Jonathon Idema told an Afghan court on Monday the US Federal Bureau of Investigation had taken hundreds of videotapes, photos and documents from the Afghan National Directorate of Security (NDS).
The "evidence" detailed his links with the FBI, the Central Intelligence Agency, the US Defence Department and US-led forces, he said.
"In front of the judge is the receipt that the FBI signed. Why did the judge allow the FBI to take evidence from the NDS?" Idema questioned, alleging that 500 pages of documents, 200 videotapes and at least 400 photographs had been seized.
"Now it's at the US embassy where no one is ever going to see it."
Idema, wearing dark sunglasses and a khaki army shirt with a US flag on the shoulder, was in the dock with co-defendants Brent Bennet, Edward Caraballo and their four Afghan partners.
The seven men were arrested on 5 July at a house in west Kabul where they were allegedly running a private "counter-terrorism operation", apparently hoping to score the millions of dollars on offer from the FBI and CIA for the capture of top al-Qaida suspects.
Usama bin Ladin alone has a $25 million bounty on his head.
Top al-Qaida figures have huge
bounties on their heads
Idema claims he and his partners, who called their operation "Task Force Sabre 7", were working with the full knowledge of US Defence Secretary Donald Rumsfeld to hunt down suspected "terrorists".
Both the US and Afghan governments have disavowed any ties with Idema, Bennett and Caraballo.
But since Idema's first court appearance on 21 July, US-led occupation forces have admitted they took a "terror" suspect arrested by Idema into custody.
The suspect was later released after US forces found he was not a wanted fighter.
US forces duped
US-led forces said they were duped into helping Idema's team, who wore US-style uniforms, believing they were legitimate special forces operatives.
The case has shone a spotlight on the shadowy world of security and "counter-terrorism" in a country where US-led forces and other foreign troops stay close to their bases, leaving a wide swathe for private security contractors to operate.
Foreign troops believed Idema's
team was a legitimate force
The trial was adjourned after a 21 July appearance to allow three Americans and four Afghan associates a better defence, and to find adequate translators.
The seven men face jail sentences of between 16 and 20 years if found guilty.
US-led forces in Afghanistan are already under fire from rights groups for their mistreatment of detainees in Afghanistan, at least one of whom died while in custody.