President Trump on Tuesday said that President Biden was not actually in charge of America when he held the White House, alleging that “radical left lunatics … were running our country.”

Speaking to reporters at the Capitol, Mr. Trump announced his intention to “look into” instances of autopen use following Mr. Biden’s recent disclosure of a prostate cancer diagnosis and the release of audiotapes that confirm Mr. Biden’s diminished cognitive acuity while in office. An autopen uses a robotic arm with a pen attached to add digitally recorded signatures onto paper, meaning the signer need not be present for — or even aware of — its use.

Earlier this year, the Heritage Foundation produced an analysis that showed that Mr. Biden’s executive actions toward the end of his term — including his pardons of his family members — had all been signed by autopen, with the exception of his letter stating his intention not to seek re-election.

The president’s vow to investigate comes as the House Oversight Committee has opened an investigation into whether Mr. Biden’s cognitive functions were sound enough to authorize aides to use an autopen tool to sign important documents on his behalf.

“Biden — look, It’s a very sad thing what happened, but we’re going to start looking into this whole thing with who signed this legislation. Who signed legislation opening our border? I don’t think he knew. I said, ‘There’s nobody that can want an open border. Nobody,’” Mr. Trump told reporters. “And now I find out that it wasn’t him. He autopenned it.”

“Who was operating the autopen? This is a very serious thing,” he said. “We had a president that didn’t sign anything. He autopenned almost anything. He opened the borders of the United States of America.”

The president also said Democrats actually wanted Senator Sanders, a Democratic socialist from Vermont, to be president, but then realized Mr. Biden may be a blessing. “After about two weeks, they said, ‘Wait a minute, this is a gift. He’ll do anything. We’re going to use the autopen,’ and they use the autopen and everything,” Mr. Trump said. “We are going to go into very much … remember what I said, the autopen, this government was illegally run for four years.”

Mr. Trump has previously raised concerns regarding Mr. Biden’s use of the autopen, particularly questioning the validity of pardons he issued for several top government officials and a slew of family members on his last day in office. 

While Mr. Trump did not specify which immigration policies he believed were signed with the autopen, he highlighted several contentious decisions from Mr. Biden’s presidency. These include the 2021 repeal of the Trump-era “metering” policy, which had limited the number of asylum seekers allowed at ports of entry, and the 2023 expiration of Title 42, a pandemic policy allowing for the quick expulsion of migrants.

A former United States attorney appointed to investigate Mr. Biden’s pardons, Ed Martin, announced on Sunday that a Department of Justice probe is officially under way. 

“The integrity of the American Pardon system requires that we examine the Biden pardons and who did what. We will get to the bottom of it. Count on us,” Mr. Martin, who serves as U.S. pardon attorney and weaponization tsar in the Department of Justice, wrote in a post on X.

Hours before Mr. Trump took the oath of office on January 20, the White House announced pardons for a former director of the National Institute of Allergy and Infectious Diseases, Anthony Fauci, and a former chairman of the Joint Chiefs of Staff, General Mark Milley. 

With less than 30 minutes left in his term, Mr. Biden pardoned members of his family, including his brother James B. Biden and his wife, Sara, sister Valerie Biden Owens, brother-in-law John T. Owens, and brother Francis W. Biden. The former president had pardoned his son, Hunter, for tax and gun crimes a month earlier.

The investigation into the 11th-hour pardons follows an announcement by Representative James Comer, chairman of the House Oversight Committee, that he is opening a House investigation. The Kentucky Republican charged that evidence suggests not only were pardons allegedly issued with minimal oversight during Mr. Biden’s final days and weeks in office, but several executive orders in his final months may have also been signed using an autopen.

“Joe Biden wasn’t capable of making decisions; he wasn’t coherent,” Mr. Comer said, suggesting White House staffers may have been responsible for key actions under the Biden administration during its concluding months. 

The confirmation that a DOJ  investigation is under way also comes after the release of audio recordings of Mr. Biden‘s interview with Special Counsel Robert Hur. The tapes, which were kept private by Attorney General Garland, show that during an October 2023 interview with Mr. Hur’s team, Mr. Biden was not entirely lucid, suffering memory lapses, including a failure to remember the year his oldest son died, as well as repeatedly stumbling over his words. 

In his final report after a probe into claims that Mr. Biden mishandled classified documents, Mr. Hur decided not to press charges, saying, “Mr. Biden would likely present himself to a jury, as he did during our interview of him, as a sympathetic, well-meaning, elderly man with a poor memory.”

Mr. Trump says the newly released tapes show a “bigger scandal” about the use of an autopen under the Biden White House. 

“Whoever had control of the ‘AUTOPEN’ is looking to be a bigger and bigger scandal by the moment,” Mr. Trump posted to Truth Social on Friday. In an earlier post on his social media platform, Mr. Trump wrote, “The ‘Pardons’ that Sleepy Joe Biden gave to the Unselect Committee of Political Thugs, and many others, are hereby declared VOID, VACANT, AND OF NO FURTHER FORCE OR EFFECT, because of the fact that they were done by Autopen.”