Amanda Knox, an American who was convicted and then exonerated of murdering her housemate while they were studying in Italy, on Wednesday lost another trial in an Italian court against slander charges related to the 2007 killing.

Ms. Knox was convicted by a court in Florence on charges that she had slandered a man who ran a bar where she worked by unjustly accusing him of killing her housemate, the 21-year-old Meredith Kercher, in 2007. Ms. Knox was sentenced by the court to three years in prison, time she has already served.

Ms. Knox was initially found guilty of slandering the man, Diya Lumumba, also known as Patrick, in 2009, a conviction that was upheld by various Italian courts. At the time of the killing, Mr. Lumumba ran a bar called Le Chic where Ms. Knox worked part time.

Ms. Knox declined to speak to reporters after the ruling on Wednesday. Standing at the front of the courtroom, she appeared distressed and held her husband, Christopher Robinson, in a long embrace.

“Amanda is very upset,” one of her lawyers, Carlo Dalla Vedova, said after the verdict was issued. He said that she had been looking forward to the trial as a way of putting an end to “17 years of judicial procedure.”

Her defense team said it would read the court’s full written ruling, which is expected within 60 days, and would then most likely appeal to Italy’s highest court.

Speaking to a courtroom packed with journalists earlier Wednesday, Ms. Knox, referring to her comments about Mr. Lumumba in 2007, described “the worst night of my life,” and said that she had been bullied by the police into accusing an innocent man of murder.

She told the court, speaking in Italian and with her voice cracking at times, that she had been a frightened 20-year-old who had been tricked and was “psychologically destabilized.” She said she couldn’t understand why the police, “who I had been raised to trust and obey,” were pressuring her to admit to something that was not true and to sign a document that was little more than “a mix of incoherent memories.”

The hearing on Wednesday is the latest turn in a legal journey whose echoes continue to reverberate nearly 17 years after the murder of Ms. Kercher, a British student, elicited headlines around the world and turned Ms. Knox into a tabloid staple.

A European court ruling and a change in Italian law allowed a new appeal by Ms. Knox over the slander charges, and Italy’s highest court in October ordered a retrial, which began in April.

Ms. Knox became a household name in 2007 when she was arrested with her boyfriend at the time, Raffaele Sollecito, then 23, for the murder of Ms. Kercher during what prosecutors described as a sex game gone wrong. All three were studying in the picturesque central Italian city of Perugia.

Ms. Knox was convicted in 2009 of the killing by an Italian court but acquitted on appeal. She returned to the United States in 2011 while her case bounced between various courts until she and Mr. Sollecito were exonerated by Italy’s highest court in 2015.

Ms. Knox, arriving early at the courthouse on Wednesday, had to navigate a crowd of camera operators waiting for her to appear. One of her lawyers said that she had been inadvertently struck in the forehead by a camera.

Speaking to the court, recalling the events that led her to accuse Mr. Lumumba, Ms. Knox said that Ms. Kercher had been the “victim of horrible violence.” In the days after Ms. Kercher’s death, Ms. Knox said that she had been “under shock and exhausted” and had never felt “so vulnerable in my life.”

It was at that point, she said, during a nightlong interrogation, that the police pressured her into naming Mr. Lumumba, with whom she had exchanged some text messages that night. She said one officer had slapped her.

In a handwritten statement the morning after the interrogation, she recanted her statements and wrote of her confusion: “I want to make clear that I’m very doubtful of the verity of my statements because they were made under the pressures of stress, shock and extreme exhaustion.”

Mr. Lumumba, who now lives in Krakow, Poland, did not attend Wednesday’s hearing and has not responded to requests for comment.

Since returning to the United States, Ms. Knox, now 36 and a mother of two, has become an advocate for people incarcercerated for crimes they did not commit and a campaigner for criminal justice reform.

Rudy Guede, a Perugia resident with a police history of break-ins, was tried separately and convicted in the murder case. He served 13 years of a 16-year-sentence and was released in 2021, recently making headlines after a former girlfriend accused him of physically abusing her. His lawyer said this week that the case involving the former girlfriend was still being investigated.

Although Ms. Knox recanted her statements accusing Mr. Lumumba, he was arrested, held in prison for two weeks and released only after one of his clients provided an alibi.

Mr. Lumumba sued for slander, and Ms. Knox was found guilty and sentenced to three years, which she served during her four years in prison.

In a December 2023 episode of “Labyrinths,” the podcast she hosts with her husband, Ms. Knox said the slander conviction still disturbed her.

For some, she said, it was “proof that I am a liar and I am an unsavory person and that I have something to hide and I’ve never told the full truth about what happened to Meredith and only somebody who was involved in the crime would ever even make statements that implicated themselves and others.”

There are no recordings of the interrogations that night, and Italian police officers sued Ms. Knox for slander for her depiction of the interrogation. She was tried and acquitted on those charges in 2016.

In 2019, Europe’s top human rights court ruled that Ms. Knox had been deprived of adequate legal assistance while being interrogated, violating her right to a fair trial, and ordered Italy to pay her 18,400 euros, or about $21,000 at the time, in damages, costs and expenses. The court also raised questions about the role of Ms. Knox’s interpreter, and said that Ms. Knox’s statements during the interrogation “had been taken in an atmosphere of intense psychological pressure.”

At the April hearing related to the slander case, the Italian prosecutor and Carlo Pacelli, Mr. Lumumba’s lawyer, argued that Ms. Knox had knowingly accused the bar manager to deflect attention from herself and derail the investigation.

Ms. Knox had been ordered to pay damages to Mr. Lumumba, but Mr. Pacelli said she had never given any money to his client. Because of the accusation, Mr. Lumumba lost his business, and he left Italy with his family.

“I am very sorry I was not strong enough to resist the pressure of the police and that he suffered for it,” Ms. Knox said on Wednesday before the ruling.

Another of Ms. Knox’s lawyers, Luca Lupária Donati, called the verdict on Wednesday “a serious judicial error,” adding, “We won’t stop here.”