Common Attacks on Economic Damage Experts and How to Prepare for Them
Executive Summary
In high-stakes disputes, economic damage opinions are frequently attacked on reliability, relevance, and “fit” to the case facts. The most effective preparation is not rhetorical—it is structural: a clearly defined damages theory, a method that matches that theory, complete and traceable data, transparent assumptions, and exhibits that let a judge or jury follow the math without guessing.
This article summarizes when challenges most commonly arise, the accepted frameworks experts rely on, the documents that typically make or break defensibility, and the attack points opposing experts and counsel use—along with practical rebuttal strategies that keep the analysis grounded and understandable.
When This Issue Arises
Challenges to economic damage opinions typically surface at predictable points in the litigation lifecycle:
Early case strategy and discovery planning (to define the damages theory and identify missing records).
Expert discovery and depositions (to probe assumptions, data sufficiency, and method selection).
Motions to exclude or limit expert testimony (often framed under reliability and relevance standards).
Mediation or settlement discussions (where the strength of the model influences negotiation leverage).
Pre-trial exhibit preparation and trial testimony (where clarity, consistency, and “teachability” matter most).
In practice, the risk of a serious attack increases when the damages model depends on projections, counterfactual “but-for” scenarios, disputed causation, or incomplete records; or when the claimed loss is large relative to the business’s historical performance.
Accepted Methods and Preparation Frameworks
Courts and fact-finders generally expect economic damages work to follow a disciplined workflow: (1) define the damages theory, (2) select methods that match the theory and available evidence, (3) build calculations from traceable data, (4) disclose assumptions, and (5) stress-test the result against reasonable alternatives.
Method selection should track the damages theory
Common pairings include:
**Business interruption / temporary disruption** → before-and-after or comparable-period analysis, supported by saved-cost treatment and documented mitigation.
**Breach of contract / lost sales** → yardstick/benchmark methods, customer-level analysis, or market-based comparables that isolate causation.
**Lost profits vs. diminution in value** → finite-period cash flow loss generally points to lost profits; permanent/indefinite impairment often points to a value-based framework.
**Employment disputes (back pay/front pay)** → earnings and benefits modeling with mitigation offsets and present-value discounting when required.
Numeric example: business interruption lost profits
Assume a restaurant is forced to close for one day and claims lost profits for that day based on prior comparable Fridays:
Projected lost sales: $2,925
Saved costs (non-continuing expenses):
• Cost of goods sold (35%): $1,024
• Credit card fees (2%): $59
• Supplies (5%): $146
• Payroll (20%): $585
Total saved costs: $1,814
Lost profits: $2,925 − $1,814 = **$1,111**
This example is defensible only if the inputs are supported (historical sales detail, consistent margins, and a documented basis for which expenses are truly saved).
Present value and discounting
When damages include future amounts (for example, future lost earnings or future cash flows), many fact patterns require the analysis to address time value of money. Even when the ultimate trier of fact decides the exact discount approach, the expert is often attacked on whether the chosen rate is supported and applied consistently. A practical preparation step is a short sensitivity table that shows outcomes across a reasonable range rather than a single “magic” rate.
Documents and Data Checklist
Well-supported damage opinions usually share one trait: the workpapers trace each key input to documents that can be authenticated. A typical core document set includes:
**Pleadings and a liability timeline** (to define theory, triggering event, and damages period).
**General ledger detail and bank/processor records** (often more probative than high-level statements).
**Monthly P&L, balance sheets, and cash flow data** for multiple pre-event periods.
**Tax filings and payroll registers** (to corroborate revenue, wages, owner compensation, and benefits).
**Sales detail** by product, location, customer, and channel (for causation and segmentation).
**Contracts, pricing, invoices, and purchase orders** (to anchor volume and price assumptions).
**Budgets/forecasts created before the event** plus board/management communications supporting them.
**Industry benchmarks and macro indicators** relevant to the business (used as reasonableness checks).
**Mitigation documentation** (replacement vendors, alternate jobs, substitute products, cost controls).
**Opposing expert materials** (report, exhibits, deposition transcript, prior testimony where available).
Pitfalls and Common Attacks, With Rebuttal Strategies
Opposing experts and counsel usually focus on a small set of repeatable attack themes. Preparing for these themes early prevents last-minute rework and reduces testimony risk.
