In those papers - a plea agreement for former Trump campaign foreign policy adviser George Papadopoulos - Mifsud is not named. But the Maltese national and London-based academic confirmed today that he is the "professor" who is mentioned in the probe.
According to the court files, the professor took an interest in Papadopoulous after the latter joined the Trump campaign. Mifsud promised him "dirt" on Hillary Clinton compiled by the Russians, including thousands of emails.
He also offered to serve as a go-between in Papadopoulos' efforts to connect the Trump campaign with the Kremlin, even going so far as introducing Papadopoulos to a woman he identified as Putin's niece.
Whether Mifsud really had the sort of Kremlin contacts that Papadopoulos claims he advertised is not known. But the question of how the Trump campaign regarded Mifsud's apparent approach, and whether it yielded anything substantive, could be a key focus of Mueller's investigation.
Mifsud, who is in his mid-50s, insisted that the claims embedded in the court documents are exaggerated, echoing points he had made months earlier in response to inquiries from the Washington Post.
"I have a clear conscience," Mifsud told the Daily Telegraph.
Mifsud told the Telegraph that he knew nothing about emails containing "dirt" on Clinton, calling the allegations upsetting. He also dismissed the disclosure that he introduced Papadopoulos to a "female Russian national," calling the allegation a "laughing stock."
In emails to the Post in response to questions in August, Mifsud had played down his connections to Moscow, insisting they were purely related to his work as a professor.
"I am an academic, I do not even speak Russian," he wrote.
But the details that emerged today based on interviews with those who know him, his writings and his travels suggested a more complex picture, one that better matched the image of the professor in court files as a somewhat obscure European academic who longed for more.
Hailing from the European Union's smallest nation - the Mediterranean island of Malta - he parlayed roles advising the Government there into top positions with educational institutions that have exalted-sounding names but are little-known even within academia.
Those included president of the Slovenia-based Euro-Mediterranean University and honourary director at the London Academy of Diplomacy.
His one-time assistant at the academy, Natalia Kutepova-Jamom, said he had set out in 2014 to build his contacts with Russian academics and policymakers.
She said that she booked her former boss a speaking slot in 2014 at the Sochi meeting of the Valdai Discussion Club, a Russian state-funded think-tank that is seen as close to the Kremlin, to speak on "economic and international cooperation".
Mifsud later suggested to her that he used those early contacts to open doors for higher-level meetings. But she was disbelieving when he told her last year that his contacts had reached all the way to Putin, with whom Mifsud claimed to have had "a short private meeting".
Kutepova-Jamom said she didn't believe the two met because Mifsud is "a too 'small-time' person" to meet with the Russian leader.
But Mifsud himself had written about being in the room with Putin to hear him speak at a 2015 event hosted by the Valdai Discussion Club, and reported that he had asked a question of Foreign Minister Sergei Lavrov.
In that piece, for Valdai's web site, he wrote approvingly of Russia's policy in Syria, saying Putin had "walked the talk". The US Administration of then-President Barack Obama, by contrast, was "on the defensive".
In a northern spring 2016 piece - around the same time he was allegedly meeting with Papadopoulos - he asserted that he knew "Russia quite well".
Online biographies present Mifsud as an authority in the field of international relations and diplomacy across Europe, the United States, Russia, Africa and the Mediterranean region. But his academic work in these areas appears limited. He has published in peer-reviewed journals on Maltese education policies.
According to a biography on the London Centre of International Law Practice's website, which was deleted on Monday, Mifsud "served prominently" in Malta's Ministry of Foreign Affairs and worked as an adviser for Malta's Ministry of Education.
Scotland's University of Stirling said in an emailed statement that Mifsud joined its politics department in May this year as a "full-time professorial teaching fellow".
Former colleagues said they didn't think of Mifsud as someone with any particular Russian expertise.
Nabil Ayad, who hired Mifsud as an honourary director at the London Academy of Diplomacy - where Ayad was founder and director - said Mifsud's focus was broadly in the area of diplomacy.
"As assistant to the Maltese foreign minister, he travelled to many countries and met many heads of state," said Ayad.
Ayad said the institution's work involved occasional trips to Moscow, including for collaboration with the Diplomatic Academy of the Russian Foreign Ministry.
"We tend to deal with governments, so I don't think he has any special connections or relationships," Ayad said. "If a meeting took place between a Russian official or he introduced someone, it must have been by chance, not by design."
But Mifsud had occasionally gone beyond the role of the typical academic. In 2015, he was an observer for elections in Kazakhstan that were sharply criticised by independent groups. Mifsud's take was far rosier, mirroring the Russian line.
The election, he told Kazakh media, was "consistent with all international norms".
"At many polling stations was an image that I associate with a family meeting," he reported.
Mifsud told the Telegraph that he introduced Papadopoulos to a programme director of the Russian International Affairs Council, a state-funded Russian think-tank that is close to the foreign ministry, and that he tried to set up meetings with experts on the European Union.
"We are academics," Mifsud told the paper. "We work closely with everybody."
He said that he met Papadopoulos in Italy in March 2016 and then 10 days later in London.
Mifsud's contacts in Moscow go back to at least 2012, when a delegation from Moscow State University's Faculty of Global Processes established a partnership with the London Diplomatic Academy, according to publications by the university faculty and a newsletter founded by order of the Russian Ministry of Foreign Affairs.
Between 2013 and 2017, Mifsud visited Moscow State University about once each year, giving lectures and posing for photographs with the department head, Ilya Ilyin.
The nature of the partnership was not immediately clear, although Mifsud had discussed exchange programmes and joint research projects. The department advertises itself as a stepping stone for graduates to work "in the Russian Government, the presidential administration, federal ministries and agencies, the special services," and outside of government, Alexei Andreev, the deputy director of the faculty, said in a promotional video.
Reached on today by telephone, Alexeev played down the department's ties to Mifsud.
"I think he is one of those people who has a lot of connections," he said.
