By Richard Wolf

WASHINGTON — The last of three major Supreme Court cases testing the legitimacy of class action lawsuits may produce an unlikely victory for labor over management.

The Supreme Court appeared Tuesday to side with workers at an Iowa pork processing plant demanding overtime pay for time spent putting on and removing sanitary and protective gear, even though their class action hinges on statistical averages rather than actual time records.

At least five justices expressed sympathy for the workers’ argument that since Tyson Foods kept no records of the time spent preparing for slaughter and processing assembly lines, they could rely on a 69-year-old Supreme Court precedent permitting such averaging.

The workers’ challenge was the third case to reach the high court during the past month pitting workers or consumers against companies in what often are multi-million dollar battles over class action lawsuits. Workers and consumers depend on such collaborations; businesses say they gloss over different grievances and grant awards even to those who were unaffected.

In each case, the justices agreed to hear petitions from companies seeking to overturn lower court rulings that allowed such lawsuits to proceed. Just by granting each case, the conservative-leaning court appeared to signal its intentions. But at Tuesday’s oral argument, Justice Anthony Kennedy and the court’s four liberal justices said Tyson Foods failed to make a convincing argument against averaging workers’ preparation time.

“I just don’t understand your arguments,” Kennedy told the company’s attorney, Carter Phillips. “The case has been argued on different theories at many points.”

Tyson Foods, one of the world’s leading producers of meat and poultry, is trying to knock down a class-action lawsuit filed on behalf of more than 3,300 current and former plant workers seeking overtime pay. Its claim that the workers don’t share enough common traits to sue as a class follows similar cases heard over the past month in which companies argued that consumers could not prove any injury or had been offered complete restitution.

Consumer and labor groups fear the court will follow its past example and rule for the companies in most cases. In 2011, the court backed Walmart in a class action lawsuit filed on behalf of 1.5 million female employees nationwide claiming pay discrimination. In 2013, it denied Comcast’s cable subscribers the right to sue as a class against alleged antitrust activities.

“The stakes for consumer and employment class actions are absolutely enormous,” says Paul Bland, executive director of the legal watchdog group Public Justice. “If the corporate defense side gets what they’re asking for, class actions involving privacy or violations of the wage and hour laws will shrink dramatically, and in many cases become impossible.”

The common issue connecting this term’s cases is what type of injury rises to the level of a lawsuit — in particular, one in which hundreds or thousands of people can join together. The question is important, because while plaintiffs stand to gain from jury awards that can reach into the millions or even billions of dollars, companies face potentially ruinous verdicts.

Tyson Foods, for instance, faces $5.8 million in damages under lower court rulings that it refused to pay workers at its Storm Lake, Iowa, processing plant overtime for the minutes they spend donning and doffing protective and sanitary gear and walking to their work stations. That’s a fairly small case; others waiting in the wings involve a $187 million verdict against Walmart and a $1.1 billion verdict against Dow Chemical.

For Walmart, the nation’s largest private employer, it’s a case of déjà vu after winning the larger case four years ago. “As Walmart’s experience illustrates, this is a critical and recurring issue,” it says in a friend-of-the-court brief.

Liberal interest groups fear the business-friendly court — at which the U.S. Chamber of Commerce and other industry associations enjoy winning records — could make it more difficult to prove race or gender discrimination or price-fixing based on statistical analyses.

“Tyson Foods and its allies are urging the court to issue a really broad ruling that would make it harder for injured persons to bring class actions,” says David Gans, civil rights director at the Constitutional Accountability Center. That, he says, could “close the courthouse doors on ordinary Americans.”

In winning lower court victories, attorneys for Tyson employees contended that the company had “plant-wide policies” against overtime pay for putting on and taking off uniforms and walking to and from work stations. Because the company did not keep time records for those activities, the employees cited studies estimating statistical averages, then computed those estimates into dollars.

Company lawyers argued against such a “trial by formula,” contending the Iowa workers had 420 different jobs and therefore could not have suffered the same injury as a result of the pay policy. Hundreds of them had no claim at all, the company said.

That argument rang true for some of the court’s conservatives, particularly Chief Justice John Roberts and Justice Samuel Alito. Roberts noted the original jury award was just half what the workers sought, possibly because “there’s no way to tell whether everyone who’s going to get money was injured or not.”

But Justice Ruth Bader Ginsburg said the differences between jobs and gear were not so great as to make statistical averaging unreliable.

“They weren’t all that different,” she said. “So in one case, one wore mesh aprons, and in the other case, rubber aprons. It didn’t seem to be that wide disparity.”