In 2018, Paul Atkins was paid $1,450 an hour to be an expert witness by Devon Archer’s lawyers as they tried to undermine accusations that their client defrauded a Native American tribal entity and others out of $60 million.
While Mr. Archer was convicted anyway, he was pardoned by President Trump in March.
And last week, with Mr. Atkins serving as the Trump-appointed chairman of the Securities and Exchange Commission, his agency moved to dismiss a civil case against Mr. Archer related to the same fraud.
Mr. Archer had earned fans in Mr. Trump’s circles by providing information about the dealings of his onetime business partner Hunter Biden, the son of former President Joseph R. Biden Jr., but the Bidens were not implicated in the fraud that was the subject of the S.E.C. enforcement action.
An S.E.C. spokesman said Mr. Atkins recused himself from the decision to drop the case. But the episode highlighted critics’ concerns about the deregulatory instincts and Wall Street connections of Mr. Atkins, who built a lucrative career advising some of the very financial interests he is now meant to oversee.
Since before Mr. Atkins’s confirmation hearing, Senator Elizabeth Warren, a Massachusetts Democrat, has pushed him for information about a consulting firm he owned called Patomak Global Partners and chided him for not being more forthcoming.
“Now we all know why,” Ms. Warren said in a statement to The New York Times on Tuesday. She accused Mr. Atkins of leading a “weaponization of the S.E.C. to serve his Wall Street friends at the expense of Main Street investors.”
In the years after Mr. Atkins left his position as an S.E.C. commissioner under President George W. Bush and founded Patomak in 2009, it became a go-to consultancy for major financial interests facing scrutiny in Washington or the courts.
During Mr. Atkins’s time at the helm, Patomak’s client roster included Bank of America, Barclays Bank, Deutsche Bank and Goldman Sachs, as well as an arm of the Singapore state-owned investment firm Temasek and the cryptocurrency company FalconX, among others, according to a disclosure he filed in February that covered the preceding two years or less.
During that time, Mr. Atkins earned nearly $3.7 million from his work at the firm, according to the disclosure. In July, Mr. Atkins filed paperwork indicating that he sold the firm — which this week listed more than 40 partners, employees, advisers and consultants on its website — for an amount between $25 million and $50 million.
He did not reveal the identity of the buyer, despite a request last month from Ms. Warren to do so.
The firm did not respond to a request for comment.
Before he was confirmed as S.E.C. chairman, Mr. Atkins had pledged to recuse himself unless he received a waiver for one year from any matters involving clients of the firm, or any of his other interests, which included cryptocurrency investments and positions.
Patomak helps clients develop compliance programs, prepare for government reviews and handle legal scrutiny, including by offering expert witness testimony in court proceedings.
For instance, Mr. Atkins advised the cryptocurrency exchange FTX before it collapsed in 2022 and became the target of investigations by the S.E.C. and the Justice Department.
And, in a civil class action lawsuit, Mr. Atkins testified in 2016 that a hedge fund firm then known as SAC Capital had “best practices” compliance provisions. That was despite the firm having pleaded guilty about two years earlier to criminal insider-trading violations and agreeing to pay a record $1.2 billion penalty.
Mr. Atkins’s work as an expert witness often put him at odds with the S.E.C., and sometimes led to questions about his integrity.
During Mr. Archer’s criminal trial, a federal prosecutor in Manhattan pointed to the civil case against SAC, noting, according to a transcript, that Mr. Atkins “concluded that SAC compliance programs were adequate during the time when they committed one of the largest securities frauds.”
Mr. Archer’s lawyer objected, accusing the prosecution of “trying to display or illustrate that this is someone who was hired by guilty people to concoct false defenses.”
Mr. Atkins characterized Patomak’s work differently, telling the court during the Archer trial that “we help if people get in trouble, if the government is going after them.”
In Mr. Archer’s case, that meant providing testimony that the defense used to try to buttress its argument that the client was not complicit in the securities fraud scheme.
Mr. Atkins estimated during the trial that he had spent between 20 and 30 hours on the case at a rate of $1,450 per hour, which would translate to between $29,000 and $43,500, before accounting for the hours of other Patomak staff members who also worked on the case.
While Mr. Archer was found guilty by a jury, the district court judge who was presiding over the case set aside the verdict and ordered a new trial, citing concerns “that Archer lacked the requisite intent and is thus innocent of the crimes charged in this indictment.”
An appeals court later reversed the district court judge, reinstating the jury verdict.
Mr. Trump’s pardon, combined with the S.E.C.’s decision to drop the civil case, could clear the way for Mr. Archer to become involved in securities-related business again.
He and his lawyer did not respond to requests for comment.
Sharon LaFraniere contributed reporting.