Zardad moved to Britain in 1998. He denies charges of conspiring to kidnap and torture civilians when he was an alleged warlord in Afghanistan, between 1991 and 1996.
Attorney-General Lord Goldsmith, speaking at the trial's opening on 8 October, said that "There are some crimes which are so heinous, such an affront to justice, that they can be tried in any country."
And that's what makes this trial unique. Rosanna Mesquita is U.K. legal adviser of Redress, a human rights organization that helps torture survivors obtain justice and reparation.
"The reason why it's so unique is that under U.K. law, the acts making up the charge did not occur in the U.K., and that the person being accused is not a U.K. national. It's not unusual in the international arena. In the U.K., usually courts try people for acts that had happened within in the U.K.," Mesquita says.
Andrew Hogg is a specialist working for The Medical Foundation for the Care of Victims of Torture in London.
"I don't believe that there has ever in a British court before been somebody brought to trial for crimes of the magnitude this man is accused of committing abroad. It could be that there has been one or two Nazi war criminals," Hogg says.
Attorney-General Goldsmith said that Zardad -- also known as Zardad Khan -- controlled checkpoints in the area of Sarobi on the Jalalabad road some 80 kilometers from Kabul. Goldsmith accused him of using "indiscriminate and unwarranted violence on innocent civilian travelers" often beating, shooting, and killing them.
The attorney-general went on to allege that "a 'human dog' [a wild man] would be set upon these civilians, biting and attacking them, to further the fear and terror. Men would be beaten with rubber hoses and strung up until they 'lost their functions' and were kept in dark rooms for months at a time."
Hogg adds that the victims were not only Afghans.
"The suggestion made very strongly to us when we were researching this was that he was in fact an accomplice of [renegade warlord] Gulbuddin Hekmatyar, and the people to bear the brunt of his bestiality were non-Muslims. Particularly Hindus and Sikhs who were going overland from Kabul back into Pakistan or vice versa," Hogg says.
British law has required that the case against Zardad be based on a United Nations Torture Convention.
Mesquita's group has followed the case closely for the past two years. She tells RFE/RL that the group has worked to facilitate communication between alleged victims and witnesses and U.K. authorities.
In yet another unusual twist, many of those witnesses, Mesquita says, are expected to testify at the trial through a video link from the British Embassy in Kabul.
"This is a cost-effective exercise, because otherwise the alternative would have been to have brought victims from overseas, which may result in difficulties for the authorities, and also delay the trial somewhat. Video link is becoming much more common and, for example, it's been used by the International Criminal Court," Mesquita says.
A jury of eight men and four women is trying Zardad. Mesquita says fairness is well-known feature of British courts.
"The U.K. courts are known for their fairness, and this court and the authorities also have to abide by the Human Rights Act. And, in particular Article 6 -- right to a fair trial. So it'll always be open to the defendant to challenge any unfairness to his trial, and I am sure that the authorities have examined and assessed all witness evidence," Mesquita says.
Hogg, for his part, says his organization will be tracking the trial with great interest.
"We'll be following what the outcome of the case is, because it will be, of course, of interest if a man gets convicted in this country for torture carried out abroad," Hogg says.
Zardad's defense lawyer has urged jurors to keep an open mind about the allegations. But with the high-profile figure of Goldsmith prosecuting the case for the government, that may prove difficult.
The attorney-general said yesterday that several witnesses would provide evidence of torture -- and worse -- at the hands of Zardad and his henchmen. The trial is expected to last a month or longer.