Defense attorneys have asked a federal judge to throw out more than 200 hours of conversations FBI agents recorded using hidden microphones planted near the steps of a county courthouse in Silicon Valley.

The lawyers are representing defendants accused of engaging in an illicit real estate bid-rigging and fraud conspiracy. The steps to the San Mateo County courthouse are frequently the scene of public auctions for foreclosed homes. Federal prosecutors have admitted that on at least 31 occasions in 2009 and 2010, FBI agents used concealed microphones to record auction participants as they spoke, often in hushed voices with partners, attorneys, and others. Because the federal agents didn't obtain a court order, the defense attorneys argue the bugging violated Constitutional protections against unreasonable searches and seizures.

In a court brief filed Friday in the case, attorneys wrote:

It bears repeating that this particular public place was immediately outside a courthouse. Defendants’ expectation that discreet conversations outside a courthouse would remain private is surely one that society is prepared to recognize as reasonable. Private affairs are routinely discussed as citizens, their lawyers, and even judges walk to and from court, and lawyers often take clients aside outside the courthouse for privileged conversations. “Common experience” and “everyday expectations” teach that individuals frequently have private conversations near the courthouse despite the public’s access to this location, and expect that such conversations are not subject to the type of dragnet electronic eavesdropping that took place in this case.

A metal sprinkler box, a planter box and nearby vehicles

According to the filing, agents planted eavesdropping devices in at least three locations: a metal sprinkler box attached to a wall near the courthouse entrance, a large planter box to the right of the courthouse entrance, and vehicles parked on the street in front of the courthouse entrance. All three areas are locations where people have a reasonable expectation to have private conversations and where lawyers and clients could reasonably be expected to have privileged conversations, the defense argued.

According to the court filing:

Generally, the recording devices were activated more than an hour before the auctions began, and they would run for a period of time after the auctions had concluded. Some of the devices intercepted every communication that occurred in their vicinity over a period of more than five hours. For example, the Government recorded individuals having private conversations on their cellphones in an area away from the auctions. In one instance, the Government was able to capture an alleged co-conspirator talking on his cell phone with the other party to the call partially audible through the cellphone’s receiver. And the Government repeatedly hid an eavesdropping device immediately adjacent to the spot where one of the bidders usually set up a chair from which he conducted business and communicated with his joint venture partners. These recordings captured far more than just the bids and public pronouncements that were made during the auctions.

The surreptitious recording came in addition to a confidential informant and undercover agent who were regularly on the steps monitoring the auctions. The FBI's decision to covertly record conversations those individuals couldn't hear is tacit admission the intercepted communications were private for purposes of the Fourth Amendment, the brief argued.

It's unclear when US District Judge Charles R. Breyer will rule on the motion. The court challenge was reported earlier by The Recorder.