Nobel Peace Prize laureate Shirin Ebadi accused Iran's hardline judiciary of prosecuting an innocent man for the killing of a Canadian journalist in order to protect one of its own officials.
Ebadi's comments are likely to fuel international concern about the transparency of the trial, which has strained Iran's relations with Canada, and heightened rifts between the reformist government and judiciary.
Photographer Zahra Kazemi died in custody after she was arrested in Tehran last July. An intelligence agent is charged with killing her.
Visibly furious, Ebadi stormed out of the courtroom at the end of the trial, and said the judge had disregarded evidence that Kazemi was dealt a fatal blow by a judiciary official inside Tehran's notorious Evin prison.
"I'm so angry I cannot speak. They didn't even pay attention to our evidence and announced the end of the trial," she told reporters outside the Tehran court.
"This is not a fair trial. The case hasn't been reviewed. If they issue a verdict it will be unfair," said Ebadi, who was representing Kazemi's family at the trial.
Lawyers said they expected the judge to announce his verdict next week.
Prosecutors have accused Intelligence Ministry agent Mohammad Reza Aqdam of what they call the semi-intentional murder of 54-year-old Kazemi, who was arrested for taking photographs outside Evin. Aqdam has denied the charge.
Even President Mohammad Khatami, siding with the reformist-run Intelligence Ministry, has said he believes Aqdam is innocent and has called on the judiciary to identify "the real guilty person".
The judiciary initially announced Kazemi had died of a stroke. But a subsequent government inquiry showed she received a blow to the head in Evin that cracked her skull and caused a brain haemorrhage.
She died in hospital, 10 days after lapsing into a coma.
Ebadi and Aqdam's lawyers said the court had ignored accounts by witnesses who said Kazemi was hit on the head by a judiciary official named Mohammad Bakhshi shortly after her arrest.
Canadian, Dutch, British and French diplomats and foreign media were barred from the court, although they had been allowed to attend on Saturday. Diplomats warned the ban would hurt Iran's human rights image.