Mitt Romney's call for Donald Trump to release his taxes has put the real estate developer on the defensive. After 48 hours of back-and-forth with Romney over Twitter, Trump was confronted with the issue during Thursday night's Republican debate. Were Romney's accusations that there's a "bombshell" in his returns actually true?, Wolf Blitzer asked.

Trump didn't say, no, choosing instead to say that Romney "looked like a fool" in 2012 by delaying on releasing his taxes. He then explained why he wasn't offering up his own.

"I want to [release them], except for many years, I've been audited every year," Trump said. "Twelve years, or something like that. Every year they audit me, audit me, audit me. Nobody gets audited -- I have friends that are very wealthy people. They never get audited. I get audited every year. I will absolutely give my return, but I'm being audited now for two or three years, so I can't do it until the audit is finished, obviously. And I think people would understand that."

Trump later suggested that he was maybe getting audited because he was a "strong Christian," a way of reinforcing his self-identification as a religious person and tapping into Republican anger over the IRS's targeting of conservative groups shortly before the 2012 election. It's clever political positioning, though the claim itself is highly (highly!) questionable.

So where does Trump's other claim fall, that he's audited all the time and that he can't release his returns as a result? To answer that, we reached out to an attorney who specializes in tax law, Steven Goldburd, partner at Goldburd McCone.

"Think of an audit as an investigation, an on-going investigation," Goldburd said. "Any person that has legal counsel, their legal counsel will say, 'If you're under investigation, you should not be talking to the media, you should not be talking to anyone other than your legal counsel or through your legal counsel.'" To use an analogy: If you're summoned to the police department as a potential suspect in a crime, it is not advisable to go in front of a camera and start talking about what did and didn't happen. Granted, an audit is a different beast than a criminal investigation, but it's still not advisable. "Until the investigation is concluded," Goldburd said, "he should not be releasing anything."

Goldburd also wasn't surprised that Trump might be audited regularly. "Millionaires as a whole get audited more often -- and are targeted more often -- because they have more ups and downs, more expenses, more things to consider than others," he said. He also noted that large businesses will sometimes preemptively reach out to the IRS to clarify components of the filing. "Someone in his position could be audited every year, and it could be that he's inviting the audit himself," Goldburd said.

If Trump doesn't want to release his tax returns -- which, let's be honest, is probably a fair assumption -- the good news is that there's no way of knowing how long this will take. Even if we knew how long the audit might take, we don't know when the audit began. "It could take anywhere between a few weeks to months and months," Goldburd said. That suggests that Trump has a ready-made excuse that could easily last through November -- at least for more recent years of filing.

But can't he release something, we asked? Nope. "I probably would not allow him to release anything," Goldburd said. "He's in the middle of an investigation."

Precisely the argument that Donald Trump is making.