This Tuesday, a skeptical Supreme Court heard arguments in the largest employment discrimination case in history. While several of the justices expressed concern over how such a large case could be effectively administered, one of the female employees’ lawyers may just have dealt the case a fatal blow.

Wal-Mart v. Dukes has been ongoing for over a decade, and the Supreme Court is currently reviewing whether nearly 1.5 million women at Wal-Mart have enough in common to be joined together in one giant class-action suit.

The suit, as I explained in a blog post on Monday, rests largely on 120 statements of anecdotal evidence, statistics on gender gaps in pay and promotion, and a statement by a Chicago sociologist on implicit bias. The statement on implicit bias is the glue that supposedly holds all these women together.

A corporate policy of discretion by store managers in regard to hiring, pay, and promotion decisions, supposedly enabled individual managers to express implicit biases against women, leading to statistical wage and promotion gaps by gender.

As Lyle Denniston writes on the SCOTUS blog:

It took only a few minutes of argument [Tuesday] by a lawyer who sued discount retailer Wal-Mart over the way it allegedly treats its women workers for a potentially fatal flaw in that case to stand out boldly.  It was what Justice Anthony M. Kennedy called, simply, an “inconsistency,” but it clearly could scuttle the entire idea that some 500,000 female employees can combine their challenge to the company into one massive case.

A basic claim of the case – absolutely vital to it, it seems – is that Wal-Mart has a policy of maintaining a common “culture” (the “Wal-Mart Way”) that ensures uniformity throughout its thousands of stores, yet company headquarters gives its local store managers unlimited discretion to decide workers’ pay and promotions, and the two together result company-wide in lower pay and fewer promotions for female employees.  As a logical proposition, that may seem somewhat self-contradictory, and that was exactly Kennedy’s point.  And his vote would seem to be a crucial one, given how other Justices reacted.

This case rested on very thin ice before, but Joseph M. Sellers, the plaintiffs’ lawyer, just put a deep crack in it. As Carrie Lukas explained in her Corner piece Monday:

The anecdotal evidence seems particularly weak in a case like this. …

Statistics about earnings are also notoriously misleading. …

Similarly, Walmart managers [may] have “implicit biases,” but what should count are the actions that they take. 

If the case were to succeed as a class-action lawsuit, it could open a Pandora box of liability, which could significantly backfire on working women. Thankfully, the Supreme Court seems to agree that the class-action claim rests on weak evidence.