Attack 1: “The method is not reliable or not generally accepted.”
What goes wrong: the model appears ad hoc, outcome-driven, or inconsistent with the field’s accepted approaches.
Rebuttal strategy: clearly articulate why the selected method fits the damages theory and available records; show that the approach is repeatable; and keep a short list of alternative methods that were considered (and why they were less appropriate).
Attack 2: “The opinion doesn’t fit the facts of the case.”
What goes wrong: inputs and assumptions are disconnected from what actually happened (wrong damages period, wrong product mix, wrong customer base, or missing key causal events).
Rebuttal strategy: build the model around a documented timeline and segment data where possible (by customer, location, product line). Demonstrate that key assumptions tie to exhibits and testimony.
Attack 3: “The expert assumed liability or causation.”
What goes wrong: the report reads as if the expert decided legal issues, or it ignores alternative causes.
Rebuttal strategy: define the model’s conditional nature (“assuming the fact-finder determines X, the resulting damages are Y”), and include explicit consideration of alternative drivers (market changes, seasonality, operational issues) using comparative data.
Attack 4: “The data is insufficient or selectively chosen.”
What goes wrong: cherry-picked periods, missing records, or unexplained exclusions create credibility problems.
Rebuttal strategy: document the data received, identify limitations, and explain how gaps were handled (for example, triangulation using bank deposits, POS summaries, vendor invoices, or industry ranges). Show completeness tests and cross-checks.
Attack 5: “Assumptions are speculative.”
What goes wrong: growth rates, margins, mitigation, or discount rates are not supported by evidence.
Rebuttal strategy: disclose assumptions in a dedicated table, cite their factual basis (internal history, pre-event forecasts, third-party benchmarks), and provide sensitivity ranges showing the conclusion remains reasonable under alternative inputs.
Attack 6: “The expert is outside their lane.”
What goes wrong: the expert offers opinions outside their demonstrated competence (for example, technical engineering causation, medical diagnosis, or legal conclusions).
Rebuttal strategy: keep testimony focused on economic and financial issues within the expert’s training and experience, and use other qualified experts for technical causation where needed.
Attack 7: “The expert is biased.”
What goes wrong: inconsistent positions across cases, inflammatory language, or lack of transparency creates the appearance of advocacy.
Rebuttal strategy: maintain neutral language, consistent methods, and clean workpapers. Where there are judgment calls, explain them and show the alternative analyses considered.
FAQs
Should counsel use a consulting expert, a testifying expert, or both?
Often both. A consulting expert can help shape discovery and stress-test theories early, while a testifying expert presents the final opinion. The best structure depends on timing, budget, and whether early work product needs to remain non-testimonial.
What is the fastest way to spot weaknesses in an opposing damages report?
Look for unsupported assumptions, a damages period that does not match the timeline, missing mitigation, inconsistent treatment of saved costs, and inputs that cannot be traced to source documents.
How can an expert make complex damages models understandable to a jury?
Use a short timeline, a one-page assumptions table, and a step-by-step calculation exhibit. Then add a sensitivity table that shows how results change under reasonable alternatives.
What are common red flags that trigger motions to limit or exclude damages opinions?
Ad hoc methods, unexplained data exclusions, speculative projections, failure to address alternative causes, and conclusions that appear to decide legal issues rather than quantify economics.
How should missing or incomplete records be handled without overreaching?
Disclose the limitation, use corroborating records (bank deposits, processor reports, vendor invoices), and present bounded estimates or ranges rather than pretending the gap does not exist.
What preparation steps reduce deposition and cross-examination risk the most?
Align the model to a documented timeline, trace every key input to an exhibit, disclose assumptions in one place, and rehearse clear answers to the expected attacks on method, data sufficiency, causation, mitigation, and discounting.
Sources
Federal Rules of Evidence, Rule 702 (expert testimony framework)
Daubert v. Merrell Dow Pharmaceuticals, Inc. (reliability gatekeeping principles)
Kumho Tire Co. v. Carmichael (reliability principles applied to technical/specialized expertise)
Federal Judicial Center — Reference Manual on Scientific Evidence (general guidance for evaluating expert evidence)
AICPA — Statement on Standards for Forensic Services (SSFS No. 1)
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Disclaimer: This article is for informational purposes only and does not constitute legal advice. Outcomes depend on specific facts and circumstances.
