A motion to exclude expert testimony is often the most consequential pretrial motion in a commercial case, because excluding a damages expert can end the claim.

Timing. By the deadline in the scheduling order, usually with dispositive motions. Later challenges risk waiver, and objections at trial are disfavoured where the basis was known.

Grounds. Qualification; sufficiency of the facts or data; reliability of the principles and methods; reliable application to the facts; and fit between the opinion and the issue.

The record. The report, the deposition, the materials relied on, and the literature. A challenge without a deposition rarely succeeds, because the weaknesses are established by the expert’s own answers.

Hearing. Courts may decide on the papers or hold a hearing with live testimony. Requesting a hearing is worthwhile where the expert performs poorly under questioning.

Partial exclusion. More common than complete exclusion — particular opinions struck while the expert testifies on others. Frame the motion to identify each opinion challenged rather than attacking the expert generally.

Weight versus admissibility. The most common ruling is that the objections go to weight. Anticipate it and identify which defects are true methodological failures rather than disagreements about inputs.