Weiss, who was appointed to his post by Republican then-President Donald Trump, agreed to stay on the job into the Biden administration to complete a long-running probe into Hunter Biden's finances.
Hunter Biden, 53, agreed to plead guilty to two misdemeanor charges of willfully failing to pay income taxes and reached an agreement on a gun-related offense that could allow him to avoid a conviction, according to court filings.
Weiss, who was described by former colleagues as an independent-minded career prosecutor, was tasked with spearheading a highly sensitive investigation into the Democratic president's son, who has come under intense scrutiny from Republican lawmakers.
"I don't think he's thinking about the politics at all," said Thomas Ostrander, who worked with Weiss at law firm Duane Morris. "He's simply thinking about doing his job and doing what's appropriate under the circumstances."
Congressional Republicans criticized the plea deal on Tuesday. Representative James Comer, who is leading investigations into Hunter Biden on the House of Representatives Oversight Committee, called it a "slap on the wrist."
U.S. Attorney General Merrick Garland has previously vowed not to interfere in the criminal investigation and answered Republican criticism by emphasizing Weiss' role leading the probe.
Weiss was nominated to be U.S. attorney in Delaware by Trump in 2018 with the support of Delaware's two Democratic U.S. senators. He previously served as the top deputy in the office and was interim U.S. attorney during the early years of the 2009-2017 Obama administration.
Lawmakers credited Weiss with prosecuting corruption, money laundering, drug offenses and helping secure federal funding to combat illegal drug trafficking in Delaware.
Weiss, as the top U.S. prosecutor in the Biden family's home state, supervised the investigation from its start in 2018, focusing initially on potential violations of tax and money laundering laws in Hunter Biden's foreign business dealings, particularly in China, Reuters has reported.
The probe was not the first time Weiss worked on issues that sparked political intrigue. As a lawyer in private practice, Weiss' firm represented the family of Anne Marie Fahey, a secretary of Delaware's then-governor who went missing in 1996.
Weiss pressed federal authorities to get involved in the investigation, Ostrander said, a move that helped lead to the murder conviction of Delaware's former deputy attorney general.
Weiss also oversaw the prosecution of Christopher Tigani, a beer distributor who solicited donations for Joe Biden's unsuccessful 2008 presidential campaign and was later convicted of campaign finance violations, Politico reported.
Weiss' office suffered a setback in a high-profile corporate case in 2021 when a federal appeals court overturned the convictions of four former Wilmington Trust executives accused of hiding troubled loans in the aftermath of the 2008 financial crisis.
Prosecutors later agreed to drop all charges.
(Reporting by Andrew Goudsward; Editing by David Bario and Jonathan Oatis)
By Andrew Goudsward
