Court documents suggest the FBI paid a Geek Squad technician who located images of child abuse on a customer’s computer $500 (£412).
Companies that carry out computer repairs are legally required to report such images, but a warrant is required for actively searching for material.
Defence lawyers argue that the FBI was directing the technician to look for illegal activity.
Geek Squad’s parent company, Best Buy, and the FBI have denied any wrongdoing.
Defence lawyers claim that the FBI had had eight “confidential human sources” in the Geek Squad, according to the Washington Post, which first reported the story.
The case has led online tech publication Network World – which declared the practice “unconstitutional” – to call for users to boycott Best Buy.
The case stretches back to November 2011 when an image of a young naked girl was found on the hard drive of Californian doctor, Mark Rettenmaier.
His lawyers want the case thrown out, arguing that the image was gleaned from an illegal search.
The FBI claim that a later search of Dr Rettenmaier’s iPhone found 800 images of naked girls.
Defence lawyer James Riddet claimed in a court filing last month that “the FBI was dealing with a paid agent inside the Geek Squad who was used for the specific purpose of…
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