The next time you allow a guest into your home for dinner, should you be worried they're secretly video recording every detail of your home for the government? In a new amicus brief filed in the Ninth Circuit Court of Appeals, we've asked the court to reconsider a decision finding that allowing someone into your home means you're also placing yourself at the risk of warrantless home video surveillance.

U.S. Fish and Wildlife agents were investigating Ricky Wahchumwah for the federal crime of selling bald eagle and gold eagle feathers. An undercover agent who went to Wahchumwah's home pretending to be interested in buying feathers was secretly recording all the details of Wahchumwah's home with a small video camera hidden in his clothes. The agent did not obtain a search warrant before recording. After the trial court found no Fourth Amendment violation and refused to suppress the video, Wahchumwah was convicted and eventually appealed to the Ninth Circuit Court of Appeals. We filed an amicus brief in support of Wahchumwah, but a three judge panel of the Ninth Circuit rejected our arguments, finding no Fourth Amendment problems. In our new amicus brief asking the entire Ninth Circuit to rehear the case, we argue the panel made two mistakes.

First, it failed to analyze the home video surveillance under the Fourth Amendment's trespass theory. Last year, the Supreme Court in United States v. Jones made clear that when the government trespasses onto private property for the purpose of obtaining information, it "searches" under the Fourth Amendment. Under common law, a defendant was not liable for trespass if the landowner authorized their entry. But that consent is ineffective if the person is mistaken about the "nature and quality" of the defendant's entry. And here Wahchumwah was clearly mistaken as to the agent's true purpose: to video record everything in his house without Wahchumwah's knowledge. Second, the court incorrectly found Wahchumwah had no reasonable expectation of privacy because he knowingly exposed the interior of his home to the agent when he let him in his house.

Both of these errors really turn on the panel's dangerous misunderstanding of people's privacy expectations. In Hoffa v. United States, the Supreme Court ruled the Fourth Amendment doesn't protect a “a wrongdoer’s misplaced belief that a person to whom he voluntarily confides his wrongdoing will not reveal it.” But at the same time, the Court has always limited searches to ensure they are reasonably related in scope to the circumstances that justify the search in the first place. When an undercover officer enters a home with the permission of the homeowner, he is obviously able to observe things with his eyes, take mental note of them and relay those opinions to other officers when he returns to the police headquarters. This is permissible because people expect visitors to observe portions of their home when they let them in. That's why people typically clean their house and put away embarrassing things before having guests over for dinner.

But people don't expect their guests to look at the letters on their desk, peer into rooms as they walk the hallways and generally rummage at will through the house. But that's precisely what the video camera here has the potential to do. A quick glance into a bedroom may not reveal much to the naked eye, but a video camera can capture it instantly and allow officers to rewind and zoom in from the comforts of their office without the homeowner wondering why their guest is lingering in the hallway. At that point, the surveillance far exceeds the circumstances that justified the search in the first place -- the homeowner's consent -- and renders the search unreasonable and unconstitutional unless the government has a search warrant.

Ultimately, in deciding whether something is exposed to another person, the key question is not whether someone can possibly discover the information but whether another might actually discover it. And with advances in technology, new and unexpected types of intrusions into otherwise private spaces are popping up every day. Obviously, technology like small video cameras should be used by law enforcement to help make us safer. But outside of extreme circumstances involving an imminent physical threat of death or serious violence to another person, law enforcement should be required to obtain judicial authorization through a search warrant before using this potentially invasive technology -- especially when investigating non-violent crimes like the illegal sale of bird feathers.

We hope the entire Ninth Circuit reconsiders it dangerous decision that truly reveals the power of technology to shrink our privacy expectations.