The House Oversight Committee heard testimony this week from a key Biden official as part of its investigation into the former president’s health decline and issued a subpoena to former first lady Jill Biden’s top aide after he refused to appear voluntarily.

Biden left office in January, but questions about his mental acuity and decline while in office continue to mount after the release of audio of his interview with former special counsel Robert Hur and his cancer diagnosis, drawing attention to a number of actions taken in his final days in office and beyond. 

Here's a look at the known, active investigations into the former president and his team: 

HOUSE GOP SECURES FOUR KEY WITNESSES IN BIDEN MENTAL-DECLINE PROBE AS FORMER AIDES AGREE TO TALK

House Oversight investigation into alleged cover-up of Biden’s mental decline

The House Oversight Committee, led by Chairman James Comer, R-Ky., is leading an investigation into an alleged cover-up of Biden’s mental decline. 

The investigation is looking into whether those inside Biden’s inner circle knowingly colluded to hide the former president’s declining mental acuity and used methods to circumvent the former president when it came to the issuance of important orders, particularly through the use of an autopen tool used to mimic the president’s signature. 

Some Biden aides agreed to voluntarily testify for transcribed interviews, including the director of Biden's former Domestic Policy Council, Neera Tanden; Biden's assistant and senior advisor to the first lady, Anthony Bernal; former special assistant to Biden and Deputy Director of Oval Office Operations, Ashley Williams; and Annie Tomasini, Biden's deputy chief of staff.

Tanden appeared before the House Oversight Committee Tuesday. She told lawmakers she had "minimal interaction with Biden despite wielding tremendous authority," Comer said. 

"She explained that to obtain approval for autopen signatures, she would send decision memos to members of the president's inner circle and had no visibility of what occurred between sending the memo and receiving it back with approval," Comer explained. "Her testimony raises serious questions about who was really calling the shots in the Biden White House amid the president's obvious decline." 

Bernal had confirmed his appearance for a voluntary transcribed interview June 26. But after the White House counsel’s office informed him it was waiving executive privilege for the Oversight Committee’s investigation, he refused to appear. 

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Comer has now subpoenaed Bernal to compel his testimony. 

"Given your close connection with both former President Biden and former first lady Jill Biden, the Committee sought to understand if you contributed to an effort to hide former President Biden’s fitness to serve from the American people," Comer wrote in a letter to Bernal Thursday with the subpoena attached. 

"You have refused the Committee’s request. However, to advance the Committee’s oversight and legislative responsibilities and interests, your testimony is critical." 

Comer said the committee "seeks information about your assessment of and relationship with former President Biden to explore whether the time has come for Congress to revisit potential legislation to address the oversight of presidents’ fitness to serve pursuant to its authority under Section 4 of the Twenty-Fifth Amendment or to propose changes to the Twenty-Fifth Amendment itself." 

Williams will testify July 11, and Tomasini will testify July 18. 

Biden’s former White House doctor, Kevin O’Connor, declined an invitation to sit for a transcribed interview scheduled for June 27. 

Comer subpoenaed O’Connor to compel that testimony. 

Comer sent letters to five more top former Biden staffers, putting his total outreach in the investigation to 10 people so far.

The latest round of letters are being sent to former White House chief of staff Ron Klain, former senior communications advisor Anita Dunn, former top advisors Michael Donilon and Steve Ricchetti and former deputy chief of staff for policy Bruce Reed.

SCOOP: GOP PUSH FOR NEW HOUSE COMMITTEE TO PROBE BIDEN DECLINE 'COVER-UP' GAINS STEAM

Senate Judiciary Committee

The Senate Judiciary Committee held a hearing Wednesday morning, "Unfit to Serve: How the Biden Cover-up Endangered America and Undermined the Constitution." 

The hearing included testimony from three experts, including University of Virginia law professor John Harrison, Heritage Foundation fellow Theodore Wold and a former White House press secretary from the first Trump administration, Sean Spicer. 

The conservative Heritage Foundation's Oversight Project first investigated the Biden administration's use of an autopen earlier in 2025 and found that the same signature was on a bevvy of executive orders and other official documents, while Biden’s signature on the document announcing his departure from the 2024 race varied from the apparent machine-produced signature.

Wold testified before the committee and described the alleged cover-up of Biden's declining health a "constitutional crisis."

Republican senators blasted their Democratic colleagues for boycotting and walking out of the hearing. 

"I will note that few of my Democratic colleagues are here today," Republican Texas Sen. John Cornyn said Wednesday. "Thank you to Sen. Welch from Vermont for being here, leaving us with no other option than to take the boycott of this hearing as an admission of guilt for their role in this crisis.

"We must not turn away from the search for answers, and it is not an overstatement to say that the future of our country could one day hinge on how we choose to act or not act on this very issue."

