How Agriculture 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 — agriculture 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 agriculture 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 agriculture experts lose ground

Scope: testifying outside your lane

The cross-examiner's question sounds simple:

You opine the herbicide drift caused the crop loss — but you didn't sample the field at the time, did you?

Why it works: Tie causation to records and tissue data; address alternative stressors.

A stronger answer: “I analyzed the documented application records, the symptomology, and the available tissue/soil data and addressed alternative causes; I noted where contemporaneous sampling was unavailable.”

Methodology: the reliability attack

The cross-examiner's question sounds simple:

Your yield-loss number relied on comparison fields — those differ in soil and management, don't they?

Why it works: Methodology / comparison basis.

A stronger answer: “I selected comparable reference fields, adjusted for known differences, and disclosed the basis and limits.”

Assumptions: the one premise that sinks the opinion

The cross-examiner's question sounds simple:

You assume normal weather — but conditions that season varied, didn't they?

Why it works: The weather/condition assumption. Use actuals.

A stronger answer: “I incorporated the actual weather and field conditions and addressed their effect rather than assuming normal conditions.”

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 field records, application logs, and yield data, 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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