Kenneth Starr, who has died aged 76 after complications from surgery, was the independent prosecutor whose investigation of Bill and Hillary Clinton’s investment in a real-estate project called Whitewater began in somewhat pious partisanship and descended into prurience. It led to President Clinton’s impeachment for perjury based on his lying about his relationship with a White House aide, Monica Lewinsky.

The Clinton impeachment was an American watershed. Following the OJ Simpson trial of the mid-1990s, it established scandal as the fuel that powered television news, but more importantly it pointed the way to use congressional investigation in order to disrupt a presidency, a tactic followed repeatedly against the Barack Obama administration, including six House investigations, lasting more than two years, of the secretary of state, Hillary Clinton, over the assault on the US embassy in Benghazi, Libya.

His proteges, including the supreme court chief justice, John Roberts, and justice Brett Kavanaugh, Starr’s key Whitewater aide, spoke highly of him following his death. His career was inexorably bound to sex scandals, starting with his 1993 review of the Republican Senator Bob Packwood’s diaries in Senate ethics committee hearings over accusations of sexual abuse and assault.

As part of Jeffrey Epstein’s legal team, Starr crucially lobbied federal authorities to drop their sex-trafficking prosecution and allow Epstein to plead guilty, in 2008, to lesser state charges with a far lighter sentence in Florida.

Towards the end of his career, in 2016, Starr was forced to step down as president of Baylor University over that institution’s failure to pursue rape charges against football players.

And while supporters rejected accusations of partisan hypocrisy, the man whose Whitewater mantra was “there’s no excuse for perjury – never, never, never. There is truth and the truth demands respect,” wound up defending the then president Donald Trump during his first impeachment trial, in 2020, having already, as an analyst on Fox News, advised that Trump’s impeachment would be “bad for the country”.

Starr’s Washington career had its roots in his religious upbringing. Born in Vernon, Texas, he grew up in small towns in the state’s panhandle where his father, Willie D Starr, was a barber and sometime minister in the Churches of Christ; his mother, Vannie (nee Trimble), was a homemaker. They moved to San Antonio, where Kenneth was voted “most likely to succeed” in his high school.

Following two years at what is now Harding University in Arkansas, he transferred to George Washington University in DC, graduating in 1968 with a BA in history. In 1970 he took a master’s in political science at Brown University, Rhode Island, and married Alice Mendell, who worked in public relations, before getting his law degree from Duke University, North Carolina, in 1973.

After working as a clerk for the supreme court chief justice Warren Burger, in 1977 Starr joined the law firm Gibson Dunn. He went on in 1981 to become chief of staff to William French Smith, Ronald Reagan’s attorney general; two years later Reagan appointed Starr to the US court of appeals for the district of Columbia.

In 1989 Starr left the bench to become George HW Bush’s solicitor general; Roberts was his assistant. The following year Bush considered Starr for a place on the supreme court, but Republicans in Congress feared Starr was not conservative enough. Ironically, Bush’s appointee, David Souter, turned out to be far less conservative than they had hoped. Two years later, Starr’s review of Packwood’s diaries convinced the ethics committee chair, Mitch McConnell, of Starr’s deft conservativism.

So, when the original Whitewater independent counsel, Robert B Fiske, issued his interim report clearing the Clintons of fraud and of any involvement in the suicide of the White House lawyer Vince Foster, Fiske was ousted and, in August 1994, Starr appointed.

By 1997, despite plea bargains and imprisoning witnesses who refused to implicate the Clintons, Starr had done little but endorse Fiske’s findings about Foster. He wanted to leave and become dean of public policy at Pepperdine College, but was convinced to stay until the 1998 elections.

In January 1998, Clinton gave a deposition in a civil suit for sexual harassment filed by Paula Jones, saying he had never had a workplace affair; one of the women included in his denial was a White House staffer named Monica Lewinsky.

Two days later, Starr, who had advised Jones’s lawyers, was given tapes made secretly of Lewinsky admitting her affair with Clinton. This led to the orgy of coverage about semen-stained dresses and inserted cigars, as Lewinsky’s grand jury testimony set up a perjury trap for Clinton sprung by Kavanaugh, who aimed “to make his pattern of revolting behaviour clear, piece by painful piece”.

As the case grew steamier, Kenneth Starr was rebranded “Ken” in the media, in an effort to make his shock more like an average Joe’s. Clinton was forced to answer a series of graphically explicit questions about the details of his relationship with Lewinsky. The House duly impeached, but the Senate acquitted Clinton.

Starr rejoined the corporate law firm Kirkwood and Ellis, best known for defending the tobacco group Brown & Williamson.

In 2004 he finally went to Pepperdine, as dean of the law school. In later cases he argued for Blackwater mercenaries accused of murdering civilians in Iraq, claiming they had “constitutional immunity”, and against California’s legalisation of gay marriage.

He became president of Baylor, in Waco, Texas, in 2010, and chancellor in 2013. Although at least 17 women had accused football players of rape since he became president, he claimed during an investigation that “never was it brought to my attention there were issues”.

He was found to have mishandled the accusations of sexual assault against members of the football team and removed as president in 2016; he then resigned as chancellor and as a professor of law.

In his 2018 memoir, Contempt, Starr wrote: “I deeply regret that I took on the Lewinsky phase of the investigation, but there was no practical alternative.”

He is survived by Alice, their son, Randall, and two daughters, Carolyn and Cynthia, and by a sister, Billie Jeayne, and a brother, Jerry.