The sister of murdered British aid worker Margaret Hassan claimed that the man accused of her murder went missing just before his retrial.
Ali Lutfi Jassar was given a life sentence at Baghdad's Central Criminal Court last June for his part in her abduction and murder and for attempting to blackmail her relatives.
He was due to appear in court for retrial tomorrow.
But Deirdre Manchanda, Mrs Hassan's sister, said last night she had been told that Jassar went missing from the prison facility in Iraq where he was being held.
Mrs Hassan, 59, the director of humanitarian group Care International in Iraq, was taken hostage on her way to work in Baghdad in October 2004 and shot dead just under a month later.
Mrs Manchanda explained: "We have just received the very disturbing news that Jassar cannot be located in the prison facility in which he was being held.
"The Assistant Director General of the prison has confirmed that he cannot locate him.
"Our lawyer in Baghdad expressed his concerns sometime ago about ALJ's non-appearance at any of the Appeal Hearings."
Mrs Hassan was one of the highest-profile figures to fall victim to the wave of kidnappings which swept Iraq after the 2003 US-led invasion.
The Dublin-born Roman Catholic, who had joint British, Iraqi and Irish nationality, was married to an Iraqi and had lived in Iraq for 30 years.
A Foreign Office spokeswoman said: "We stand by to provide consular assistance for Margaret Hassan's family, and want justice to be done for this dreadful crime committed against someone who dedicated her life to helping all Iraqis."