Which of the following best illustrates a valid use of interrogatories?

Interrogatories are a formal set of written questions that one party in a lawsuit sends to another party as part of the discovery process. Their primary purpose is to obtain information that is relevant to the case, often specific factual admissions that can clarify positions and establish facts for trial.

In this context, selecting the option that involves obtaining specific factual admissions from the opposing party captures the essence of what interrogatories are designed to achieve. They enable one party to probe the opposing party's knowledge and stance about the facts in a case, which can help shape the legal strategy and understanding of the issues at hand.

The other options do not accurately reflect the primary function of interrogatories. For instance, compiling a list of witnesses falls more under the purview of depositions or requests for production, rather than being a direct aim of interrogatories. Summarizing evidence collected is not something that interrogatories are intended for, as these questions focus on the facts already known rather than summarizing information. Lastly, seeking legal advice from an expert is not something interrogatories can accomplish; they are meant for gathering factual information from the parties involved, not for obtaining professional legal opinions.

Thus, the correct answer highlights the fundamental role of interrogatories in the litigation process.