The trove of files from the Panama Papers and Paradise Papers leaks exposed the secret offshore financial dealings of the global elite. Digging through terabytes of data to unravel those secrets were hundreds of reporters led by Marina Walker Guevara. The Pulitzer-Prize-winning journalist talks to Fraud Magazine about managing international news media collaborations, data investigations and the urgency for stories that hold the powerful to account.
Journalism generally isn’t a team sport. For most reporters, the job is about getting the scoop, publishing an exclusive, reporting a beat, having a byline — terms that suggest a lone professional obtaining information before anyone else and keeping it confidential until it’s time to file the story.
But say you’re a reporter looking at 2.6 terabytes of data sent to you from an anonymous source. Within that data is information about the secret financial dealings of the world’s most powerful people. These powerful people own offshore accounts often parked in sun-soaked island tax havens for the benefit of avoiding taxes or concealing ill-gotten gains. You might need the help of an entourage of journalists, working in different countries, who can sort through all those financial documents connected to the elites — and criminals — of their respective countries.
Of course, collaboration on a global scale requires immense coordination skills and the technological know-how of an experienced investigative journalist who can lead that team of reporters from different backgrounds and varying goals to deliver stories of public importance.
Marina Walker Guevara was the journalist for that mission. More than nine years ago, as deputy director for nonprofit news organization, The International Consortium of Investigative Journalists (ICIJ), she brought together and managed hundreds of journalists across the globe who collaborated for more than a year to investigate the leaked data files known as the Panama Papers. The massive collaboration exposed the secret financial world of the wealthiest 1%, led to the resignations of some politicians and helped law enforcement track and trace fraudsters, drug dealers and arms traffickers.
“We don’t become journalists because we want the world to stay the same. We want to see change in the world,” Walker Guevara said in an interview with Fraud Magazine. “That’s why we invest months and months collaborating with one another, digging up data and doing really dangerous things.”
Walker Guevara, who’s currently the executive editor of the Washington D.C.-based Pulitzer Center, talks to Fraud Magazine about how she and hundreds of journalists combined their investigative powers to reveal the clandestine world of offshore companies. The Pulitzer Prize-winning journalist also explains how data and artificial intelligence can be used to tell stories and how journalistic collaborations and public interest reporting are needed now more than ever.
Radical sharing
When Fraud Magazine met with Walker Guevara over a Teams video chat, it had only been a couple weeks since the White House barred an Associated Press (AP) reporter from Oval Office press briefings. The news service chose to adhere to its style guide and refer to the body of water along the southeastern periphery of the U.S. as the Gulf of Mexico. In February, President Donald Trump issued an executive order to rename the Gulf of Mexico to the Gulf of America. Even though the AP regained its access to White House press briefings, it seemed appropriate to ask an investigative journalist how to report the news when information is difficult to obtain.
Walker Guevara says the job requires “radical sharing.” Instead of journalists competing against one another for scoops and exclusives, journalists work together to obtain information.
“I lean into my work at the International Consortium of Investigative Journalists,” she tells Fraud Magazine. “When you’re facing a complex story in a difficult environment, we need to lean on each other and work collectively.”
She explains that journalists now have access to methodologies and technologies for sharing data and collaborating on investigations. These tools can help journalists communicate and safely exchange information.
“What we need to do now is double down on these efforts,” she says. “Right now, there are huge stories that not one single reporter or media organization will be able to tackle on their own. There are systemic issues that are profound, complex and dangerous to cover.”
“Now more than ever, we need to go beyond scooping, go beyond trying to get ahead individually or as one major organization and think systemically.”
She reflects on the work she did with the Panama Papers and Paradise Papers and how those collaborations included the help of accountants, fraud examiners, lawyers and data analysts — professionals who could decipher the financial documents from the leaks.
“We’re the ones to develop new methodologies that allow us to tackle big amounts of data, make sense of it and find the stories of public interest that need to be urgently told.”
