On the evening of 11 December 2006, a fire broke out in an apartment at 25 Via Armando Diaz in Erba, in the province of Como, Italy. Firefighters who extinguished the blaze found four bodies inside the building: Raffaella Castagna, 30; her mother, Paola Galli, 57; Castagna's two-year-old son, Youssef Marzouk; and neighbour Valeria Cherubini, 55. Cherubini's husband, Mario Frigerio, was found badly injured on the landing with a slashed throat; he survived because a congenital malformation of his carotid artery kept him from bleeding to death. Investigators determined that Castagna and Galli were killed in the hallway of Castagna's apartment with a crowbar and knives, that Youssef Marzouk died on the living-room sofa from stab wounds including one that severed his carotid artery, and that Cherubini, attacked on the condominium stairs, later died of carbon monoxide inhalation after the apartment was set on fire to conceal the crime. Forensic examiners concluded there had been two attackers, one of whom was left-handed.
Investigators first examined Castagna's husband, who was in Tunisia visiting his parents at the time of the killings; his alibi was confirmed and he was cleared. Attention then turned to neighbours Olindo Romano and his wife, Rosa Bazzi, who had a history of disputes with Castagna's household, including a civil case with a hearing scheduled two days after the killings. Police noted the couple's lack of concern in the aftermath, injuries consistent with a struggle, and a McDonald's receipt they offered unprompted as an alibi for a period two hours before the killings. Romano and Bazzi were arrested on 9 January 2007 after questioning, and on 10 January each separately confessed to magistrates, describing details investigators said could only have been known by the perpetrators. A blood trace matching one of the victims was later found on the door sill of the couple's car. At trial, both defendants retracted their confessions and denied guilt; Mario Frigerio, the sole surviving witness, testified and identified Romano as his attacker, having initially described his assailant differently from his hospital bed.
The Court of Assizes of Como convicted Romano and Bazzi of aggravated multiple homicide on 26 November 2008, sentencing both to life imprisonment with three years of solitary confinement. The Court of Appeal of Milan upheld the sentences on 20 April 2010, and the Supreme Court of Cassation rejected further appeals on 3 May 2011, making the convictions final. Romano and Bazzi, and separately Castagna's husband, pursued appeals to the European Court of Human Rights in 2012; all were declared inadmissible. Castagna's husband later reversed his earlier position and said he believed Romano and Bazzi were innocent; in March 2023 a court found he had defamed Castagna's brothers by suggesting in an interview that their family bore responsibility for the killings, and ordered him to pay 70,000 euros in damages. Requests to reopen the case continued for years, including a 2023 review request filed by a deputy attorney general who was later formally censured for filing it without authorization from his office. On 10 July 2024 the Court of Appeal of Brescia rejected a request for review, finding no new evidence, and the Court of Cassation closed further appeals on 25 March 2025, leaving the convictions in place. Romano and Bazzi remain in separate prisons and are permitted to meet once a month.