When does a technical support service become a government search without a warrant? Defense attorneys have cried foul over an allegedly close relationship between the FBI and Best Buy’s Geek Squad after payments to technicians for uncovering child pornography on customer hard drives during repair calls. A federal court has ordered a hearing into the cultivation and payment of sources within the technology giant to determine whether the tips were in essence unlawful intrusions by investigators:

The existence of the small cadre of informants within one of the country’s most popular computer repair services was revealed in the case of a California doctor who is facing federal charges after his hard drive was flagged by a technician. The doctor’s lawyers found that the FBI had cultivated eight “confidential human sources” in the Geek Squad over a four-year period, according to a judge’s order in the case, with all of them receiving some payment.

The case raises issues about privacy and the government use of informants. If a customer turns over their computer for repair, do they forfeit their expectation of privacy, and their Fourth Amendment protection from unreasonable searches? And if an informant is paid, does it compromise their credibility or effectively convert them into an agent of the government?

Best Buy searching a computer is legal — the customer authorized it, and the law does not prohibit private searches. But if Best Buy serves as an arm of the government, then a warrant or specific consent is needed. And a federal judge in the child pornography case against Mark Rettenmaier is going to allow defense attorneys to probe the relationship between Best Buy and the FBI at a hearing in Los Angeles starting Wednesday.

“Their relationship is so cozy,” said defense attorney James D. Riddet, “and so extensive that it turns searches by Best Buy into government searches. If they’re going to set up that network between Best Buy supervisors and FBI agents, you run the risk that Best Buy is a branch of the FBI.”

The issue of paid informants has been litigated for decades. Courts generally allow the testimony as long as the payment is disclosed, and defense attorneys can use it to attack the credibility of the informant. In some cases, informants and tipsters can get 25% of money recovered in arrests (up to $250,000), a particularly lucrative incentive in higher-profile drug and customs cases. Paying informants ex post facto isn’t that unusual — although Best Buy insists that its technicians should not receive payment for tipping investigators to crimes of any kind.

However, the court records demonstrate that the FBI did in fact pay some of their techs, and not just after the fact. According to the records that the Washington Post’s Tom Jackman saw, the FBI seems to have carried on a longer-term relationship with a group of technicians, paying them even before tips came in and even before anyone suspected a crime had taken place. That raises the question of whether these technicians had become government agents rather than just informants or good citizens identifying criminals in our midst, as Best Buy suggests. In at least one case, the FBI agent running the informants reported that his source would start finding “CP” after a hiatus of several months.

Prosecutors will argue that, regardless of their arrangement with the FBI, the technicians spotted the files as part of their normal work. The release signed by customers makes it clear too that the technicians will inform on customers when they find the material: “I am on notice that any product containing child pornography will be turned over to the authorities.” That, prosecutors say, waives the Fourth Amendment prohibition on searches without warrants — because in many cases, customers paid for the search expressly to save their hard-drive data. That’s a pretty strong argument, too.

It’s a tricky case, to be sure. What if this was a janitorial firm rather than a computer repair chain, and the FBI paid janitors to look for evidence of corporate malfeasance on the desks of executives? Would that hold up in court — even though the executives paid the janitors to clean their rooms? On the other hand, Best Buy’s customers take their hard drives to the store for the express purpose of salvaging these files, and it’s tough to argue that checking the files out is an extraordinary or intrusive step. In the future, it would be a lot simpler for all concerned if the technicians just acted as good citizens and the FBI kept its money in its pockets, but the court in this case will probably side with prosecutors, especially in light of the release customers sign.

Of course, this doesn’t answer the biggest question of this case: What kind of idiot takes a hard drive with child pornography on it to Best Buy for repair? Answer: The kind of idiots (and worse) who have it in the first place. It’s difficult to argue that justice wasn’t being served in this relationship.