It had to do with a young black man who had been kidnapped and brutally murdered by two members of the Ku Klux Klan.
The Klansmen, Henry Hayes and Tiger Knowles, slit the victim's throat and hung his body from a tree.
They carried out the attack in retribution for a jury acquitting a black man in the slaying of a white police officer.
As Sessions learned that some members of the Klan had smoked marijuana on the evening of the slaying, he said aloud that he thought the KKK was: "OK until I found out they smoked pot."
Sessions insists he was joking. But the damage was done.
The comment, and others like it, cost him a federal judgeship in 1986 and have been repeated time and again in summary form in newspaper and magazine articles over the years. They are often cited absent the full context in which they were made.
The issue has reemerged and could have magnified importance with President-elect Donald Trump's nomination of Sessions to become US attorney general.
But a CNN examination of the statements
at issue in that hearing three decades ago -- a defining moment in Sessions' life — reveals a more nuanced portrait than has sometimes been conveyed over the years.
A former colleague who testified in the hearing said he found it ironic that Sessions was being painted as racist for comments that came out while he was literally helping to take on the Klan.
"The way he was portrayed," retired Department of Justice prosecutor Barry Kowalski said, "was very unfair."
Jefferson Beauregard Sessions III was born in Alabama in 1946. He was a child of the segregated South and came of age during the Civil Rights Movement. He went to college in his home state and attended law school there as well.
Sessions worked briefly in private practice before signing on with the US Attorney's office in 1975. Six years later, he was appointed US attorney for the Southern District of Alabama by President Ronald Reagan.
In 1986, Reagan nominated him to become a federal judge, a lifetime appointment requiring confirmation by the US Senate. It was during a hearing before the Senate Judiciary Committee that Sessions' comments about the KKK became an issue.
Thomas Figures, an assistant US Attorney who worked under Sessions in Mobile, testified that he was present when Sessions made the remark and said he did not regard it as a joke.
Figures, who was African-American and passed away last year, also told committee members that Sessions had called him "boy" on several occasions and once cautioned him to "be careful what you say to white folks" after Figures had spoken harshly to a secretary who was white.
Another federal prosecutor, J. Gerald Hebert, testified that Sessions had called the ACLU and NAACP "un-American" and "communist-inspired." According to Hebert, Sessions said the two groups "forced civil rights down the throats of people."
Hebert, a veteran civil rights prosecutor, told the committee he had "very mixed feelings" about testifying about the conversations that he said had taken place over a matter of years. He said he and Sessions would engage in "spirited debate" about civil rights and that he sometimes wondered if Sessions was baiting him with controversial statements. Sessions, he said, "has a tendency sometimes to just say something, and I believe these comments were along that vein."
Asked by a committee member whether he considered Sessions a racist, Hebert responded: "No, I do not."
The same committee member, Sen. Jeremiah Denton, an Alabama Republican, asked Hebert: "If Mr. Sessions says he would be fair as a judge, would you believe him?"
"He is a man of his word," Hebert responded, "and when he says something, I believe him."
Some witnesses at the hearing came to Sessions defense on issues of race, including Larry Thompson, an African-American former US Attorney in neighboring Georgia.
Thompson testified that he had known Sessions as a colleague and friend for years and had twice shared a hotel room with him on work trips to cut costs.
He told the committee he considered Sessions "a good and honest man untainted by any form of prejudice."
Kowalski, a prosecutor in the Justice Department's civil right division in Washington, also heard Sessions make the statement about thinking the Ku Klux Klan was OK until learning that some of its members smoked marijuana.
Kowalski testified that he considered the comment a joke.
In a recent interview with CNN, Kowalski said Sessions played a pivotal role in getting the case against the Klansmen off the ground.
Kowalski said the slaying of the young black man, Michael Donald, was initially seen by local authorities as the result of a drug deal gone bad, even though his body was found hanging in a tree across the street from a member of the Klan's residence.
Kowalski said Sessions was supportive of his idea to convene a grand jury to investigate whether the killing was racially motivated and therefore qualified as a federal civil rights crime.