So how does a journalist convince their colleagues to forgo personal ambition and work together?
“We start by understanding what motivates a group of people,” says Walker Guevara. “In the case of journalists, what motivates them is a story.”
The Panama Papers and Paradise Papers leaks were stories with data and documents that “revealed something unknown and revealed a system that might be harming a lot of people,” according to Walker Guevara.
“The first thing we do to convince journalists to work together is to go to them with a really good proposal, with a really good story.”
She explains to Fraud Magazine that in developing storylines to present to fellow journalists, you first must consider the documents and data to collect and analyze together. “We then go to our colleagues with a well-defined and interesting framework, and you tell them that you have documents. They’re probably going to jump on it, even if they could’ve gotten those documents on their own. Sometimes we need somebody to organize us and bring it all together.”
Luckily, Walker Guevara had documents that were “revelatory and important.”
Names and numbers
Walker Guevara’s boss at the ICIJ would frequently visit her office during the Panama Papers investigation with a not-so-subtle reminder of its weighty consequence. “He would just casually walk into my office and say, ‘Remember that everything hangs on one error,’” she recounts to Fraud Magazine. “If we have one error, the whole thing collapses, because it was the first time we were doing this large-scale global collaboration. There was a lot at stake.”
“If we had gotten one name wrong because we didn’t do enough due diligence, imagine what a disaster it could have been, and not only for the person who gets wrongfully accused of something,” Walker Guevara tells Fraud Magazine. “It could have hurt the entire investigative journalism movement.”
The story of how the Panama Papers leak, and later, the Paradise Papers leak, became an international sensation is well-known to many all over the world by now. In 2015, Bastian Obermayer, a journalist for German daily news publication, Süddeutsche Zeitung, received an electronic file from an anonymous source known only as “John Doe.” Those files, according to John Doe, were internal documents from an obscure law firm based in Panama, called Mossack Fonseca. What Mossack Fonseca lacked in name recognition it made up for in being a prolific provider of offshore financial services to the world’s rich and famous. The little-known law firm would soon enough become notorious.
Obermayer, along with his colleague, Frederik Obermaier, would turn to the ICIJ for help. As Obermayer told Fraud Magazinein a 2019 interview, there weren’t many German stories in all those documents, but there were plenty for an international audience. And the two German reporters didn’t speak the languages many of the documents were written in. Walker Guevara marshaled the global reporter reserves to assist the German journalists in the investigation. More than 370 reporters hailing from nearly 80 countries across six continents, representing 100 news organizations, were involved in the year-long Panama Papers excavation.
In April 2016, the ICIJ released the results of the year-long investigation with a searchable database. Even today, journalists and law enforcement around the world use it as part of their investigations. (See sidebar “Nine years later, the Panama Papers leak is still generating stories,” at the end of this article.)
Then in 2017, the ICIJ released another tranche of files, again courtesy of John Doe. This time the treasure trove contained 13.4 million documents, further revealing the secret financial dealings of world leaders, celebrities and corporations. Most of the documents came from offshore legal services provider Appleby and Singapore-based corporate services firm Asiaciti Trust. Because many of the documents concerned offshore accounts located in tropical places like the Bahamas, the leaks were dubbed the Paradise Papers. The French term for tax haven is paradis fiscal (financial haven).
If we have one error, the whole thing collapses, because it was the first time we were doing this large-scale global collaboration. There was a lot at stake.
People protested around the world after learning how the rich and powerful hide their money, avoid paying taxes and conduct shady business deals. Some world leaders were even forced to resign, including the prime minister of Iceland. Documents in the leaks revealed that the prime minister and his wife secretly owned a company in the British Virgin Islands. Former U.K. Prime Minister David Cameron admitted that he profited from an investment fund his father created. The fund was incorporated in Panama but managed in the Bahamas. The documents also showed that Russian President Vladimir Putin’s associates funneled $2 billion through shadow companies.
