How Maritime Expert Witnesses Get Excluded Under Daubert — and How to Survive the Cross

Daubert is not a medicine problem. Under Kumho Tire and the 2023 amendment to Federal Rule of Evidence 702, the trial court's gatekeeping applies to every form of specialized testimony — maritime included. A 20-year study of 2,842 challenges to non-medical experts found that roughly half of those opinions were excluded or partially excluded, and the single most-cited reason was “unreliable methodology.”

The exclusion rarely happens in a written motion alone. It is built, piece by piece, in the deposition cross-examination — where opposing counsel walks a maritime expert into conceding scope, methodology, or an assumption that unravels the whole opinion. Here are the three traps, and how a prepared expert answers each one.

The three ways maritime experts lose ground

Scope: testifying outside your lane

The cross-examiner's question sounds simple:

You opine the vessel was operated negligently — but you never held a master's license on this class of vessel, correct?

Why it works: The license/scope attack. Anchor to the navigation rules and seamanship standards.

A stronger answer: “I apply the COLREGS and accepted seamanship standards, which govern the operation, and the documented voyage data; I disclosed my basis and the standards I relied on.”

Methodology: the reliability attack

The cross-examiner's question sounds simple:

Your reconstruction relied on the deck logs — but they're not a second-by-second record, are they?

Why it works: Methodology / data resolution. State what the logs and AIS can and can't establish.

A stronger answer: “Correct. I used the logs, AIS, and other available data and stated the temporal resolution and its effect on the reconstruction.”

Assumptions: the one premise that sinks the opinion

The cross-examiner's question sounds simple:

You assume the sea state was as reported in the log — but conditions vary, don't they?

Why it works: The sea-conditions assumption. Corroborate and flag.

A stronger answer: “I corroborated the reported conditions against weather and AIS data where available and flagged anything unconfirmed.”

How to prepare for the cross before you're sworn in

Every one of those traps is defeatable — but not by reading your report one more time. The experts who survive the cross have done three things:

• Rehearsed the cross-examination out loud, repeatedly, against a realistic examiner — so the scope concession, the methodology defense, and the assumption hedge are second nature.
• Mastered the record, so that when counsel asks them to recall the one line buried in thousands of pages of the logs, charts, and vessel records, they can produce it in seconds rather than fumble.
• Stress-tested the report against FRE 702 — finding the reliability gaps before opposing counsel does.

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