The child pornography case against a California doctor whose computer was searched after he submitted it to Best Buy’s Geek Squad for repair has been dismissed after a judge ruled that an FBI agent made “several false or misleading statements or omissions . . . with reckless disregard for the truth” in a search warrant affidavit.

The case against oncologist Mark Rettenmaier attracted national attention because it revealed that technicians at the Geek Squad’s central repair facility in Kentucky had been paid by the FBI and would tip off the FBI field office in Louisville when they spotted possible child pornography on computers. Computers taken to Best Buy stores around the country for repair are all shipped to the Kentucky facility.

In May, the Electronic Frontier Foundation filed a lawsuit against the Justice Department seeking records “concerning the FBI’s relationship with Best Buy and other computer repair facilities.” The privacy group first filed a Freedom of Information Act request with the FBI in February, after The Washington Post reported the link between Best Buy and the FBI, but the FBI declined to disclose the information.

Best Buy said that its technicians do not search customers’ computers seeking illicit material but that when they happen to see it while doing repair, they are obligated to report it. They do so about 100 times a year, a Best Buy spokesman said.

A Geek Squad agent fixes a computer at the group’s Kentucky headquarters. (Ken James/Bloomberg News)

“Geek Squad does not work for the FBI and never has,” the company said in a statement in May.

When Rettenmaier took his HP Pavilion desktop to the Best Buy in Mission Viejo, Calif., in 2011, he consented to have it searched while being repaired to recover any lost photos. No warrant is needed for such a search.

But Rettenmaier’s attorney, James D. Riddet, discovered that the FBI made payments to some of the technicians who tipped them off to pornography, often about $500, and considered them “confidential human sources” in internal records.

Riddet raised the issue of whether that made the Geek Squad employees de facto FBI employees — and therefore government agents who would need a search warrant.

On Rettenmaier’s computer, a technician found one photo of a naked girl, believed to be 9 years old, in the “unallocated space” on Rettenmaier’s hard drive. It did not show the girl’s genitalia or any sex act.

Unallocated space is where deleted data resides on a computer until it is overwritten by other data. But it often does not have metadata, such as when it was created, accessed or deleted, and because it lacks that information, courts have ruled that photos found in unallocated space cannot be proved to be “possessed” by the computer’s owner without other evidence.

Riddet argued that when the Geek Squad delved into the unallocated space, it was searching beyond standard data recovery to try to help the FBI. But U.S. District Judge Cormac J. Carney rejected that argument. The Geek Squad technician testified that he was simply trying to recover all the customer’s photos, wherever they were.

The judge noted that Best Buy warns customers that it will notify the authorities if illicit material is found. He said “Rettenmaier’s expectation of privacy” after he gave the computer to Best Buy “and repeatedly consented to data recovery services is not one that society is prepared to recognize as legitimate or reasonable.”

But the FBI used the discovery of that photo to obtain a search warrant for Rettenmaier’s home and other computers. When Rettenmaier returned home, his iPhone was seized. On it were hundreds of pornographic photos, federal prosecutors said.

Carney said that search was illegal because it wouldn’t have been authorized if FBI agents had accurately described what was originally found on Rettenmaier’s computer in Kentucky. Special Agent Cynthia Kayle “falsely stated in the affidavit” for the search warrant “that the [child] image was child pornography,” Carney said in a May hearing in federal court in Santa Ana, Calif. “It was child erotica, the possession and viewing of which is not unlawful.”

The judge noted that Kayle also failed to state that the image was found in the unallocated space of Rettenmaier’s computer and that three separate searches of the hard drive were done to find the image. “This one image of child erotica,” Carney said, “is simply not sufficient to search Dr. Rettenmaier’s entire home, the place where the protective force of the Fourth Amendment is the most powerful.”

The judge then suppressed all the evidence seized from Rettenmaier’s house, including the photos on his phone.

Federal prosecutors initially filed a notice of appeal. But they missed a deadline to file their first brief and on Monday filed a motion saying that “having evaluated the evidence remaining after the Court’s ruling on defendant’s suppression motions, the government believes it is in the interest of justice to dismiss the case.”

Carney then dismissed the case.

“I think what this means,” Riddet said, “is the FBI needs to be much more careful about representations they make in search warrant affidavits and make sure they advise judges what the facts are. If they had done that in this case, I don’t think the search warrant would have been issued.”