"At a time when many US Attorneys in the South were not always welcoming to the Civil Rights Division, Jeff Sessions was," said Kowalski, 72, and now retired from the Justice Department. "Jeff had the vision and the courage and the desire to do right."
Kowalski, who went on to prosecute the Los Angeles police officers who beat black motorist Rodney King in 1991, described himself as a liberal Democrat who disagreed with most of Sessions' political views.
But he said he witnessed no evidence that Sessions was a racist, either in how he spoke or how he treated people.
Kowalski said he could not directly contradict Figures. But he said he has struggled to comprehend how Figures took the comment about the Klan seriously.
"I have trouble understanding how he came to that conclusion," he said.
Kowalski said the allegation that Sessions called Figures "boy" or admonished him for the way he spoke to white people was "inconsistent with the way he behaved when I was around."
Testifying on his own behalf at the hearing, Sessions acknowledged that he was "loose with my tongue on occasion" and may have made comments about the ACLU and NAACP that could have been misconstrued "but I really did not mean any harm by it."
He denounced the KKK as a "force for hatred and bigotry" and said he was shocked that Figures or anyone else would suggest he thought otherwise.
"I am not the Jeff Sessions my detractors have tried to create," Session told the committee. "I am not a racist."
Leading the charge against Sessions at the time was the late Democratic Sen. Edward Kennedy of Massachusetts. He called Sessions "a throwback to a shameful era that I know both black and white Americans thought was in our past" and "a disgrace to the Justice Department."
The committee voted 10-8 against advancing Sessions' nomination to a hearing before the full Senate.
Sessions was elected attorney general of Alabama in 1994. Two years later, he was elected to the US Senate, where he is now serving his fourth term.
In the Senate, he has earned the reputation as one of the institution's most conservative Republicans, taking reliably right of center stances on social and economic issues alike. He is particularly passionate on issues of immigration. In 2007, he was a key player in the successful effort to defeat President George W. Bush's proposed overhaul of national immigration policy, which would have granted legal status to millions of undocumented immigrants.
Sen. Lindsey Graham, a Republican from South Carolina, said he's known Sessions as a friend and colleague for two decades and has never seen an indication that he's "motivated by race or religion."
"He's just a very conservative guy," Graham said. "He's very sincere and passionate about his beliefs."
Sessions' positions on civil rights issues have not won him any fans at the NAACP. He's received consistent "Fs" on the group's legislative report cards for the past decade and a half.
Cornell William Brooks, the group's president, blasted Sessions' nomination, citing what he called a "very disturbing and recurring theme of hostility to and toward civil rights" exhibited over his career.
He said Sessions nomination along with a top post being awarded to Stephen Bannon were deeply troubling from a civil rights perspective.
"The campaign has been blowing a racist dog whistle," Brooks said. "Now the campaign rhetoric is becoming transition reality."
Hebert, the Justice Department prosecutor who testified about Sessions alleged comments about the NAACP and ACLU, said he has had no contact with his former colleague since the hearing three decades ago.
But he has followed Sessions' career through his public comments and votes in the Senate. He said he noticed "a pattern" of behavior that has concerned him, including voting against the nomination of several high profile appointees who were non-white.
All things considered, Hebert, said, he found it a frightening prospect that Sessions would be appointed attorney general.
"It's a collection of things from over the years. I think it's frightening for people who believe in fairness and equality for him to be running the Justice Department."
Sessions was the first US senator to endorse Trump for president, which he did in February.
Sessions' past -- or the version that emerged from the Judiciary hearing -- was quick to follow.
"Alabama Senator Jeff Sessions had a lengthy history of making racist statements," a headline in The Nation charged at the time.
The racial allegations made news again when Trump questioned the impartiality of federal judge Gonzalo Curiel based on his Mexican heritage and Sessions declined comment on the matter.
"'Racist' Senator Sticks With Donald Trump," a Daily Beast headline proclaimed
The negative coverage of Sessions appears to have had little impact on Trump, which is not surprising given his oft-stated distrust and disdain for the media.
"The President-elect has been unbelievably impressed with Senator Sessions and his phenomenal record as Alabama's Attorney General and US Attorney," read a statement following a meeting at Trump Tower. "It is no wonder the people of Alabama re-elected him without opposition."