Amazon's connected personal assistant Alexa may have witnessed a murder. But will she talk?

Investigators in Arkansas recovered the Amazon Echo speaker infused with artificial intelligence from a murder scene, and want to know what Alexa heard, according to lawyers on both sides.

The case centers around Victor Collins, 47, who was found strangled in November 2015 in a bathtub of the Bentonville home of James Bates, who is accused of the crime.

In the investigation, an officer found an Amazon Echo device at Bates's house -- the small cylinder-shaped speaker which responds to voice commands under the name "Alexa."

Prosecutors have obtained a search warrant which would require Amazon to release any relevant data from the device, according to a statement from Benton County prosecutor Nathan Smith.

"It is incumbent on law enforcement officers to examine this data to determine if it has any relevance to the crime," Smith's office said in a statement to AFP.

The case raises questions about privacy and technology at a time when more devices are recording data about users' movements and actions.

It comes after a legal stalemate earlier this year when Apple refused to help unlock a phone used by one of the perpetrators of the attack in San Bernardino, California.

The request, reported by media earlier this week, is believed to be the first time authorities have sought such information from a smart device in a criminal investigation.

Bates's defense attorney Kimberly Weber told AFP that any evidence from the electronic device would likely be "exculpatory" but nonetheless welcomed Amazon's decision.

"We are really applauding Amazon's effort in protecting the privacy concerns of my client," Weber said.

Smith said however the case "is really about seeking justice for the victim" and that the warrant "is the constitutionally authorized means for law enforcement to conduct searches of homes, property or computer devices like the Amazon Echo."

Amazon did not respond to an AFP request for comment.

The US online giant has not released specific sales data but said this week it sold "millions" of the connected speakers over the holiday season.

Some analysts estimate Amazon sold at least five million of the devices from the release in 2014 until the start of the holiday shopping period.

The Echo and similar Amazon devices are designed to be always on, and can respond to commands, such as queries about the weather or news, and can connect to smart appliances in the home.