Vermont Democratic Sen. Peter Welch and Illinois Democratic Sen. Dick Durbin did attend the start of the hearing, with Durbin abruptly walking out after describing the hearing as a distraction and accusing Republican colleagues of being "asleep at the wheel" with other legal issues within the Trump administration due to their focus on Biden. 

BIDEN STRUGGLES WITH WORDS, KEY MEMORIES IN LEAKED AUDIO FROM SPECIAL COUNSEL HUR INTERVIEW

"In the last week alone, several events have demanded this committee's immediate attention," Durbin said Wednesday. "The horrific assassination in Minnesota, the treatment of our colleague Sen. Padilla by federal agents in Los Angeles and President Trump's unprecedented deployment of the U.S. military in Los Angeles.

"We should hear without delay from Attorney General Bondi and FBI Director Patel about what they are doing to address the unacceptable political violence in our country, including threats to Article III judges and justices, as well as members of Congress," Durbin added. "And we need to hear from the Homeland Security Secretary Noem about the treatment of our colleague, Sen. Padilla, and this administration's mass deportation campaign against immigrants." 

Welch also left the hearing after declaring it would not benefit his constituents. 

Justice Department investigation into Biden pardons 

Biden used his final weeks as commander in chief to grant clemency and pardon more than 1,500 people in what the White House described at the time as the largest single-day act of clemency by a U.S. president.

The Justice Department is reviewing the list of people granted pardons by Biden amid concerns about his use of an autopen to automatically sign documents. 

DOJ Pardon Attorney Ed Martin is reviewing the list of Biden-era pardons granted during the former president’s final weeks in office, including the one granted to his son, Hunter, and the preemptive pardons granted to Dr. Anthony Fauci, former Gen. Mark Milley, Biden family members and members of the House Committee investigating the Jan. 6, 2021 riots. 

BIDEN ONLY HAND-SIGNED ONE PARDON DURING FINAL SPREE, AND IT WAS HIS MOST CONTROVERSIAL ONE

But Biden only signed one pardon by hand during his final weeks in office, and it was his most controversial, for his son, Hunter. 

Biden pardoned his son Hunter in December 2024 after vowing to the American people for months he would not do so. 

Hunter Biden was found guilty of three felony gun offenses during special counsel David Weiss’ investigation. The first son was also charged with federal tax crimes over his alleged failure to pay at least $1.4 million in taxes. 

Before his trial, Hunter Biden entered a surprise guilty plea. 

In December 2024, the former president announced a blanket pardon that applies to any offenses against the U.S. that Hunter Biden "has committed or may have committed" from Jan. 1, 2014, to Dec. 1, 2024.

"From the day I took office, I said I would not interfere with the Justice Department’s decision-making, and I kept my word even as I have watched my son being selectively, and unfairly, prosecuted," the former president said. 

HERE ARE BIDEN'S MOST CONTROVERSIAL PARDONS, MAINLY SIGNED USING AUTOPEN

"There has been an effort to break Hunter — who has been five and a half years sober, even in the face of unrelenting attacks and selective prosecution. In trying to break Hunter, they’ve tried to break me — and there’s no reason to believe it will stop here. Enough is enough," he said. 

"I hope Americans will understand why a father and a president would come to this decision." 

House Oversight investigation into alleged cover-up of Biden’s cancer diagnosis

Biden was diagnosed with an "aggressive form" of prostate cancer in May. 

"Last week, President Joe Biden was seen for a new finding of a prostate nodule after experiencing increasing urinary symptoms," Biden's team shared in a statement. "On Friday, he was diagnosed with prostate cancer, characterized by a Gleason score of 9 (Grade Group 5) with metastasis to the bone.

"While this represents a more aggressive form of the disease, the cancer appears to be hormone-sensitive, which allows for effective management. The President and his family are reviewing treatment options with his physicians."

JOE BIDEN DIAGNOSED WITH 'AGGRESSIVE FORM' OF PROSTATE CANCER WITH METASTASIS TO THE BONE

During his presidency, Biden had a cancerous skin lesion removed from his chest, the White House said at the time. 

Biden, during a 2022 speech discussing pollution in his home state, said, "That’s why I and so damn many other people I grew up (with) have cancer."

But Comer has expanded his investigation into Biden’s mental decline to include an investigation into the timeline of when Biden learned he had cancer. 

BIDEN'S WHITE HOUSE PHYSICIAN SUBPOENAED AS REPUBLICANS DIG DEEPER INTO ALLEGED COGNITIVE DECLINE COVER-UP

"If you'll remember, Joe Biden did an interview several years ago and said he had cancer. The White House quickly issued a statement saying, ‘Oh, he misspoke,’" Comer said during an appearance on Fox Business’ "Mornings with Maria." 

"Now, how many people do you know in the history of the world that have misspoke saying they had cancer when they really didn't?

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"So, there's evidence out there that would suggest that there's been a cover-up with respect to his cancer for many years, just based on Joe Biden's own words."