We don’t become journalists because we want the world to stay the same. We want to see change in the world.
Marina Walker Guevara
From the Paradise Papers, the public learned that then-U.S. Commerce Secretary Wilbur Ross had a stake in a shipping company that received more than $68 million from a Russian energy company co-owned by Putin’s son-in-law and that former Canadian Prime Minister Justin Trudeau’s chief fundraiser had secret deals. The public learned about the British royal family’s offshore holdings.
The Paradise Papers include information about Microsoft co-founder Paul Allen’s submarines. Pop star Madonna owned shares in a medical supplies company, and Paul Hewson, better known as Bono, lead singer of rock band U2, owned shares in a Lithuanian shopping center.
The ICIJ, along with Walker Guevara, Obermayer and Obermaier won the Pulitzer Prize for Explanatory Reporting in 2017 for their work on the Panama Papers investigation. Obermayer was the recipient of the Association of Certified Fraud Examiners’ (ACFE) Guardian Award in 2019. Walker Guevara will receive the 2025 Guardian Award at the 36th Annual ACFE Global Fraud Conference in Nashville, Tennessee. The Guardian Award is presented each year to a journalist who has exposed financial crime and contributed to the worldwide effort to prevent and detect fraud.
Paradis fiscal
As Walker Guevara told Fraud Magazine, journalists are driven by making an impact, and the Paradise Papers and Panama Papers investigations certainly made one. The investigations showed how law-abiding people and criminals alike exploit secretive offshore companies. They revealed that where tax havens are concerned, it doesn’t matter if someone is a criminal — they can still obtain a shell company located in a territory with rules that stymie law enforcement efforts to trace illegal assets.
The investigations revealed a shadowy world of law firms and banks that “sell financial secrecy to politicians, fraudsters and drug traffickers as well as billionaires, celebrities and sports stars.”
Even some of the most prominent anti-corruption proponents around the world were discovered in the leaked files. For example, reporters were able to link offshore companies to the family of China’s President Xi Jinping. Xi has spoken publicly about fighting “armies of corruption.”
Owning an offshore company is legal, and in some cases, there are good reasons for having one. For example, Businesspeople in authoritarian regimes might use them to protect their money from being seized by the government. People might also use them for inheritance and estate planning. But, as the ICIJ reported, offshore providers often fail to do their due diligence to ensure that their clients aren’t involved in criminal activity or evading taxes. Offshore companies provide secrecy to clients, which is why corrupt politicians, money launderers, drug dealers and fraudsters use them.
Perhaps the greatest impact of the Panama Papers was how it revealed inequalities created by the offshore system. At a meeting of the World Bank and International Monetary Fund in 2016, World Bank President Jim Yong King remarked, “When taxes are evaded, when state assets are taken and put into these havens, all of these things can have a tremendous negative effect on our mission to end poverty and boost prosperity.”
In the weeks following the Panama Papers revelations, Algeria opened a probe into a corporate leader suspected of money laundering. The United Kingdom recovered hundreds of millions of dollars in taxes. And, according to the ICIJ, Colombia was able to double its tax revenue collection. The CBC reported in April 2025 that two dozen tax agencies around the world have collected nearly $2 billion in tax arrears and fines because of information from the Panama Papers leaks.
In February 2017, Panamanian investigators arrested Mossack Fonseca founders Ramón Fonseca and Jürgen Mossack on charges of money laundering. While their law firm was dissolved in 2018, the pair were acquitted of all charges in 2022. Last April, a Panamanian court acquitted all 28 people who’d been accused of setting up shell companies connected to bribery and corruption scandals in Brazil and Germany.
Two countries, one company
Walker Guevara tells Fraud Magazine that where she grew up in Mendoza, Argentina, the stark contrasts of social inequality were obvious. “At the same distance from my house there were impressive mansions and slums with no running water or paved streets.” Growing up against that backdrop filled her with questions about why such inequality exists.
