Schoolgirl's murder that has Italy totally transfixed
When 13-year-old Yara Gambirasio disappeared near her home in 2010, it set in train an investigation that reaches its climax this spring.
It is the criminal investigation that has obsessed Italy. The disappearance of a 13-year-old girl, a tragedy for a small town and a highly controversial investigation in which cutting-edge techniques have shed light on hidden infidelities and stirred up age-old prejudices.
What began as the search for a missing schoolgirl grew into a man-hunt that seemed cursed to find one dead-end after another - until investigators launched what may be the largest DNA dragnet in criminal history.
And even now, with a suspect finally due to go to trial, his defence lawyer has promised at least one final twist, a witness he claims will fatally damage the case for the prosecution.
It began on the evening of November 26, 2010, when Yara Gambirasio went missing in the small town of Brembate di Sopra in northern Italy.
She had left her family home at 5.15pm to go to the local municipal sports centre for her regular gymnastics class. The gym was just a short walk away. When Yara had not returned by 7pm, her parents tried to call her on her mobile phone. When they failed to get an answer, they alerted the police.
Officers in the regional capital, Bergamo, immediately sent several teams, both local and state, to Brembate di Sopra, in the foothills of the Alps an hour north of Milan.
The town has only 8,000 inhabitants. Yara's gymnastics teacher told the police that she had done some light training and left shortly after 6pm. Yara had texted a friend at 6.44pm to arrange a meeting the following Sunday and that was the last anybody had heard from her.
It was the start of a three-month search for Yara, during which her family, including her parents Fulvio and Maura (an architect and a teacher in a nearby school), were questioned by detectives who also talked to virtually every inhabitant of the town. The Gambirasio family (Yara had an older sister and two younger brothers) appeared to be solid, happy, unexceptional.
A handful of witnesses could provide only vague statements. Tracker dogs followed a path in the opposite direction to the street which would have brought her home, tracking a scent towards the nearest village, Mapello. When the police checked, they confirmed that Yara's phone had last been registered in Mapello, before it went "dark".
The local investigating magistrate, Letizia Ruggeri, a 45-year-old former policewoman who began her career investigating the Cosa Nostra in Sicily, immediately ordered the checking of records of more than 15,000 mobile phones registered in Yara's home town and the nearby villages. The investigator also ordered wiretaps on hundreds of phones used by potential suspects.
They turned up a conversation, recorded several weeks after the disappearance, in which a Moroccan-born man called Mohammed Fikri was thought to have said: "Forgive me lord, I did not kill her".
Fikri had been working in a builder's yard in Mapello, the village in which Yara's phone was last registered. Police intercepted him as he was about to board a ferry bound for Tangiers in early December. A mattress in the back of his van was found to have blood stains on it. However, though he was held and questioned and many in the media (and some police) believed they had their man, the investigators quickly cleared Fikri.
As the investigation continued, Yara was still classed as missing. Her parents, very private people who were shocked to be in the national media spotlight, made an appeal for information at Christmas.
However, it was not until the afternoon of February 26, exactly three months after she had disappeared, that a local man stumbled across the badly decomposed and partially frozen remains of a young woman on scrubland outside the nearby village of Chignolo d'Isola.
It was Yara. She had suffered multiple stab wounds and was partially undressed. But later examination concluded she had not been sexually assaulted. And Yara had not died of her wounds. Examiners concluded that she had been dumped, seriously injured, in the open and had died of exposure.
The investigation moved up a gear as Magistrate Ruggeri faced increasing pressure and vilification from many, including local right-wing politicians who stated publicly that a woman, and a southern Italian woman at that, could not handle the case.
With virtually no leads, Ruggeri and her team decided on a drastic course. A DNA sample had been recovered from Yara's remains. The team would use it to launch what may be the largest forensic DNA dragnet ever carried out by a police force. Some 15,000 voluntary DNA tests were carried out on virtually every adult male (and many women) living in the area.
Giorgio Portera, a former police lieutenant turned geneticist, who was employed as a consultant by the family of the dead girl, told reporters: "Nothing so large had ever been attempted anywhere in the world before, let alone Italy."
It was, as Rome daily newspaper Il Foglio put it, "an operation perhaps without precedent in the field of criminology and jurisprudence - the genetic screening of an entire territory".
Some sections of the Italian media labelled it an act of desperation. And there were questions raised about the risks to privacy and the characterisation of all locals as suspects. What the investigators were hoping for was a fresh lead.
The tests included DNA samples taken from men who frequented a nightclub near the field where Yara's body was found. One was from a local man called Damiano Guerinoni, whose DNA turned out to be very similar to that recovered from the body of the dead girl.
Guerinoni was quickly ruled out as a suspect, he had been in South America at the time of the murder. But forensic scientists working in labs in Rome told the police that he had to be a close relative of the man they were looking for.
Further tests of the wider Guerinoni family narrowed the lead to an uncle, Giuseppe Guerinoni. But there was one problem - Giuseppe had died 11 years before the murder.
Police went to his widow and were able to find an old application for a driving licence with a stamp that had been licked by the dead man. They were able to extract DNA samples from the residue of the saliva - and later from the exhumed body of the dead man - that proved Giuseppe Guerinoni was the father of the man whose DNA had been found on the dead girl.
However, while the dead man had three living children with his wife, they were all quickly excluded as suspects. The investigators now arrived at one conclusion. Giuseppe Guerinoni had a secret son, and he was the man they were looking for.
Now the police had to track down the illegitimate child of a dead bus driver. They had to find the woman with whom he had secretly fathered a son.
They questioned all of Giuseppe's friends and family, to build a picture of his life. Some friends acknowledged that he was a ladies' man, but few if any in the small, close-knit communities in the mountain regions were willing to give details.
After months of painstaking investigation, the police compiled a list of 532 women who would have been known to the dead man and could have possibly had a sexual relationship with him.
They DNA tested them all, first in 2012 to 2013 and then again in 2014.
The sample of one of the women, 67-year-old Ester Arzuffi was found to be a perfect match. If the police theory was right, she was the mother of the killer.
Arzuffi had been married to the same man - Giovanni Bossetti - since 1967, when she was 19. The family, who have three children, still live in Brembate di Sopra, Yara's home town.
But the DNA evidence proved that her eldest twins, Massimo and Laura, were not fathered by her husband but by Giuseppe Guerinoni.
Massimo Bossetti was tested (using a fake drink-driving checkpoint set up on the edge of the village) early last summer and found to be a perfect match to the original DNA sample. The test showed 21 compatible markers (16 to 17 are usually considered to be enough in Italian law).
Bossetti, an apparently happily married 43-year-old carpenter with three young children, has been charged with the murder of Yara and will stand trial this spring.
He has said nothing beyond proclaiming his innocence. His lawyers have said that while the DNA may match, he has no idea how it got on the dead girl and it does not prove he killed her. They have also claimed this week to have a witness who can refute prosecution claims that he was in the area when the murder happened.
It has been a tortuously complex investigation with many twists and turns. And Italians, grimly fascinated by what has happened so far, await the next chapter.