| name | expert-impeachment |
| title | Expert Witness Impeachment |
| description | Surfaces inconsistencies, opinion shifts, methodological flaws, and credential discrepancies across expert reports, transcripts, CVs, and publications for impeachment, cross-examination, and exclusion motions. Trigger when the user references expert impeachment, expert report analysis, Daubert or Frye challenges, deposition prep against an expert, or credibility attacks on opposing expert witnesses. |
| author | CaseMark |
| author_url | https://github.com/CaseMark/skills/tree/main/skills/legal/expert-impeachment |
| license | Apache-2.0 |
| version | 0.1.0 |
| execution_mode | open |
| jurisdiction | us |
| practice | litigation |
| language | en |
| tags | ["analysis"] |
Expert Witness Impeachment
Builds a citation-ready inconsistency map to challenge expert credibility, reliability, and admissibility.
Quick Start
- Collect all expert materials: reports, supplements, rebuttals, deposition/trial transcripts, declarations, CV, publications, prior testimony, data/appendices.
- Confirm page/line or Bates-citable versions of each source.
- Identify the case theory, key disputed issues, and governing admissibility standard (Daubert, Frye, or local rule).
- Proceed through the workflow steps below in order.
Workflow
1. Source Inventory
Build a table of every source document with columns: Source, Date, Type, Citation Format, Notes.
2. Opinion Chronology
Map the expert's opinions over time with columns: Date, Document/Testimony, Key Opinion Statement, Cite. Track how positions evolved across filings.
3. Inconsistency Log
For each inconsistency found, log:
- ID — unique identifier
- Category — one of:
Opinion Change, Methodology, Facts/Assumptions, Credentials, Scope Creep, Prior Testimony Conflict, Publication Conflict, Math/Calculation Error
- Statement A and Statement B — exact quotes with pinpoint cites
- Delta — nature of the conflict
- Materiality — H/M/L
- Admissibility Impact — Reliability, Fit, Qualifications, or combination
- Explanation Offered — any justification on record
- Cross-Exam Hook — suggested line of questioning
4. Methodology Audit
- Identify each dataset, test, model, or protocol relied upon.
- Confirm consistent application across reports and testimony.
- Flag changes in assumptions, variables, or inputs without explanation.
- Flag conclusions not supported by stated method.
- Note departures from the expert's own published standards or prior testimony.
- Record concessions on limitations, error rates, or missing data.
5. Credentials & Bias Check
Verify each claimed credential. Log: Claim, Source, Verification Status, Conflict, Materiality. Flag financial bias, repeat retention patterns, and advocacy history.
6. Materiality & Strategy Ranking
