Human Rights Watch says the families of five political activists on trial in the United Arab Emirates have made a joint plea for their release. The men were detained six months ago for publicly insulting the country's leaders.

The New York-based rights organization says the families have sent a letter to the president and vice president of the UAE and the crown prince of Abu Dhabi, stating that the judiciary, prosecution and prison officials have violated 20 human rights standards in their treatment of the accused.

The violations include the right to a speedy and fair trial, the presumption of innocence, the right of appeal and the right to conduct sufficient questioning of prosecution witnesses to prepare and present a proper defense.

The families say UAE authorities have done nothing to stop a campaign of intimidation, including death threats against the defendants and one of their lawyers.

The activists refused to appear in court last week, saying they believed a guilty verdict had already been decided for them.

HRW says the plea from the families states authorities have held the defendants in solitary confinement for extended periods and have prevented the men from obtaining adequate medical care and treatment. The families say the detainees have been held under conditions depriving them of natural light, recreation time and exercise.

If convicted, the Emirati nationals are facing up to five years in prison.

One of the accused, prominent blogger Ahmed Mansoor, faces additional charges of inciting others to break the law, advocating an election boycott and promoting demonstrations.