Paul McGuigan, 37, a former Royal Marine originally from Peebles in the Scottish Borders, was gunned down alongside Australian Darren Hoare in August 2009.
Their alleged killer Danny Fitzsimons, 30, from Greater Manchester, worked alongside the two men for private security firm ArmourGroup in Iraq's fortified green zone.
A Baghdad court was expected to pass verdict yesterday, but the judge moved for yet another adjournment to consider his mental state. He could face the death penalty if he is convicted of the killing.
The case has already faced several delays while the judge considers whether to allow Mr Fitzsimons' previous diagnosis of post-traumatic stress syndrome to be allowed into evidence.
Fitzsimons is charged with two counts of premeditated murder for shooting the British and Australian contractors, and attempted murder of an Iraqi guard.
He has pleaded not guilty, claiming he was mentally ill at the time and acting in self-defence.
Mr McGuigan's fiance Nicci Prestage, 37, made an impassioned plea for the court to disregard the diagnosis, claiming there was scant evidence to support the claim.
She also said her fianc had met Fitzsimons only a few hours before his death, and refuted defence claims that they were involved in a drunken brawl.
Yesterday, the Iraqi judge set a preliminary date of February 20 for Fitzsimons' next hearing to allow him to consider further evidence.
Miss Prestage said: "It is both frustrating and upsetting to hear there will be yet another delay before we have the outcome of the trial.
"People have no idea of the agony victims and their families go through at times like this."
Friend Fiona Gordon added that Miss Prestage was "totally distraught" that her ordeal was set to drag on for another month.
She added: "The trial has been postponed so many times and she had psyched herself up for it finally being over today, but now she faces more uncertainty.
"The judge said he wants to obtain some more documents so we're waiting for them to come through. There's a possibility it could all be over earlier if the judge manages to get his hands on the documents sooner, but otherwise the next hearing is scheduled for February 20."
Miss Prestage said the extent of her fianc's injuries, two shots to the chest and a single killer shot through the mouth, amounted to an "execution".
Mr Hoare was shot through the temple at close range.