The body of Tarek Hassan was discovered north of Baghdad in September 2003. His hands were tied and he had been shot dead with a Kalashnikov rifle.
Hassan had been arrested by British soldiers in April 2003, shortly after the US-led invasion of Iraq, and held at Camp Bucca in southeastern Iraq. But Britain says he was released the following month.
His brother, Khadim Hassan, brought the case to the European Court of Human Rights in Strasbourg, claiming the detention was illegal and the British were responsible for the death and signs of torture found on Tarek's body.
But the court rejected the claims, saying "there had been legitimate grounds under international law for capturing and detaining Tarek Hassan, who had been found by British troops, armed and on the roof of his brother’s house, where other weapons and documents of a military intelligence value had been retrieved."
Before the invasion, Khadim Hassan was a general in Saddam Hussein's private El Quds army and a senior official in the ruling Ba'ath Party.
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He told the court he went into hiding after the invasion, leaving his brother to guard the family home. He argued the British had taken his brother hostage in a bid to draw him out of hiding.
But the court accepted evidence from the British government that Tarek had been subjected to a screening process, found to be a civilian and released long before his death. It said there was no evidence he was ill-treated during his detention.
Britain said it had no idea what happened to Tarek after his release in May 2003, and that British forces did not use Kalashnikov rifles.
The family argued it had received no word from him after his supposed release, and that he was still carrying a Camp Bucca identity card when he was killed.