In November of 2015, former Georgia police officer Victor Collins was found dead in a backyard hot tub at the Bentonville, Arkansas, home of acquaintance James Andrew Bates. Bates claimed it was an accidental drowning when he contacted police at 9:30am, claiming he had gone to bed and left Collins and another man behind in the tub. But Bentonville Police investigators determined that Collins had died after a fight, while being strangled and held underwater—and that Bates was the only person at the scene at the time. Now investigators have reportedly served a search warrant to Amazon in hopes of getting testimony from a possible witness: the Amazon Echo that was streaming music near the hot tub when they arrived at the scene.

The police were immediately suspicious when they found that the water of the hot tub was tinted red and that Collins had injuries suggesting a struggle—including cuts on an eyelid, a bloodied nose, and swollen lips. There were signs of blood on the sides of the hot tub and on the patio around it and evidence that the tub and the patio had been hosed down to remove the blood. A water meter record from the city’s utility department showed that 140 gallons of water had been used between 1:00am and 3:00am on the night of the incident.

As investigators continued to gather evidence, as first reported by The Information, the Bentonville Police Department requested a search warrant to obtain records from Amazon for anything the Echo might have recorded that night. Police obtained a search warrant for Bates’ Amazon account information on December 4, 2015 and went back to Amazon again in January of 2016 with an extension of the warrant; according to a warrant return affidavit filed by police, Amazon "eventually complied with the warrants on February 8, 2016, but only supplied a portion of what was requested in both search warrants."

Bates was charged with murder in February 2016, but the investigation continued. On June 28, police obtained a separate search warrant for the Echo itself, as well as for Bates' smartphone.

The reason for the search of the Echo is fairly obvious, based on some recent investigations by Ars into the Alexa Voice Service (to be published next week) and a review of Amazon’s prototype Alexa client code. While it’s highly unlikely that Amazon would have retained any data useful to the investigation, some audio may have been retained on the Echo itself. Echo and other devices that use Alexa monitor audio recorded by a microphone for utterances; when speech (or some audio) is detected, it is recorded to a binary audio file and sent in a JSON message back to the Alexa service.

All of Alexa’s voice recognition happens in the cloud, so audio may have been retained briefly by Amazon's servers. But if nothing overwrote the audio buffer files before the device was seized, it would be more likely that the audio files from the night of the incident could be recovered from the Echo itself intact. It may also be possible to forensically recover the audio data if the files were just deleted from the local file system.

In response to a call from Ars, Bentonville Police Department Media Relations Officer Gene Page sent the following statement:

Due to the recent requests for information regarding Case #2015-39460 (James A. Bates, Charge-1st Degree Murder), the Bentonville Police Department announces that it will not be able to address questions prior to the trial. As the investigating agency of the case, the Bentonville Police Department formally directs all inquiries regarding legal issues of this particular case to the Benton County Prosecuting Attorney, Mr. Nathan Smith. Thank you for your continued cooperation and assisting us with providing public information.

Amazon did not respond to requests for details on its response to the case or to questions on how and for how long Echo stores audio. Ars will update this story as more information becomes available. In the meantime, it may behoove you to watch what you say around your Echo.