When it came to the character of witnesses upon whom he relied during his nearly two-year investigation, Robert Mueller clearly didn't discriminate. He even relied on a man convicted of child porn charges - Lebanese businessman George Nader - to give evidence against people in Trump's circle.

Now, Nader on Friday was indicted on new charges of importing child pornography and traveling with a minor to engage in illegal sexual activity, Politico reports.

Some of the charges stem from a search of Nader's iPhones that was conducted in April 2018, when he was detained and questioned by agents on behalf of Mueller after arriving at Dulles Airport.

It's unclear what Nader told Mueller, though it's believed his testimony pertained to actions by Erik Prince, the Blackwater founder and brother of Betsy Devoes, who Mueller alleged met with an ally of Russian President Vladimir Putin in the Seychelles around the time of Trump's inauguration. It was alleged that Prince was trying to set up a "back channel" to Trump. Nader is allegedly an emissary of the UAE.

Soon after the images were discovered, prosecutors reportedly filed a criminal complaint against Nader over the images, but they kept the charges under seal, and Nader's lawyers were never informed of his impending arrest all the while that he continued to cooperate with the Mueller probe.

That means that Mueller kept a suspected child abuser and pornographer on the streets while it used him as a witness. And now that Nader is no longer useful, he is finally being charged.

Nader was initially arrested on a criminal complaint last month after flying into JFK airport from an international destination, and he was, unsurprisingly, ordered held without bail. He was wearing an Alexandria jail jumpsuit during a five-minute hearing in US District Court in Virginia on Friday. She set a trial date for Sept. 30. Nader's lawyers stressed the fact that he cooperated with Mueller when asking that he be released on bail, but their requests were denied. They argued that he couldn't possibly pose a threat to children since Mueller allowed him to enter and exit the country multiple times while he was cooperating in the probe.

The Lebanese businessman has a shadowy record that includes a 1991 conviction on child pornography charges in the US - for which he served only six months in a halfway house thanks to his role in helping to free American hostages in Beirut. He has also been charged and convicted in the Czech Republic in 2002 on 10 cases of sexually abusing minors, and eventually received a one-year prison sentence.

None of this apparently phased Mueller.