U.S. District Judge Ana C. Reyes said Littlejohn deserved the maximum sentence she could impose, because he had targeted a sitting president and thousands of others. Prosecutors said Littlejohn had disclosed the tax returns of about 7,600 individuals and 600 entities.

After comparing Littlejohn to the rioters who stormed the Capitol on Jan. 6, 2021, Reyes said judges had to send a message that “open season on our elected officials” would not be tolerated and that “an independent and steadfast judiciary stands ready to punish anyone who holds his personal political beliefs above the law.”

“Let me be absolutely clear: What you did, in targeting the sitting president of the United States, was an attack on our constitutional democracy,” the judge told Littlejohn. Regardless of how many people may consider Littlejohn a hero, Reyes said, “I want you to know that I am not one of them.”

Jonathan Jacobson, one of the federal prosecutors at Monday’s hearing, said “the tax returns are just the tip of the iceberg.” Littlejohn also leaked other sensitive financial information submitted to the IRS by some of the wealthiest Americans, including details on investments, stock trades, gambling winnings or audit determinations for a total of about 18,000 individuals, prosecutors said.

Only 152 victims have had their information included in online reports, leaving the others to wonder if their data will be publicized in the future, according to U.S. officials.

In brief comments to the judge, Littlejohn said, “I alone am responsible for this crime.” He said he wanted voters to be able to review Trump’s tax returns before the 2020 presidential election, and that he knew he would be held accountable in a courtroom one day for leaking the data.

Neither the Justice Department nor Littlejohn’s attorneys have named the private company where he worked at the time of the breaches. However, in a newsletter published in 2008 by the economics department of the University of North Carolina at Chapel Hill, which Littlejohn had attended, he wrote that he joined the consulting firm Booz Allen Hamilton after graduating in 2007 and that his work there involved the IRS.

In response to questions from The Washington Post, a spokesperson for Booz Allen Hamilton said: “We condemn in the strongest possible terms the actions of this individual, who was active with the company years ago. We have zero tolerance for violations of the law and operate under the highest ethical and professional guidelines. We fully supported the U.S. government in its investigation into this matter.”

In legal filings, Justice Department officials described how Littlejohn closely studied the IRS systems he would later breach with sophisticated digital techniques meant to hide his tracks. Rather than entering search terms such as “Trump” into an agency database, Littlejohn used broad parameters “designed to conceal the true purpose of his queries,” U.S. officials said. Littlejohn learned that IRS protocols could block large downloads from the agency’s systems, but in November 2018, he “exploited a loophole” by sending the data he found to a private website he had set up, according to the Justice Department.

He then transferred the data onto portable storage devices, including an Apple iPod he had outfitted as a personal hard drive, prosecutors said. For the ProPublica leak, Littlejohn uploaded reams of tax information to a private website using “two virtual machines (essentially simulated versions of physical computers),” which he destroyed shortly after the data transfers, according to prosecutors.

Littlejohn “weaponized his access to unmasked taxpayer data to further his own personal, political agenda, believing that he was above the law,” prosecutors in the Justice Department’s Public Integrity Section wrote in a legal brief, requesting that he receive the maximum prison term of five years.

“A free press and public engagement with the media are critical to any healthy democracy, but stealing and leaking private, personal tax information strips individuals of the legal protection of their most sensitive data,” Jacobson and prosecutor Jennifer Clarke wrote. “Everyone is entitled to equal protection under the law.”

Defense attorneys for Littlejohn requested a prison term of eight to 18 months, arguing that his offenses were “the product not only of his misguided idealism but of life experience that led him to treat each day as if it were his last,” including the death of his younger sister in 2013 and his father’s disease diagnosis in 2019.

The attorneys wrote that after leaking Trump’s tax data to the Times, but before his disclosures to ProPublica, Littlejohn was deeply influenced by “The Triumph of Injustice: How the Rich Dodge Taxes and How to Make Them Pay,” by economists Emmanuel Saez and Gabriel Zucman.

“The 2019 book set forth a systematic analysis of the U.S. tax system, concluding that for the first time in a century, billionaires almost universally paid lower effective tax rates than the average American taxpayer,” attorneys Lisa Manning and Noah Cherry said in a court filing.

But they added that Littlejohn soon came to regret his actions and, once he was under investigation, spoke to a federal watchdog agency, the Treasury Inspector General for Tax Administration, about ways to “better detect and deter future theft and illegal disclosure of IRS data.”

“He originally acted out of a sense of moral duty, but soon came to understand that his conduct was morally wrong,” Manning and Cherry wrote. “Instead of saving the tax system, his actions had undermined the IRS, breached the public trust, and violated the privacy of thousands of American taxpayers.”

Littlejohn and his attorneys declined to comment after the sentencing. They had argued that five years in prison would be “extreme.”

Reyes said that the House Committee on Ways and Means obtained six years of Trump’s tax returns through legal means, after winning a years-long court battle, and that Littlejohn’s actions risked damage to the U.S. taxation system by eroding the public’s expectation of privacy in their most sensitive financial information.

An attorney for Trump, Alina Habba, delivered a statement in court when Littlejohn pleaded guilty in October, urging the judge to impose a five-year prison term. Another victim, Sen. Rick Scott (R-Fla.), sat at the front row of the courtroom gallery for Littlejohn’s sentencing on Monday and complained during brief remarks before the judge that he had gotten “the plea deal of the century” by being charged with a single felony count.

Reyes on Monday also expressed astonishment that the Justice Department had pursued only one charge in Littlejohn’s case. “The fact that he did what he did, and he’s facing one felony count — I have no words for it,” Reyes told Jacobson. “Make it make a little bit more sense.”

Jacobson noted that Littlejohn chose to plead guilty relatively early in the investigation and that prosecutors probably would have filed more criminal charges had they taken the case to a grand jury for an indictment.

After being elected in 2016, Trump reneged on a promise to release his tax returns. In an editor’s note accompanying the first article based on Littlejohn’s disclosures, the Times’s then-executive editor, Dean Baquet, wrote: “Every president since the mid-1970s has made his tax information public. The tradition ensures that an official with the power to shake markets and change policy does not seek to benefit financially from his actions.” When Littlejohn pleaded guilty last year, a Times spokesman said, “We remain concerned when whistleblowers who provide information in the public interest are prosecuted.”

Federal prosecutors said in a court filing this month that ProPublica “has continued to publish stories using the data disclosed” by Littlejohn even after he pleaded guilty. The news organization’s reports lay out how many of the richest Americans, including Jeff Bezos, Bill Gates and Elon Musk, employ financial strategies to slash their federal tax bills. (Bezos owns The Post.)

Prosecutors said Littlejohn in 2017 sought to rejoin the firm he had been working for “with the hope and expectation of accessing and disclosing” Trump’s tax data, and “reorganized his entire life around this crime.”

Defense attorneys said Littlejohn excelled at his work, started an online poker analytics business while on a break from consulting and “will never again have access to tax records, or any other confidential government information.”