Over a cup of tea in Rome on Friday, Kate Beckinsale was describing how her next film is about a young American girl jailed in a medieval Italian town for the murder of a British student, and she was insisting that it is not about Amanda Knox. "That case is peripheral," said the British actor, who is best known for her role as Selene, the gun-toting vampire in the Underworld series of films. "This is not a whodunnit."

But that is unlikely to stop headline writers linking Beckinsale with Knox, the Seattle-born student whose every court appearance in her trial for the murder of Meredith Kercher in 2007 was treated like a Hollywood red carpet moment, and whose guilt or innocence still provokes furious and sometimes fanatical debate in online forums as the case grinds through the Italian courts six years later.

Beckinsale, 40, said she was ready for the attention. "I've done three films dressed head to toe in latex, so don't think I haven't had my share of nutters."

Beckinsale was in Rome to research her role as a journalist in The Face of an Angel, also starring Daniel Bruhl and Cara Delevingne, which starts filming in the Italian capital and Siena next week and is directed by Michael Winterbottom. She will play a character based on American CNN reporter Barbie Latza Nadeau, one of the pack of journalists who followed the case, storming up and down the cobbled streets of Perugia, pushing lawyers for quotes and access to court documents and filing copy from the cramped press room at the medieval city court as the world divided into pro- and anti-Knox camps.

Winterbottom bought the rights to Latza Nadeau's book about the case – which has seen her pilloried for suggesting that Knox may be guilty – but decided to focus his film on the journalists themselves, before opting to frame the story around a film director arriving in Italy to buy the book rights to a murder case from an American journalist in an attempt to rebuild his wobbling career. In 2010, when he visited Perugia and attended a hearing in the murder trial, Winterbottom said his film would not focus on the pair. "I have no view on whether they did it. The film will not be about that," he said.

Winterbottom is no stranger to mixing fact and fiction. His breakthrough film in 1997, Welcome to Sarajevo, portrayed the real-life struggle of ITN correspondent Michael Nicolson to save orphans in the war-torn Balkans.

Beckinsale was being given a tour of the offices used by Latza Nadeau, who has also worked for the Daily Beast, at the foreign press association round the corner from the Trevi fountain. Latza Nadeau, a 47-year-old mother of two, said she was still coming to terms with being portrayed by one of Hollywood's most glamorous women.

Beckinsale was wondering if her insurance would let her career around on a moped, as Latza Nadeau does. "I know it doesn't allow me to windsurf," she said, adding that while the film requires her to drive a car, she has no licence. "If I drove in Rome, I would kill myself and others," she said. "My parents have a house in Umbria and it took my mother seven years to get up the courage to drive from the airport."

The actor was careful to reserve judgment on whether she thought Knox, with her then boyfriend, Raffaele Sollecito, fatally stabbed Kercher in her student digs in Perugia, a crime for which they were jailed, then acquitted on appeal, only to be sent back to trial this year by Italy's supreme court. "I have read lots of books, watched a lot of YouTube," she said. "I had an opinion before I started researching, but then it became opaque."

The film marks Beckinsale's return to an Italian set after she appeared in Kenneth Branagh's Much Ado About Nothing in 1993, which she filmed in Tuscany during a summer holiday from Oxford University.

After questioning Latza Nadeau about Italy's snail-paced legal system, which means Knox and Sollecito could still be on trial by the time the film is finished, Beckinsale said she was relishing her role. "Playing a bright woman is a relief. There aren't so many [of those roles] flying around."

But she said she was still trying to fathom the appeal of the one character who will not be appearing in the film: Amanda Knox. "Is the bottom line that she is not what a murderer looks like?"