With the news that Donald Trump’s Justice Department targeted communications and other records of Democratic members of Congress, as well as their aides and even family members, forcing Apple to hand over metadata on no less than two Democratic members of the House Intelligence Committee and gagging the tech giant from disclosing that, Rep. Adam Schiff called for an investigation into what he called a “terrible abuse of power.”

The investigation really needs to answer only one question: Were Republicans targeted as well? That’s it. It’s the only question that really matters.

If Republicans were also targeted, then this could still have been a purely political investigation, depending on other facts. But if Republicans were not targeted, then that should be the end of the inquiry, at least as far as the public is concerned. If Trump’s DOJ targeted only Democratic lawmakers, that’s a politically motivated investigation—even if there is some arguable criminal activity afoot.

Perhaps confusingly, even if the investigation was politically motivated, it is legally valid so long as there is at least probable cause that a crime was committed. The Supreme Court has suggested since at least 1996 that an investigation motivated by a bad reason is not invalidated if there is substantial evidence of an objective violation of the law. Legally, it’s fine for police to stop only Black drivers and spare white drivers, so long as the Black drivers have committed traffic violations.

It follows that Trump’s DOJ could legally justify their investigation of only Democrats if they have enough evidence of criminal leaks by Democrats. In fact, even if the DOJ had evidence of Democrats and Republicans alike committing criminal leaks, the DOJ would technically, legally be permitted to choose to investigate only Democrats. There’s not much to stop a politically motivated Attorney General who sees criminal activity from two parties choosing to only investigate one of them.

But legal justification is not the same as political and moral justification, and answers are coming. The Justice Department’s Inspector General has announced an investigation into the subpoenas and the reasons they were issued. Plus, the DOJ is under new management, by a new President and a new A.G. It’s a Justice Department that will surely be more transparent to an inquiry about the former administration’s investigation decisions. A Merrick Garland-led DOJ isn’t necessarily looking to smear Trump. But let’s be candid: the president and the AG won’t be personally devastated if this reflects poorly on Bill Bar and the ex-president.

But isn’t that more of the same problem? If the current DOJ is more aligned with the Democrats whose privacy was invaded, won’t Biden’s DOJ be more likely to help those Democrats conclude they were targeted by Trump’s DOJ?

Ideally, that’s what the Inspector General’s Office is for: an independent, nonpartisan investigation of the reasons for the initial investigation.

The election was several months ago, but imagine the alternative: if Trump had been elected to a second term, Apple might have disclosed this information with a Trump appointee heading the DOJ. The affected Democrats might have been demanding transparency from a Trump DOJ trying to indict them.

That’s a hypothetical now, but the IG’s real-world investigation is expected to be far-reaching. For many, it just needs the answer to one question.