If you send your laptop to be repaired, its contents may come under closer scrutiny than you expect.

A court case in California has revealed that technicians from Best Buy's repair shop, Geek Squad, have served as paid informants for the FBI. Details from the hearing reveal that its staff identified incriminating evidence in the form of child pornography on customer computers.

Many of the documents from the case, which relates to a California doctor accused of possessing child pornography, are sealed. But one former Geek Squad manager explained in a statement made available by Consumerist that “when technicians in the data recovery department found suspected child pornography on customers’ computers in such a situation, they were to stop working immediately and notify their Supervisor [who] would contact the FBI.”

He goes on to explains that he “was paid $500 in 2011 by Special Agent Tracey Riley,” but insists that he “did not understand the payment to be given as encouragement to find child pornography on behalf of the FBI.”

Best Buy told the Washington Post that if its employees come across incriminating material during their work they "have a legal and moral obligation to turn that material over to law enforcement." It added that payment by the FBI is “not something we tolerate and is certainly not a part of our normal business behavior."

But the newspaper points out that the court has seen e-mails that were sent between Geek Squad employees and FBI agents. That suggests that the situation had become an established practice, and the relationship between the two is now being investigated.

In sending a device to be repaired, customers surely acknowledge that it may be probed by the technician that works on it. But they likely don't think that they could be handing their computer to a paid agent of the federal government, and forfeiting their Fourth Amendment protection from unreasonable searches in the process. It only seems reasonable to expect the FBI to acquire a warrant before their property is searched.

That said, it’s becoming easier for such warrants to be obtained. Last year, the FBI was granted greater authority to hack into computers during criminal investigations, and Congress made it easier for investigators to obtain warrants for devices they don’t have in custody. So if you'd rather keep your files away from the eyes of law enforcers, it might pay to repair your own laptop.

(Read more: The Washington Post, Consumerist, "Congress Is About to Expand Government Hacking Powers," "Technology Can Make Lawful Surveillance Both Open and Effective")