American police investigating the bizarre death of a woman during a domestic row have obtained audio from two Amazon Echo devices.

Silvia Galva, 32, was impaled by a spear-tipped bed post in a struggle with her boyfriend, Adam Reechard Crespo, at their Hallandale Beach home.

Mr Crespo, 43, has pleaded not guilty to second-degree murder. He says her death was a tragic accident.

Police want to establish if the smart-speaker, Alexa, recorded the dispute.

According to the police report, Mr Crespo said he was trying to pull Ms Galvo off their bed during an argument in the bedroom of their Hallandale Beach apartment in July when he heard a snap.

The police report says: "[Mr Crespo] pulled the blade out of the victim's chest 'hoping it was not too bad.'"

But Ms Galva died with a 12in (30cm) double-sided blade through her chest following the altercation at the flat in a seaside city 20 miles (32km) north of Miami, Florida.

A lawyer for Mr Crespo, Christopher O'Toole, told the BBC that Ms Galva's death was unintentional.

Mr Crespo was sleeping when "Silvia came into the bedroom, knocked the door down".

Ms Galva broke off one of the pointy bedposts and "it ended up inside of her", Mr O'Toole said.

Hallandale Police did not return a request for comment.

According to the police report, when Mr Crespo saw Ms Galva had been stabbed he called for a female friend who was in the apartment to call emergency services.

"He tried to save Silvia's life," Mr O'Toole said, "this was the woman he loved."

A police warrant obtained by US media says "audio recordings capturing the attack on victim Silvia Crespo... may be found on the server[s] maintained by or for Amazon.com".

Authorities said Amazon provided multiple recordings, but did not disclose their contents.

Mr O'Toole said he supports the use of the audio in court.

"Ordinarily, I'd be jumping up and down objecting, but we believe the recordings could help us," he said. "If the truth comes out, it could help us."

Mr Crespo was bailed from custody on a $65,000 bond.

Do smart speakers always record conversations?

While smart speakers do always "hear", they do not typically "listen" to conversations.

The major brands record and analyse snippets of audio internally to detect words like "Alexa", "Ok Google" or "Hey Siri", but if those words are not detected, the audio is discarded.

If the wake word is said, however, then the audio is recorded and sent to the voice recognition service at the company.

The big smart speaker companies - Amazon, Apple and Google - all employ staff who listen in to customer voice recordings.

But security researchers have found no evidence that speakers continuously send entire conversations back to a remote server