Iran's reformist President Mohammad Khatami has publicly questioned Iran's judges over their handling of the investigation into the killing in custody of a Canadian journalist.
Zahra Kazemi's death has sparked a feud between reformists and hardliners
An intelligence ministry interrogator went on trial on Tuesday, accused of killing Zahra Kazemi, but President Khatami has cast doubt on the proceedings and called for them to be corrected.
"We are asking for nothing else than impartiality, and we think that there should be an impartial trial that is not influenced by the very same people who rank among those who have been accused in the affair," he said.
The BBC's Jim Muir, in Tehran, said Mr Khatami has followed closely the case which has implications for human rights in the country and that has also aggravated tensions between reformists and hardliners.
Ms Kazemi, 54, was detained on 23 June for taking pictures of Tehran's Evin prison.
She died in hospital in Tehran on 10 July after falling into a coma having received head injuries during more than three days of interrogation.
Our correspondent says the case has sparked a bitter feud between the highly conservative judiciary and the largely reformist Intelligence Ministry.
Between her arrest and her admission to hospital, the journalist spent four days moving between the custody of prosecutors of the judiciary, police and the Intelligence Ministry
Mr Khatami is a reformist figure
It is one of the ministry's interrogators who has being accused by the judiciary of dealing the blow which killed Mrs Kazemi.
But President Khatami clearly cast doubt on the prosecution, saying he said it was essential to identify who had carried out the action.
The procedure of the case, he said, had not been correct, and he hoped the head of the judiciary would amend it.
"Why were all the people who were implicated in this affair... not interrogated?" Khatami told reporters after a cabinet meeting.
This was a reference to Tehran Chief Prosecutor, Judge Said Mortazavi, our correspondent says.
Judge Mortazavi personally interrogated Mrs Kazemi early in her detention.
The Intelligence Ministry has already challenged the indictment of its interrogator, saying the charges ignored testimony that Mrs Kazemi had been beaten while in the custody of judiciary officials.
The ministry has promised to hold a news conference to lay out its version of the truth.