“I found in journalism an opportunity to ask those tough questions, find answers for people and share those answers in ways that could inspire people and move them to action.”
In the early days of her career, Walker Guevara was a daily reporter but grew tired of the immediacy of daily news coverage. She moved on to a Sunday reporter position. “I had seven days to work on a story; it was a luxury to go in depth on different stories.”
The ability to focus deeply on a story led her to investigative reporting, but this was a complicated job in Argentina. “It was a time when we didn’t have a Freedom of Information Act, so it was hard to find documents, and everything had to be worked through sources,” Walker Guevara tells Fraud Magazine.
She says that she’d always admired American investigative journalists and wanted to learn from them, so she joined an exchange program with the Philadelphia Inquirer.
During her six months at the Philadelphia Inquirer, she met many reporters who’d graduated from the University of Missouri’s journalism school. The university, located in Columbia, Missouri, has long been considered a top journalism school. It’s also home to the nonprofit organization, Investigative Reporters and Editors (IRE). Walker Guevara became a graduate student at University of Missouri’s journalism program and worked for IRE.
It was during her time as a graduate student that she’d break a story about a U.S. lead smelter operating in the Peruvian town of La Oroya nestled in the Andes. The company, Doe Run, greatly damaged the town’s environment, and at one time 99% of the town's children showed high levels of lead in their blood. Lead poisoning causes behavioral problems in children and slows growth. It can also cause neurological impairments and kidney damage. Extremely high levels may also cause seizures and death.
Doe Run was based in Herculaneum, Missouri. The smelter had moved some of its operations to La Oroya after the Environmental Protection Agency (EPA) fined it for violating environmental laws in the southeastern Missouri town. “I came across the story of Doe Run because of all the problems it had caused to the Herculaneum residents and how the EPA had cracked down on the company,” she explains. “I wanted to know what was going on with Doe Run in Peru.”
After a little bit of research, Walker Guevara learned that 99% of children in La Oroya had high levels of lead poisoning. “When you see a number like 99%, you cannot pass on that story.”
Walker Guevera spent two weeks on the ground in La Oroya, reporting and talking to residents. She reviewed documents and made several freedom of information requests in Peru, which allowed her to see Doe Run’s inspection records. “I was able to compare what Doe Run was saying versus what the inspection records were showing about the levels of metals it was actually releasing into the atmosphere.”
The resulting expose of Doe Run’s environmental degradation of La Oroya, “Children of Lead,” had a resounding impact. The company was eventually forced out of Peru. Walker Guevara was honored for her work on the story in 2005 with the Overseas Press Club Foundation scholarship.
“There was there was a flurry of coverage that came after that, which is what you want,” she tells Fraud Magazine. “You reveal the truth, and then you want your colleagues to keep the pressure on and keep reporting.”
Later, she’d join forces with St. Louis Post-Dispatch reporter Sara Shipley Hiles on an in-depth story about how Doe Run had been failing on its commitment to clean up La Oroya and run a clean operation there. The two reporters discovered that money meant for Doe Run’s remediation plan was going to its shareholders. The story “Lead Astray” was published in Mother Jones magazine in 2006. Walker Guevara and Hiles were awarded the In-Depth Reporting Award from the InterAmerican Press Association for the story. “That story really stayed with me because it was my first cross-border collaboration. It provided a model for me to follow later on at the ICIJ,” she says.
But the Doe Run story didn’t just serve as a model for what she’d later do with her work at ICIJ. It was through her work on the story that she learned about the investigative reporting organization. She applied for an internship but was initially rejected for being overqualified. A professor at the University of Missouri vouched for her, and she was hired as an intern. She stayed for 14 years.
Using machine learning to investigate the Panama Papers leak
In 2018, Walker Guevara left the ICIJ for Stanford University’s John S. Knight Journalism fellowship program. During the yearlong program, she studied how journalists may use machine learning, a field of artificial intelligence (AI), in their investigations. Since then, she’s become an advocate for journalists using AI for data-driven investigations. According to Walker Guevara, AI can help reporters pinpoint patterns in data, reduce the time it takes to find information and discover things they don’t know.
