Is Donald Trump right when he says Hillary Clinton deleted 33,000 emails? Yes and no.

About 30 minutes into Sunday night’s debate, Donald Trump jumped erratically from a bit of free association about Bernie Sanders and WikiLeaks to suddenly declaring he’d jail Hillary Clinton if elected president.

As Vox’s Zack Beauchamp notes, this was extraordinary: Calling for your political opposition to be locked up is an unprecedented act in modern American political history.

But what was Trump’s underlying charge, and does it make any sense? Trump claimed Clinton deserved to be thoroughly investigated — and elsewhere in the debate, jailed — because of the 33,000 emails she allegedly deleted in violation of a congressional subpoena.

Here’s Trump:

I didn’t think I’d say this, and I’m going to say it and hate to say it: If I win, I’m going to instruct the attorney general to get a special prosecutor to look into your situation because there’s never been so many lies, so much deception.

There has never been anything like this, where emails and you get a subpoena and after getting the subpoena, you delete 33,000 emails and then acid wash them or bleach them.

We should get the most important point about this out of the way: From what we know from the FBI, Trump’s accusation that is flat-out incorrect. FBI Director James Comey has repeatedly said that there’s “no evidence” Clinton’s emails were deleted in an attempt to hide them, and all of the documents released by the FBI’s investigation since then have backed that up that conclusion.

But like many wild accusations, Trump’s claim is built around a true fact: Somewhere around 33,000 emails from Clinton’s time as secretary of state really were deleted. Trump, however, omitted the most crucial fact about these emails — Clinton’s team ordered them to be deleted before any subpoenas had been issued.

The key to understanding what’s going on here is to first go back to why Clinton’s emails were deleted in the first place.

All of the emails Clinton sent or received while secretary of state were once being stored on one private server. When a congressional investigation into Benghazi began asking for records from her time as secretary of state, Clinton ordered her lawyers to give the State Department all of her “work-related” emails.

This is how we get to two separate batches of Clinton emails — the first “work-related” emails turned over to the state department, and the second “non-work related” emails that stayed on the private server.

That first batch of around 30,000 emails has been released piecemeal by the State Department. The second batch of “non-work related” emails, around 32,000 of them, were eventually deleted.

It’s for the deletion of this second group of emails that Trump thinks Clinton should be jailed. The idea, popular among some conservatives, is that Clinton ducked congressional investigators by deleting these private emails — which they think may have contained damaging Clinton secrets — while under subpoena.

This accusation is very difficult to maintain under the facts produced by the FBI for a few key reasons.

For one, Clinton’s staff told the contractor managing the private sever to delete the second batch of emails in December 2014, according to the FBI. The House Republicans’ Benghazi committee didn’t order that all emails on the private server be preserved until March 2015. (There’s a complicated counter-narrative that these emails weren’t actually deleted until a conference call with Bill Clinton’s attorneys after the subpoena was issued, but that story doesn’t make much sense for reasons I explained here.)

It’s also not really possible to think that Clinton herself is responsible for hiding and deleting the “non-work related” emails that Trump is referencing. That’s because Clinton delegated those decisions to her attorneys — nobody has claimed that Clinton herself determined which emails were work-related and which ones were not.

But, for the sake of argument, forget the timeline and forget the fact that Clinton herself wasn’t actually involved in the determination of which emails should be turned over. Most tellingly of all, Clinton had the legal authority to classify as private and delete whichever emails she felt was appropriate.

“There is no question that former Secretary Clinton had authority to delete personal emails without agency supervision — she appropriately could have done so even if she were working on a government server,” said attorneys from the Justice Department, according to CBS News.

Perhaps you can look at the sources I’ve quoted here — the FBI, the Justice Department, the State Department — and assume they’re all in Clinton’s pocket and therefore can’t be trusted on this question. But if that’s your starting point, there’s not much the press or Clinton herself can say to convince you otherwise.