The audacious murder of Italian fashion designer Gianni Versace, shot in cold blood on the marble steps of his Miami Beach villa in 1997, has never been a “whodunnit”. The perpetrator is well known.

He was 27-year-old Andrew Cunanan, a serial killer who had already murdered four men before gunning down Versace on a sticky July day over two decades ago. Cunanan killed himself in a houseboat over a week later, following what remains one of the biggest manhunts in US history.

But mystery still shrouds the murder, with numerous conspiracy theories as to why Cunanan targeted Versace and whether the two had been lovers.

The second season of American Crime Story, entitled The Assassination of Gianni Versace, seeks to filter these murky waters, relying heavily on Vanity Fair writer Maureen Orth’s bestselling book on the Versace murder, Vulgar Favours.

The series, starring Édgar Ramírez as Versace, Ricky Martin as his long-term lover Antonio D’Amico, Penélope Cruz as Gianni’s sister Donatella and Glee star Darren Criss as Cunanan, was filmed in Versace’s Miami Beach villa, now a boutique hotel, which looks much as it did when the designer lived there.

The series has received positive reviews from critics and viewers since it premiered in January in the US, with the exception of one family. The Versaces have broken years of silence to publicly condemn everything about the series and Orth’s version of events.

“The Versace family has neither authorised nor had any involvement whatsoever in the TV series about the death of Mr Gianni Versace,” reads a statement released by the fashion house.

“Since Versace did not authorise the book on which it is partly based, nor has it taken part in the writing of the screenplay, this TV series should only be considered as a work of fiction.”

Putting aside the family statement for a moment, it must be said that Orth is no slouch. She started following Cunanan after his second murder, analysing the gay scene in California where he had built a life on dreams and lies at a time when most of the mainstream media were nervous about broaching such topics.

She followed his trail from San Diego to San Francisco and on to Minneapolis and Chicago, and was ready to publish a piece in Vanity Fair on the unknown serial killer when she got the news that Versace might have been her subject’s fifth victim.

The story of a serial killer quickly became solely one about the murder of one of fashion’s greatest icons. “Versace’s killing meant calling the piece back, taking it apart on an impossible deadline and trying to stay ahead of what rapidly became the number one story in the country,” Orth wrote recently. 

“The media circus was on; in this pre-social-media time, Cunanan’s murder spree was an early harbinger of someone willing to do anything to become famous.”

Orth had Versace’s name in her notebooks long before Cunanan ever arrived in Florida. She was then the only one on the scene with insider knowledge of the suspect during the manhunt, from interviewing countless of Cunanan’s friends and associates.

Many told her conflicting tales based on Cunanan’s tangled web of lies, but they almost all agreed on one thing: Cunanan had met Versace.

American Crime Story picks up this thread and runs with it, which was always the Versace family’s greatest fear. They not only strongly deny that Versace knew Cunanan, they also denounce rumors that the fashion designer was HIV positive.

The Versaces were able to seal Gianni’s autopsy report and keep it from the press, so no one outside the family knows whether the designer had HIV, a cornerstone of Orth’s version of events.

As the theory goes, Cunanan was worried he had had HIV and suspected Versace was the one who gave it to him. But as the Versace family makes clear in its statement, that version is conjecture: “Orth makes assertions about Gianni Versace’s medical condition based on a person who claims he reviewed a postmortem test result, but she admits it would have been illegal for the person to have reviewed the report in the first place (if it existed at all).

“In making her lurid claims, she ignores contrary information provided by members of Mr Versace’s family, who were in the best position to know the facts of his life.”

Those who were in the Versace villa the morning he died also dispute facts in the drama’s version of events. As an investigative reporter, I covered Versace’s murder in the mid-1990s and recently travelled between Miami and Rome to talk to the people who were around him at the time of his death.

I had previously met Antonio D’Amico, Versace’s partner, now 59, but he had always refused to discuss the case. In the wake of the drama being broadcast, however, he finally agreed to talk to me about that day.

He told me the drama is in stark contrast to the actual events as he remembers them. “What is depicted is not what happened that morning,” he explained, saying that he never once touched Versace’s body, so therefore was not covered in blood as Ricky Martin is in the opening scene. “It is an inaccurate portrayal of [Gianni], of that day and of how we were as a couple.”

“Significant parts of the [series] do not reflect the reality of the events that took place. I feel – together with those who know me well – that my character… is a misrepresentation of myself and what our relationship was like.”

D’Amico only met Martin, who plays him, after filming was finished.

The drama also suggests that D’Amico regularly procured young men for himself and Versace, any of whom could have given the designer HIV. D’Amico has declared that he does not have HIV as proof that Versace didn’t either.

Others around him also suggest that there is no way Cunanan could have stalked Versace and learnt his daily routine, as is depicted in the TV series. According to Charles Podesta, Versace’s butler at the time, they had only just arrived in Florida from the designer’s couture show in Paris. Podesta remembers the details of that morning.

“Gianni stopped by the kitchen to say he wasn’t eating first, as usual,” Podesta told me in an interview in Miami last December. “Instead, he was going to the corner for some magazines.”

That wasn’t his usual routine. His staff regularly brought the morning papers to the outdoor table where he and D’Amico ate breakfast by the swimming pool. He also remembers the distinct sound of gunfire that followed, “a strange noise, several loud pops one after the other”. And it was he, Podesta, who called 911.

While such details may seem banal, in the bigger picture they do beg the question: what other lines have been blurred, by Orth and the programme-makers, between fact and fiction?

American Crime Story: Why did Gianni Versace die?