Shocking interrogation video shows moment husband realized his wife murdered her best friend

It's the stuff of absolute nightmares.

You spend years falling in love and building a life together with someone. Over the time you spend with them, you grow together and your trust deepens. You think you know them - or do you?

For one husband, this nightmare became an awful reality when he made a horrifying discovery about his ex wife.

Zach McArthur was talking to officers about his wife Ashley McArthur after a friend of theirs, Taylor Wright, had been found dead in September 2017.

He was answering questions about his life and finances, including establishing an alibi. Zach may have thought that he was speaking on his own behalf, but little did he know that the officers interrogating him had different ideas.

You see, it turned out that Zach's wife Ashley was in fact the police's primary suspect in the murder case.

Police had a whole line up of suspects, including Taylor's ex-husband, from whom she stole $100,000, her new girlfriend Casandra, and her best friend Ashley.

One day, Ashley had picked Taylor and then stopped by her parent's farm. It was there that she killed Taylor and buried her body.

Ashley, who had previously worked as a crime scene technician, had then stolen her friend's phone and used it to send messages posing as her friend to make it look as though she was still alive.

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She had even responded to frantic messages from Cassandra asking if her girlfriend was okay by saying that she 'needed time to herself'. 'Taylor' had then cancelled dinner plans with her girlfriend, saying she needed a few days to clear her head.

After stealing some $34,000 from her, Ashley shot her friend in the back of the head at her parent's farm, where she buried her using concrete, prosecutors claimed.

Ashley had been helping her friend through an acrimonious divorce. She had been 'holding' money for Taylor in order to conceal her assets throughout the proceedings. But instead of placing it in a safety deposit box, she had actually been putting it into her own account.

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Ashley's husband Zach, who had worked as a private investigator, was interviewed by police during the investigation.

After questioning him about his whereabouts and finances, a recording shows an an officer asking him: "Based on the job we do and the job you used to do, what your thoughts?"

"Feelings aside," the other officer added.

Zach sighs deeply and pauses before answering: "I can't see her doing something like that. She's super intelligent, she's got a masters degree. It's just sloppy, that's sloppy s**t. I can't see her doing that."

Unfortunately, the evidence had stacked up against Ashley, who had been spotted on CCTV at a hardware store purchasing the exact same concrete which had been used to fill in Taylor's grave.

After a four-day trial, a jury found Ashley guilty. She was convicted of first degree murder and was sentenced to life in prison with a minimum sentence of 25 years in custody.