Bill Gates, the co-founder of Microsoft and one of the world's most prominent philanthropists, is set to be interviewed by a congressional committee on Wednesday about his past association with the late convicted sex offender, Jeffrey Epstein.

Gates is appearing voluntarily in Washington, saying he welcomes the opportunity to answer questions about his relationship with the disgraced financier before the House Oversight Committee.

Epstein killed himself in a jail cell in 2019 while awaiting trial. His long-time friend and associate, Ghislaine Maxwell, is serving a 20-year prison term for her part in his crimes.

Gates's connection to Epstein came to wider public attention after the US Department of Justice (DOJ) recently published more than three million pages of documents linked to the criminal investigation of Epstein. Gates's name appeared thousands of times.

He has repeatedly denied any wrongdoing and rejected the idea that he knew anything about Epstein's illegal activity. But in a TV interview earlier this year, he did acknowledge he exercised poor judgement in meeting Epstein.

"I was foolish to spend time with him. I was one of many people who regret ever knowing him," he said.

Among the material released by the DOJ was a photograph that appears to show Gates near an aircraft with Epstein's pilot present. Gates has said he travelled with Epstein on a private jet - one of those facts that have haunted many who have been tarnished by Epstein.

Other images show Gates posing with his arm around Epstein and a number of unidentified women.

Documents also include draft emails attributed to Epstein, containing a series of unverified and disputed claims about Gates's personal life. These include allegations that Epstein facilitated "illicit trysts" with "married women" for Gates, that the Microsoft co-founder had contracted a sexually-transmitted infection (STI) from what Epstein called "Russian girls", and that he had "helped Bill get drugs" to treat it.

A separate email alleged that Gates sought to "surreptitiously" give his then-wife Melinda antibiotics to protect her from the same infection. Gates strongly denies these claims but has admitted having had affairs with two Russian women.

So, what are three big questions Epstein could be asked by the congressional committee?

Gates's core explanation for his association with Epstein has been that the relationship was transactional, centring on discussions about philanthropy and potential funding for his foundation that ultimately came to nothing.

It's not clear from his public statements what specifically brought the two together.

According to Gates, their association began in 2011 โ€“ three years after Epstein was convicted in Florida on two charges of soliciting prostitution, including one involving someone under the age of 18. The two still had dealings in 2014 โ€“ a long time, some might say, to discover Epstein wasn't providing any useful assistance for the foundation.

The lead Democrat on the committee, Robert Garcia, told reporters on Monday: "Bill Gates was still communicating with Jeffrey Epstein, even after some of this kind of horrific information about him and what he was doing was public to a lot of folks, and so we want to ask Mr Gates, why continue that relationship?

"Who else did he see? What else might he know? And who else should we be bringing in to ask questions of?"

Gates told staff at his foundation in February that he said he was aware of some "18-month thing" that had limited Epstein's travel, but that he didn't properly check his background.

That account is likely to be tested in questioning by the committee.

Lawmakers are expected to probe how plausible it is that Gates โ€“ one of the titans of the information sphere - would have remained largely incurious about the details of Epstein's background, including facts that were already in the public domain, during a period when the two men appeared to spend significant time together.

In its letter inviting Gates to sit for an interview, the committee said it believed he would have useful information concerning the "ways in which Mr Epstein and Ms Maxwell sought to curry favor and exercise influence to protect their illegal activities".

This at least is a possible reason for Epstein wanting to know someone like Gates - who, while not a politician, is a global figure with significant networks and influence.

The committee's point here suggests that Epstein wasn't just looking for powerful friends, but also ways of leveraging those contacts for other, illicit reasons.

It's clear Epstein appeared to spend a lot of time cultivating such people. His associations often blurred the line between business and social interactions.

He also kept copious and documented records of the people he knew: hence the piles of emails, photos and other documents that are now in the public domain.

He entertained, wined and dined, and flew people around for vacations at his various properties. It is plausible that some of the details he hoarded about his associates could have been used to pressure or influence them, though there is no evidence that this occurred in Gates's case.

Nonetheless, details about the alleged STI - denied by Gates - would certainly have the potential to be deeply embarrassing and damaging if Epstein had decided to use them.

"We want to know whether Epstein wanted to influence Gates or even whether he blackmailed Gates in any way like he allegedly did with others," Congressman Suhas Subramanyam, another Democrat on the committee, told the BBC.

From Gates's point of view, his stated motivation was raising money for his global health initiatives. Earlier this year, the Gates Foundation said: "On the basis of Epstein's claims that he could mobilise significant philanthropic resources for global health and development, a small number of foundation employees interacted with Epstein to try to secure this potential funding."

But, it added, "ultimately, the foundation did not pursue any collaboration with Epstein and no fund was ever created". It went on to say that it "regrets having any employees interact with Epstein in any way".

So it comes down to this: why spend so much time with someone who wasn't delivering? That will most certainly be a central question on the lips of those who will get to quiz Gates.

Additional reporting by Cai Pigliucci and Daniel Wittenberg

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