In what is thought to be a legal first, Anis Abid Sardar is being tried at London’s Woolwich Crown Court over his alleged role in the Iraqi insurgency.
Sardar, 38, from Wembley in north-west London, is accused of making bombs in Syria that were planted on a road out of Baghdad throughout 2007.
One of them is said to have caused the death of 34-year-old Sergeant First Class Randy Johnson, of 2nd Stryker Cavalry Regiment, when it hit the armoured vehicle in which he was travelling in September 2007.
Other US soldiers were seriously injured by the blast and also in a firefight while dealing with another IED that Sardar had made, the court heard.
Opening the case, prosecutor Max Hill QC told the jury: “This is an unusual trial, in that almost all of the evidence you will hear and see comes from Iraq.
“The offences, we say, are the most serious imaginable, and the British link is the fact that the defendant, a British citizen, lives and works here.
“For that reason, it is lawful to place him on trial in London, even though the activities you will hear about took place far away in Iraq.”
He added: “He seems to have been based in Syria, probably in the capital city Damascus at relevant times.”
The court heard that Sardar claims to have travelled to Syria to learn Arabic, but documents found at his London home suggested an advanced understanding of the language.
Police searching the property also found an Arabic-language bomb-making manual.
Mr Hill added: “The Crown say therefore that whilst it may be true that he was studying languages, he was without doubt involved in bomb-making, whether in Syria or in neighbouring Iraq.
“During the period with which we are concerned, namely several months during 2007, a number of bombs or improvised explosive devices were found buried under the roads leading west from Baghdad in Iraq.
“One of those bombs detonated fully as a US military vehicle passed over it, killing Sergeant Johnson.
“Several other bombs were recovered, in at least one instance after a firefight in which further US military soldiers were injured.”
Mr Hill said the devices linked to the case “were not off-the-shelf bombs – they were made with deadly intent”.
They were later taken from Iraq to an FBI lab in the US for examination by experts.
The bombs allegedly made by Sardar were found on the road from Baghdad to the notorious Abu Ghraib prison.
Two bombs were recovered which had fingerprints left by Sardar, the court heard. These devices and another two also had the fingerprints of another man, Sajjad Adnan. Mr Hill said that the two men had been working together and with others to build the bombs and plant them.
The bomb that killed Sgt Johnson was only found to have a fingerprint left by Adnan.
“That bomb was part of a sequence, involving bombs concealed geographically quite close together, all as part of a joint effort by the defendant Mr Sardar, together with Adnan and others,” Mr Hill said.
“That is why it is unnecessary for Mr Sardar to have left his own finger mark on the bomb which killed Sergeant Johnson.”
The device that killed Sgt Johnson went off when the Stryker armoured vehicle he was travelling in went down a dip in the road.
It blew a hole in the bottom of the vehicle beneath where Sergeant Johnson was standing and he took the full force of the blast, while four other soldiers were also injured.
Adnan, who is not a British citizen, was arrested after the bombings and handed over to the Iraqi authorities. His whereabouts are unknown. Sardar denies murder, conspiracy to murder and conspiracy to cause an explosion. The trial continues.