Originally Published: 15 MAY 23 15:58 ET

By Jack Forrest and Marshall Cohen, CNN

(CNN) -- John Durham, the special counsel who led the investigation into potential misconduct in the FBI's Trump-Russia probe, has made a career of investigating high-profile public corruption.

In a 300-plus page report, the Trump administration appointee determined that the FBI should never have launched its investigation into connections between Donald Trump's campaign and Russia during the 2016 election, according to the report compiled over three years and released on Monday.

Durham, 73, was appointed to serve as special counsel in October 2020 by then-Attorney General William Barr. He previously was the Justice Department's top prosecutor in Connecticut -- a position he was appointed to in 2017 and left in 2021.

He drew some bipartisan support in 2019 when he was directed by Barr to start reviewing whether intelligence and law enforcement violated the law in investigating the 2016 Trump presidential campaign, even as Democrats blasted Barr's probe as political.

Democratic Connecticut Sen. Chris Murphy told CNN at the time that Durham had "a reputation of being apolitical and serious," while Mark Meadows -- then the Republican chairman of the hardline Freedom Caucus -- called Durham an "outstanding choice."

Durham, who became a lawyer in 1975, is known for having handled high-profile, sensitive investigations in both Democratic and Republican administrations during his decadeslong career with the Justice Department.

He was appointed by then-Attorney General Janet Reno in 1999 to investigate corruption surrounding the use of FBI informants in Boston, and later by then-Attorney General Michael Mukasey to investigate the CIA's destruction of videotapes of detainee interrogations in 2008. Durham closed the latter probe without bringing any charges.

In addition to his work as a special prosecutor, Durham has extensive experience as a trial lawyer. He went after gangs in New Haven, prosecuted mob figures, and secured a guilty plea from former Connecticut Gov. John Rowland, a Republican who admitted to corruption.

Durham graduated from the University of Connecticut School of Law and received his undergraduate degree from Colgate University. He graduated with honors, according to his official biography.

His first job was with VISTA, now known as AmeriCorps, where he worked as a lawyer in Montana and provided legal services to the Crow Indian Tribe and its members. His work there largely focused on issues regarding land use and natural resources, he told lawmakers.

Durham later returned to Connecticut and became an assistant state's attorney. He joined the Justice Department in 1982, launching a nearly four-decade federal career.