The trial of a US soldier charged with the murder of an Italian intelligence agent in Iraq in March 2005 has begun in a Rome court.
Mr Calipari died after rescuing a journalist held hostage
The soldier, Mario Lozano of the 69th Infantry Regiment, is not attending the trial, but in Italy the defendant can be tried in absentia.
The agent, Nicola Calipari, was shot dead on his way to Baghdad airport.
Mr Lozano is standing trial charged with murder and two counts of attempted murder. He denies the charges.
Mr Calipari was escorting Giuliana Sgrena, an Italian journalist who had just been freed by kidnappers.
As the car approached a road block, US soldiers opened fire.
US military: Car approaches checkpoint at high speed
Troops attempt to tell driver to stop with arm signals, lights and warning shots
Soldiers shoot into engine
Italian government: No warning signs to motorists about impending checkpoint
Car not speeding and did not accelerate after warning shots
Proper inquiry impossible because vehicles removed and army logs destroyed just after shooting
Calipari, who shielded the journalist during the shooting, was hailed a hero at home, awarded Italy's top bravery award and given a state funeral attended by tens of thousands.
Franco Coppi, representing Mr Calipari's widow, said the fact the American was not in court did not jeopardise the case.
"His absence is his own choice," he told reporters. "It does not represent an obstacle to ascertaining the truth. We are absolutely serene. The evidence gathered is indisputable."
Fabrizio Cardinali, Lozano's former court-appointed lawyer, told the Associated Press (AP) ahead of the trial that the incident was caused by the Italians' "lack of caution".
He told AP: "What happened was not the fault of the checkpoint, but the fault of the Italians who did not have any military escort."
Lozano's current lawyer, Alberto Biffani, said he believed his client would be acquitted.
Italy and the US drew very different conclusions over what had happened.
Calipari was honoured with a state funeral in 2005
The US military said the vehicle was travelling too fast, alarming soldiers, who feared it was an insurgent attack.
Italian officials claimed the car was travelling at normal speed and accused the US military of failing to signal there was a checkpoint.
Mario Lozano, both countries agree, fired the fatal shots.
He has told newspapers he had little choice but to open fire.
Explaining the rules of an engagement at a roadblock, he said: "You have a warning line, you have a danger line, and you have a kill line."
The soldier said he flashed a spotlight at the vehicle as it approached, then fired warning shots, and then fired at the engine.