Two US students appeared in an Italian court on Wednesday on the first day of their trial over the fatal stabbing last year of a policeman during a botched drugs bust.
Finnegan Lee Elder and Gabriel Natale-Hjorth are charged with killing newlywed Mario Cerciello Rega, 35, who was stabbed 11 times last July.
The Californians, who had been on holiday in Rome and were both teenagers at the time, face life sentences if convicted.
Elder, now 20, was wearing a blue-plaid shirt under a jacket and mouthed "I love you" to his parents, who were sitting in the back row of the courtroom, which was packed with journalists.
Natale-Hjorth, 19, whose parents were not in court, sat directly in front of the policeman's widow, who was accompanied by family members. Both young men were flanked by prison guards.
Neither of the defendants spoke on Wednesday's opening day of the trial which will continue next month.
- Major blunders -
In Italy, the slaying aroused an outpouring of public sympathy for Cerciello, who had just returned from his honeymoon when he was killed.
Huge crowds attended his funeral -- which was broadcast live on television -- where he was hailed as a hero.
Cerciello's wife, Maria Rosario Esilio, who is a civil party to the case, has said the murder of her husband "cannot and must not go unpunished."
But the case has also been marked by major blunders -- especially the blindfolding of Natale-Hjorth during his police interrogation -- and contradictory statements made by a key prosecution witness, Cerciello's police colleague Andrea Varriale, who was in court Wednesday.
In the aftermath, Varriale said he and Cerciello had been attacked by men of North African descent. He also initially claimed he had been armed.
Both officers were in fact unarmed and acted without backup, in violation of police procedure.
Amid the intense media focus in the case, comparisons have been made to the high-profile trial of Amanda Knox, a US student convicted and later acquitted of a 2007 murder in Italy.
Wednesday's hearing was procedural, with the defence asking the court to limit the number of civil parties seeking damages and each side asking that key elements of their case be allowed into evidence.
Elder looked dazed as he was led out during a break.
"He is very tired and stressed, and has requested to be excused from the rest of the hearing today", his lawyer Renato Borzone told AFP, after asking the guards escorting Elder out to allow him a moment with his parents.
Elder has admitted to stabbing Cerciello with a 7-inch (18 cm) serrated-edge combat knife he had stashed in his sweatshirt but told investigators he thought he and his friend were being set upon by drug dealers.
"We hope that this trial can stay focused on the facts of what happened that night," the Elder family said in a statement on Wednesday.
"We look forward to the truth coming out and to Finn coming home."
- 32-second attack -
During the investigation, the young men and Varriale gave opposing versions of what happened during the 32-second attack in the early hours of the morning, which followed a botched drug deal.
Hours earlier, the teens from the San Francisco Bay Area had gone looking for cocaine in the popular night-life area of Trastevere. Intermediary Sergio Brugiatelli introduced them to a dealer who sold them aspirin instead.
In retaliation, the teens stole Brugiatelli's bag, before demanding money and drugs to return it.
Cerciello and Varriale went in Brugiatelli's place to the designated exchange point in an upscale neighbourhood near the teenagers' hotel but the handover never took place.
Elder told police they were jumped from behind by the officers and believed they were thugs sent by Brugiatelli.
Varriale has said he and Cerciello, both in plain clothes, told the young men they were police, but that Elder pulled out a knife and attacked Cerciello, while Natale-Hjorth wrestled with Varriale.
The teens then fled to their nearby hotel, where police later found the military knife hidden behind a ceiling panel.
Under Italian law, Natale-Hjorth faces the same charge of "voluntary homicide" with a special circumstance of killing a police officer, even though he did not stab Cerciello.
On Wednesday, one of Natale-Hjorth's attorneys, Fabio Alonzi, said the defence sought a copy of the video of his client, blindfolded and handcuffed, during his police interrogation. The video "apparently was modified" after it was filmed by Varriale, Alonzi said. Excerpts were leaked to reporters.
Both young men are also charged with attempted extortion. They face a maximum penalty of life imprisonment in isolation.
The court set a next trial date for March 9.