If a defendant seeks information from a nonparty witness in federal court, what is the likely method?

The most appropriate method for a defendant to seek information from a nonparty witness in federal court is through an oral deposition. A deposition allows for the direct questioning of the witness, where an attorney can ask questions and obtain answers in real-time, which can be particularly useful for assessing the witness's demeanor and the context of their answers.

Oral depositions enable attorneys to gather detailed testimony that can later be used in court or to prepare for trial. This method is distinct from written interrogatories, which involve questions submitted in writing and are typically directed towards parties in the case, not nonparty witnesses.

A notice of deposition is a procedural step that accompanies the scheduling of an oral deposition, but it does not by itself serve as a method to collect information. A request for production of documents also pertains to obtaining evidence but is aimed at acquiring documents rather than oral testimony. Thus, utilizing an oral deposition is the most effective means for obtaining firsthand testimony from a nonparty witness in the context of federal civil procedure.