Iran's political prisoners worry the international community
The trial has begun in a closed revolutionary court in Tehran of a veteran political activist, Ezatollah Sahabi.
The judiciary is controlled by Conservative clerics
He is the first of a group of 15 members of a loose liberal alliance to appear in court on charges of plotting to overthrow the Islamic regime.
The prosecution has been strongly condemned by international human rights organisations and by reformist leaders in Iran itself.
Mr Sahabi, who is in his 70s, is a veteran struggler for democracy, who enjoys the not-unique distinction of having been imprisoned both under the Shah and under the Islamic Republic.
This time he has been held without trial for more than a year after a speech in which he told university students that a system based on political repression could not survive.
Human rights concern
His appearance at this first session of his trial took place under tight security - behind closed doors at the revolutionary court, in which the judge acts as both prosecutor and jury.
Khatami's reformist government says there is no proof of Sahabi's guilt
It is understood that this hearing consisted largely of the charges being read out - the indictment is apparently so long it is to be resumed in a few day's time.
The manner of both the trial and the detention of Mr Sahabi and several others of these so-called national religious activists has been strongly criticised by human rights groups around the world, as well as by reformists at home.
Five of the accused are being held in a secret Revolutionary Guard jail outside the regular prison system. Remand proceedings have not been followed.
The Intelligence Ministry, which comes under President Khatami's reformist government, has said it has no evidence to support the charge that Mr Sahabi and others were plotting to overthrow the regime.
The judiciary, which is generally seen as a bastion of right-wing power, is independent both of government and parliament.
Mr Sahabi has already been through a lengthy trial process relating to his participation in a controversial conference in Berlin two years ago.
He was initially given a four-and-a-half year-sentence for that, but it was eventually reduced to just six months.
In addition to Mr Sahabi and his 14 national religious colleagues, more than 30 associates of the like-minded Freedom Movement are on trial in a similar prosecution.
They were arrested in successive waves last year in what was widely seen here as the latest crackdown by entrenched hardliners determined to counter the election victories of the reformists.