A suspect in a case that has horrified and perplexed Italy for almost 19 years has been summoned for questioning by prosecutors, in a development that could expose one of the country’s most significant miscarriages of justice and free the person who has spent more than a decade in prison for the crime.

Andrea Sempio is accused of killing Chiara Poggi, a 26-year-old economics graduate, at her home in Garlasco, a small town close to Milan in northern Italy, on 13 August 2007, allegedly because she rejected his sexual advances.

Sempio, who has denied all allegations against him, is expected to appear before prosecutors in Pavia on Wednesday. However, his lawyers have said in a statement to the Italian press that he “will exercise his right to remain silent” owing to the investigation not yet being concluded.

Prosecutors reopened the murder case last year, placing Sempio, who was friends with Poggi’s brother Marco, under investigation after fresh tests on traces of DNA found under her fingernails were compatible with his.

It was initially suggested that Sempio might have allegedly carried out Poggi’s murder with others, potentially including her boyfriend at the time, Alberto Stasi, who was convicted of the crime in 2015 – after twice being acquitted – and is serving a 16-year sentence.

But prosecutors now claim that Sempio, who is formally charged with voluntary manslaughter and aggravating circumstances of cruelty, killed Poggi by himself, allegedly striking her head and face with a blunt object at least 12 times. They are now moving to have Stasi’s conviction overturned.

Described as the “delitto di Garlasco”, or Garlasco murder, the complex case and all its twists and turns has been consistently pored over by the Italian media for years, dominating crime talkshows and, more recently, podcasts.

It was Stasi, at the time a 24-year-old university student, who found Poggi’s body lying in a pool of blood on the staircase of her family home.

Police immediately identified him as the prime suspect, arguing that his shoes were far too clean for someone who had just chanced upon her body. They believed he must have washed his shoes after murdering her. Detectives claimed Poggi knew her killer because she opened the door of her home in her pyjamas. No murder weapon has ever been found.

Stasi was tried and acquitted twice, only to then be convicted on circumstantial evidence, including traces of Poggi’s DNA found on the wheels of a bike belonging to his family. The 42-year-old has always maintained his innocence, but has divided public opinion.

Giada Bocellari, one of Stasi’s lawyers, said: “Alberto was ultimately convicted not so much because of the evidence, but because of the fundamental question posed in this trial: if he didn’t do it, then who did? Since there are no reasonable alternatives, it must have been him.”

A previous investigation into Sempio was shelved in 2017 because prosecutors at the time deemed the evidence against him was insufficient. Alongside the latest investigation, Sempio’s father and a Pavia prosecutor are under scrutiny for an alleged exchange of bribes aimed at getting the case dropped. Both have denied the allegations.

Prosecutors are planning to close their investigation soon, with Sempio most probably facing trial.

“This is definitely a unique case in Italy,” said Bocellari. “Now we’re waiting for the investigation to conclude and to get the complete picture of [all the evidence] regarding Sempio so that we can, above all, see if there are any elements that definitively remove Stasi from the crime.

“We are being prudent … but this could potentially be the most serious miscarriage of justice ever committed in Italy. As far as I know, it is the first time a [murder] investigation has been reopened with a convicted person in prison.”

Lawyers for Sempio declined to be interviewed on Tuesday.

With many errors made at the start of the initial investigation, Poggi’s killing is reminiscent of the murder of Meredith Kercher, the 21-year-old British exchange student who was found stabbed to death at her home in the Umbrian city of Perugia in November 2007, months after Poggi was killed.

American Amanda Knox and her Italian boyfriend at the time, Raffaele Sollecito, spent four years in prison after initially being convicted of Kercher’s murder. They were both definitively acquitted in 2015. Rudy Guede, a third person convicted of complicity in the murder, was released from prison in 2021 after serving 13 years of a 16-year sentence.

As with Kercher, Poggi has been forgotten amid “the media circus”, Bocellari said.

However, her family has been against the reopening of the case. “The Poggi family is completely aligned with the Italian justice system, in that the final verdict is that Stasi is the culprit,” said Gianluca Zanella, a journalist and author of a book about the case, Nel Sangue di Garlasco. “They are sceptical about new investigations.”

On more than one occasion, some lawyers involved in the case have been told not to speak to the press or post on social media, or at least exercise restraint, but that has hardly been adhered to, even more so since the investigation was reopened.

“This is the first [murder] case in Italy that has seen the active involvement of the likes of YouTube channels and informal information outside of traditional media,” said Zanella. “We then risk finding ourselves with an innocent person in jail or a victim who has not received full justice.”

After the case was reopened, Stasi was given “semi-freedom” from prison, allowing him to leave for work during the day before returning to his cell at night.

Even if his conviction is overturned, the process towards that outcome will be lengthy, and it will be difficult for him to shake it off. “He will always carry the mark of a murderer for many people, regardless of how things go,” said Zanella.