What describes the basis of an expert's opinion?

• A. The judge's perception of the evidence.
• B. The expert's own ideas and hypotheses, without data.
• C. The facts or data in the particular case upon which an expert relies.
• D. The opinions of other witnesses regardless of data.

Answer: (C)

The basis of an expert’s opinion is the facts or data in the particular case that the expert relies on to form the opinion. This means the opinion rests on information the expert has reviewed or observed—documents, records, measurements, test results, or other case-specific data—applied through the expert’s specialized methods. The opinion isn’t simply the expert’s own ideas or hypotheses without data, nor is it based on the judge’s impression of the evidence or on other witnesses’ opinions in the abstract. The data and facts the expert relies on are what make the opinion defensible as grounded in the case.