral Examination
There are only three narrow situations where an attorney can tell the deponent not to answer at all: to protect a legal privilege such as attorney-client communications, to enforce a limitation the court has already ordered, or to pause the deposition in order to ask the court to shut down abusive questioning.2Legal Information Institute. Federal Rules of Civil Procedure Rule 30 – Depositions by Oral Examination Outside those situations, instructing a witness not to answer is improper and can draw sanctions.
When Attorneys Use Each One
Experienced litigators don’t treat the two tools as interchangeable. They sequence them.
Interrogatories usually go out early. They’re efficient for building the factual skeleton of a case: identifying every doctor the plaintiff saw, pinning down the timeline, learning which employees were involved, cataloguing relevant documents. The 25-question cap keeps them blunt, but a well-drafted set can map the full shape of a dispute before anyone sits for a deposition.
Depositions come later, once the attorney knows enough to ask dangerous questions. Their real value is less about gathering facts than about testing witnesses. How does the plaintiff describe the accident when pressed for details? Does a corporate representative hold up when confronted with contradictory documents? A deposition lets an attorney gauge whether someone will be credible to a jury, and it locks the witness into a specific account. If the story changes later, the transcript becomes cross-examination material.
The two tools also feed each other. Interrogatory answers can identify the five witnesses most worth deposing. A surprising deposition admission can prompt follow-up interrogatories that force the opposing party to reconcile the admission with its official position.
How Each One Shows Up at Trial
Both carry weight at trial, but in different ways.
If a party says one thing in an interrogatory answer and something different on the witness stand, opposing counsel can read the earlier answer to the jury to point out the inconsistency. That’s part of why interrogatory responses are drafted so carefully: they become a binding written record that follows the party through the case.
Deposition transcripts have broader uses. Any party can use deposition testimony to impeach a witness whose live testimony contradicts earlier sworn statements. When the deponent is the opposing party, or an officer or representative of an opposing company, the transcript can be used for any purpose, not just impeachment.5Legal Information Institute. Federal Rules of Civil Procedure Rule 32 – Using Depositions in Court Proceedings
Depositions also act as a backup if a witness can’t make it to trial. If the witness has died, lives more than 100 miles from the courthouse, is too ill to appear, or is otherwise unavailable, the deposition can be read or played for the jury in place of live testimony.5Legal Information Institute. Federal Rules of Civil Procedure Rule 32 – Using Depositions in Court Proceedings That’s why attorneys often depose elderly or far-away witnesses even when their testimony seems uncontested. A videotaped deposition is insurance.
The Duty to Update Answers
Neither tool is “answer once and forget it.” If a party learns that an earlier interrogatory answer or disclosure was incomplete or wrong, they have a continuing obligation to supplement or correct it in a timely manner.6Legal Information Institute. Federal Rules of Civil Procedure Rule 26 – Duty to Disclose; General Provisions Governing Discovery This duty runs all the way through trial.
If a plaintiff identifies three witnesses in interrogatory responses and later realizes a fourth person saw the incident, the answer has to be updated. Sitting on the information and springing it at trial can backfire. The court can exclude the undisclosed witness entirely.7Legal Information Institute. Federal Rules of Civil Procedure Rule 37 – Failure to Make Disclosures or to Cooperate in Discovery; Sanctions
What Happens If You Don’t Comply
Ignoring discovery obligations is one of the fastest ways to lose a case you might otherwise win.
The usual first step is a motion to compel. If a party refuses to answer interrogatories or a deponent won’t answer questions, the other side can ask the court to order compliance. When that motion succeeds, the losing side typically pays the other’s legal fees for having to file it.7Legal Information Institute. Federal Rules of Civil Procedure Rule 37 – Failure to Make Disclosures or to Cooperate in Discovery; Sanctions
If non-compliance continues after a court order, sanctions escalate. The court can treat disputed facts as established in the other side’s favor, bar the non-compliant party from presenting certain evidence or defenses, strike pleadings, enter default judgment, or hold the party in contempt. On top of any of those, the court will almost always order the non-compliant party or its attorney to pay the other side’s reasonable expenses, including attorney’s fees, caused by the failure.7Legal Information Institute. Federal Rules of Civil Procedure Rule 37 – Failure to Make Disclosures or to Cooperate in Discovery; Sanctions Responding on time and in good faith, even to invasive questions, almost always costs less than the alternative.