"They beat me pretty bad" said Finnegan Lee Elder.

An American student on trial in Italy for the murder of a Rome policeman claims he was kicked, punched and spat on in custody, according to a leaked official transcript from last summer, reports AFP.

Finnegan Lee Elder and fellow Californian student Gabriel Christian Natale-Hjorth could be handed life sentences if convicted of murdering Mario Cerciello Rega, a 35-year-old carabiniere who was stabbed 11 times in Rome last July.

Cerciello Rega and his colleague Andrea Varriale, both dressed in plain-clothes, had gone to investigate a drug deal gone wrong in the capital's upmarket Prati district in the early hours of 26 July 2019.

While in Rome's Regina Coeli prison on 2 August, Elder was recorded secretly during a private conversation with his father and American lawyer. "They beat me pretty bad ... in the [police] station," Elder said in a transcript of the conversation requested by the court, reports AFP.

"They threw me to the ground, kicked me, punched me, stood on me, spit on me" - he said - "They said they would give me 40 years if I didn't give them my phone password."

Elder's claims of police brutality follow the leaking of photographs of Hjorth blindfolded and handcuffed at a police station in Rome.

"The awful truth of what Finnegan was subjected to and endured as a terrified 19-year-old is now being revealed to the world," - Elder's father Ethan told AFP - "Our hearts break every minute of every hour of every day."

• US students in court in Rome over police murder

Elder, now 20, has admitted to stabbing Cerciello Rega with an 18-cm serrated-edge combat knife but has insisted to investigators that he thought he and his friend were being attacked by drug dealers.

What happened prior to attack

A few hours earlier Elder and Natale-Hjorth had been trying to buy cocaine in the popular night-life area of Trastevere.

A man described as an "intermediary" and identified as Sergio Brugiatelli helped them find a dealer who allegedly sold them crushed aspirin instead of drugs.

In retaliation the students stole Brugiatelli's rucksack, demanding the return of their money plus a gram of cocaine in exchange. However Brugiatelli informed the police of the situation, with undercover officers Cerciello Rega and Varriale going to the designated meeting place in Prati instead of Brugiatelli.

Elder claims that they were jumped from behind by the officers who they believed were criminal associates of Brugiatelli. Varriale has said that he and Cerciello Rega, both unarmed, told the young men they were police, but that Elder pulled out a knife and attacked Cerciello Rega, while Natale-Hjorth wrestled with Varriale.

In the ensuing 32-second brawl Cerciello Rega was stabbed 11 times, later dying from his wounds in nearby S. Spirito hospital.

Elder and Natale-Hjorth fled the scene but were tracked down the next day to a hotel, in the same area as the attack, where police found the military knife hidden behind a ceiling panel.

Contradictory version of events

Varriale initially said that he and Cerciello Rega had been attacked by men of north African descent, as well as claiming that he had been armed. However it later transpired that both officers were unarmed and that they acted without backup, in violation of police procedure.

• Carabiniere accused of maltreating US murder witness

Shortly after the teens' arrest, a photo showing Natale-Hjorth blindfolded and restrained at a police station was leaked to the Italian media, attracting further controversy to the case.

Separately, defence lawyers for the US students say that transcripts of talks between Elder and his lawyer which were published in Italian media and suggested that he had confessed, were translated badly and appeared to omit parts of their conversation.

Outpouring of public sympathy

Cerciello Rega's murder received widespread attention in Italy where he was portrayed as a hero. He had only just returned to duty from his honeymoon, and massive crowds turned out for his funeral at the same church where he had been married just 43 days before.