She also contemplates what the Panama Papers investigation would’ve been like if the global team of journalists had used artificial intelligence to dig through 2.6 terabytes of data.
In a March 2019 article she wrote for the ICIJ, Walker Guevara wondered, “What would our research look like if we were to deploy machine learning algorithms on the Panama Papers? Can we teach computers to recognize money laundering? Can an algorithm differentiate a legitimate loan from a fake one designed to shuffle money among entities? Could we use facial recognition to more easily pinpoint which of the thousands of passport copies in the trove belong to elected politicians or known criminals?”
Panama Papers investigators used technology to search through the leaked files. They used open-source data mining technology and graph databases. Technology helped them filter and organize data. Still, Walker Guevara wrote for ICIJ, “The great majority of the thinking in that equation were the journalists … Everything else came down to what those 400 brains collectively knew and understood about the characters and the schemes, the straw men, the front companies and the banks that were involved in the secret offshore world.”
Walker Guevara explains how technology could help journalists search emails. “Emails are a great source of information,” she said. “In this case, we had a lot of email communications, but they were a mess.”
"If you want to look at emails from one person, you’ll ask the system to collect all the emails from that one person. You’ll ask the system to show you that person’s email organized by date, then ask for their emails with attachments or emails with loan agreements attached. “It parcels the information in quite helpful ways,” she explains to Fraud Magazine. “You go from a universe of trillions of documents to one person’s inbox with loan agreements.”
During the Paradise Papers investigation, Walker Guevara says they were able to implement some machine-learning training. In her example for Fraud Magazine, she goes back to loan agreements. “If you want to focus only on loan agreements for the entire dataset, you train the machine on what a loan agreement looks like.”
But not all loan agreements look the same. They look different depending on the loan company, and they aren’t all in the same language. You go back to the machine and train it to find all those different types of loan agreements.
As Walker Guevara explains, you’ll still get false positive, but you’ll also be able to retrieve a lot of information that you wouldn’t be able to obtain by typing “loan agreements” into a search engine.
Once they had the data they were looking for, they’d consider whether there’d be enough public interest in that information. Then they’d consider the countries and journalists they’d need to work with to report on the story about people in the documents.
“These people might not be in the news all the time, but they’re connected somehow, and they’ve done something that is of public interest.”
Jennifer Liebman, CFE, is editor-in-chief of Fraud Magazine. Contact her at jliebman@ACFE.com.
This article was updated from the original published May 1, 2025.
The Panama Papers leak launched many stories about financial dealings that wealthy and powerful people had meant to keep secret. Nine years after the initial publication of the Panama Papers, investigators are still finding stories to tell.
Two of those stories concern government collapse in Bangladesh and one of the largest criminal organizations in Brazil.
In January, Tulip Siddiq resigned from her position as the U.K.’s economic secretary. News reports questioned whether she’d benefited financially from her relationship with her aunt, the former prime minister of Bangladesh, and whether Siddiq lived in several London properties connected to her aunt’s political allies. The Sunday Times found a link between Siddiq, a property and two offshore companies in the Panama Papers database. In August 2024, Sheikh Hasina, Siddiq’s aunt, fled Bangladesh when her government collapsed amid student protests. Bangladesh’s Anti-Corruption Commission is investigating allegations that Hasina and her political allies embezzled billions of pounds as they fled and used some of that money to buy properties.
Last October, the International Consortium of Investigative Journalists reported that police in Brazil uncovered a link in the Panama Papers between an alleged money launderer and one of the country’s largest criminal organizations. According to police, proceeds of drug trafficking were funneled through a number of companies set up to hide the illicit funds. One of those companies was registered in the British Virgin Islands by none other than the now-defunct Panamanian law firm Mossack Fonseca.
