This month, the U.S. Supreme Court heard argument in a case that would seem to raise easy enough questions: When does an employee’s workday begin and end? What activities count as “work”? However, these questions have given way to tortured analysis and fairly arbitrary results.

Over the years, courts have ruled pre-shift and post-shift activities are compensable if they are “integral and indispensable” to the principal activity of the employment, whereas activities falling outside this definition are considered “preliminary” and “postliminary” and therefore not compensable. Of course, these definitions raise as many questions as they answer. What is “integral and indispensable”? What is the “principal activity of employment”? Not surprisingly, given this nebulous standard, court holdings vary widely even when fact patterns are very similar.

This convoluted analysis was on display October 8, 2014 in the U.S. Supreme Court, which heard oral argument on whether employee time is compensable when an employee stands in line for post-shift, security screening. In that case, the employees worked for a staffing agency and performed work at an Amazon.com warehouse, performing tasks such as filling customer orders and packaging them to ship.

The employees alleged that after they clocked out, they were required to undergo an anti-theft search and screening process that took up to 25 minutes because the employer set up just two screening checkpoints for a thousand workers. The employees claim they should be paid for time spent during the long screening process. The employer on the other hand argued that the law is already well established on this point: clocking out or waiting to clock out is not traditionally treated as compensable time, and there is no work being performed while employees are waiting in line to be searched.

Remember, the legal standard is whether the screening process is “integral and indispensable” to the principal activity of the employment. But during the oral argument, the Supreme Court justices seemed rather befuddled by this standard. Consider the following questions [edited, in part, to suit this article]:

Justice Ginsberg: Is it irrelevant that because there are not enough security checkers and because all the shifts get out at the same time, what could be five-minute process turns out to be 25 minutes (of the workers’ time), and 20 of those minutes allegedly would not occur if the employer had provided sufficient staffing?

Employer: We don’t think that allegation is relevant here. . . The pure length of time of something does not take it out of “preliminary” or “postliminary” activities.

Justice Sotomayor: What’s a principal activity? How is it defined? Because you still have to define what a principal activity is. . . . Isn’t a principal activity work that benefits the employer in some way?

Employer: . . . No, Justice Sotomayor. You have to look, is this a preliminary and postliminary activity. And if it is, then it’s presumptively noncompensable unless it’s integral and indispensable to a principal activity.

Justice Kennedy: Why isn’t the long line caused by very few checkers “for the benefit of the employer”?

Employer: It might be for the benefit of the employer in that set of circumstances, Justice Kennedy, but that doesn’t make it not postliminary and therefore compensable.

Justice Breyer: Indispensable. Indispensable. Hardly anything is indispensable. Where – where does that word come from? . . . I mean, it can’t literally mean indispensable, can it? Because anything at the end of the day, there’re probably five ways of doing it [so the selected way is not truly indispensable].

Employer: Egress security is not indispensable. You can perfectly well run a warehouse facility without egress security.

Justice Kagan: Actually, I don’t think you can. I mean what makes it Amazon? It’s a system of inventory control that betters everybody else in the business. And what’s really important to Amazon is that it knows where every toothbrush in the warehouse is. That’s just as integral to what Amazon does . . . as all the stocking and unshelving.

And that was just the Court’s questioning of the employer’s counsel. The justices were just as tough on the employee’s attorney. For example, when the employee’s counsel argued that exit screening was integral and indispensable to the principal activities of the job, Justice Roberts quipped, “Nobody hires a worker to go through a security screening.”

A link to the transcript can be found here. An audio summary with thoughtful non-lawyerly analysis is also available from NPR’s Nina Totenberg.

What should employers take from this issue currently pending before the Supreme Court and the Justices’ efforts to wade through it? Employers need to understand that the legal standard for defining “preliminary” and “postliminary” activities was developed in 1947 when the Portal To Portal Act was enacted. The American workplace has changed since then, and the 1947 law is not well suited to provide easy answers to many questions raised in 2014. As nine Justices struggle to make sense of this legal standard (decision expected by June 2015), employers would do well to audit and carefully consider any activities they require from non-exempt employees before or after the shift.