An expert deposition serves three purposes: locking the opinions, building the exclusion motion, and preparing cross-examination.

Lock the opinions. Establish that the report contains every opinion the expert will offer, that no further work is planned, and that the expert will not supplement absent new information. This forecloses opinions appearing for the first time at trial.

Establish the assumptions. Every opinion rests on assumptions supplied by counsel or drawn from the record. Identify each, and establish what happens to the opinion if an assumption fails. This is where cases are won: an opinion that collapses on a fact the jury may not accept.

Methodology. What method was used, whether it is generally accepted, whether it was applied as the literature prescribes, what alternatives were considered and rejected, and whether the expert has applied the method the same way in other matters.

Materials. Everything considered, everything discarded, and communications that are discoverable in the applicable system.

Prior work. Prior reports, testimony, publications and any prior exclusion.

Do not argue. The deposition is for gathering. Confrontation warns the expert and improves their trial testimony.