Expert Deposition Framework

Why depose the sampling expert.

In multi-plaintiff PAGA cases, plaintiff's counsel often retains a statistical expert to extrapolate violation rates from a sample to the full aggrieved employee population. The expert's methodology determines the exposure number. If the sample is flawed, the extrapolation is unreliable — and the exposure model collapses. The expert deposition is the defense's primary opportunity to expose methodological weaknesses before trial.

The Duran framework.

Duran v. U.S. Bank National Assn. (2014) 59 Cal.4th 1 established that statistical sampling in employment litigation must satisfy due process requirements: the sample must be representative, the methodology must be sound, and the defendant must have the opportunity to present individualized defenses. The expert deposition tests each of these requirements.

01

Domain 1 — Population Definition

Multi-Location Employer

The employer operates 8 locations across 3 counties. The expert includes all employees at all locations in the population — but 3 locations use a different timekeeping system with automatic meal break scheduling. The violation rate at these locations is likely near zero. Including them in the population dilutes the violation rate for the high-violation locations while providing no meaningful data about the low-violation ones. Challenge: the population should be stratified by location or scheduling system.

02

Domain 2 — Sample Selection

Unstratified samples are vulnerable.

Under Duran, an unstratified sample that does not account for known sources of variation (location, shift, classification) may violate due process. If 60% of employees work at Location A and 40% at Location B, but the sample draws 80% from Location A, the results are biased. Push for stratification details.

03

Domain 3 — Violation Definition

The definition question is outcome-determinative.

An expert who defines every short meal punch as a violation (without accounting for waivers or employer rebuttal evidence) will produce a 35–50% violation rate. The same data, with waivers and rebuttal evidence considered, may produce a 15–20% rate. The difference is the entire case.

04

Domain 4 — Paid Premium Analysis

05

Domain 5 — Confidence Intervals & Extrapolation

Challenge the upper bound.

Plaintiff's experts typically use the upper bound of the confidence interval for the violation rate — maximizing the exposure estimate. The defense should argue for the midpoint or lower bound, supported by the employer's own records. If the full population data is available, argue that sampling is unnecessary — use the actual data.

06

Domain 6 — Affirmative Defense Accommodation

Duran requires individual defense opportunity.

The Supreme Court in Duran held that a class cannot be certified on the premise that the defendant "will not be entitled to litigate its statutory defenses to individual claims" (Duran v. U.S. Bank (2014) 59 Cal.4th 1). If the sampling expert's methodology forecloses the employer from presenting individualized defenses, the entire analysis may be inadmissible.