Iran's Supreme Court has ordered a new investigation into the death of the Iranian-Canadian photojournalist, Zahra Kazemi, while in custody in 2003.
Zahra Kazemi died in a hospital in Tehran in July 2003
Judiciary spokesman Ali Reza Jamshidi said the court had objected to the acquittal in 2004 of an intelligence agent accused of beating her to death.
He said judges had "found some formal flaws" in previous investigations.
Kazemi, 54, died in Tehran in July 2003 having received head injuries during more than three days of interrogation.
She was arrested on 23 June 2003 while taking photographs outside Evin prison in the north of the capital, but was never formally charged with any offence.
The case severely strained relations between the Canadian and Iranian governments.
An Iranian presidential inquiry initially conducted into the journalist's death found that Kazemi had been killed by a "physical attack" while being held in custody in June 2003.
In September 2003, the judiciary charged an intelligence ministry agent, Mohammad Reza Aghdam Ahmadi, with "semi-intentional murder". He pleaded not guilty at the opening of his trial a month later.
At the trial, lawyers representing Kazemi's mother, including the Nobel Laureate, Shirin Ebadi, alleged that a senior prison official named Mohammad Bakhshi, not Mr Ahmadi, had tortured and killed the journalist in a premeditated way.
Mr Ahmadi was eventually acquitted in July 2004 "due to lack of sufficient evidence", a ruling that prompted the judiciary to conclude that Kazemi's head injuries could only have been the result of a fall caused by a drop in blood pressure brought on by a hunger strike.
Zahra Kazemi was interrogated at Tehran's notorious Evin prison
In July 2005, a higher court rejected an appeal to investigate the death, saying it had no jurisdiction to reopen the case.
However, four months later an appeals court ordered the case to be reopened and upheld Mr Ahmadi's acquittal.
Speaking to reporters on Tuesday, Mr Jamshidi said the verification branch of Iran's Supreme Court had reviewed the lower courts' rulings and ordered a new investigation to be undertaken by the judiciary.
"The verification branch found some formal flaws and had an objection regarding the jurisdiction of the court that dealt with the case," he said.
"The file has been sent to the competent authority for investigation."
One of the lawyers representing Kazemi's mother, Mohammed Seifzadeh, said he was hopeful the new investigation might lead to new charges in the case.
"This is a decision in the right direction. Now, we want a full, free and fair reinvestigation into the deliberate murder of Kazemi," he told the Associated Press news agency.
But the Canadian lawyer representing the dead journalist's family, John Terry, said her son, Stephan Hachemi, did not place much value on the Supreme Court's ruling.
"He knows the truth already. He knows that Iranian officials have tortured, raped and murdered his mother. Until the Iranians are willing to recognise that and hold those accountable for that he's not going to see this as an important development," Mr Terry said.
"I don't see it going anywhere," he added. "We don't have confidence in the Iranian system. We've seen one trial that resulted in essentially a whitewashing of Iranian officials."
In March 2005, Shahram Azam, a former doctor at the Iranian defence ministry who examined Kazemi four days after her arrest, said the journalist showed obvious signs of having been tortured and brutally raped by her interrogators.
The BBC was also told by medical staff at the military hospital where Kazemi died that she would have survived the beating given to her had doctors been allowed to treat her earlier.
The Canadian government has repeatedly demanded that Iran agree to an international investigation into the journalist's death.