Ashton Kutcher is preparing to take to the witness stand to testify against the man charged with the grisly murder of the actor's then-girlfriend.

Michael Thomas Gargiulo stands accused of murdering three women, including Ashton's then-girlfriend, 22-year-old Ashley Ellerin, on February 21, 2001.

And ahead of the trial new court documents have revealed the full horror of the killings.

Ashley, who lived just 400ft away from Gargiulo in Los Angeles, was attacked while she was showering and stabbed 47 times.

Set to testify: Ashton Kutcher, right, pictured with wife Mila Kunis in December last year, will soon appear in court to give evidence about the killing of his then-girlfriend Ashley Ellerin in 2001

Killed: Ashley Ellerin, 22, was a student at the Los Angeles Fashion Institute of Design and Merchandising who had been on dates with and was speaking to Kutcher - who was 23 at the time - the night she was murdered

Happier times: Ashley Ellerin (center) was stabbed 47 times in the shower of her LA apartment

New court documents published in the Radar Online claim: 'He slashed Ms. Ellerin’s throat so violently [he] nearly decapitated her. 'After she was murdered her body was left displayed in a… demeaning pose that was sexual in nature.'

The next victim air conditioning repairman Gargiulo is charged with killing is Maria Bruno, whose home was less than 100ft from Gargiulo’s in Monterey Park, California when she was killed on December 1 2005.

'Gargiulo quite literally butchered her body – stabbing her multiple times, slitting her throat, slicing off her breasts, and staging her for family members and police to find,' state court documents filed by the prosecution.

Alleged victims: Ashley Ellerin, left, Ashton Kutcher's then-girlfriend, was killed in her home in 2001, while Tricia Pacaccio, right, was stabbed in Chicago in 1993

'Butchered': Maria Bruno was killed on December 1 2005 at her home in Monterey Park, California

The prosecutors call Garigulo 'a serial, psycho-sexual thrill killer who engages in the systematic slaughter of beautiful women because he takes sexual pleasure from manipulating, stabbing and killing his victims.'

Gargiulo, now 37, was arrested in 2008 after DNA evidence was recovered from the Santa Monica apartment of Michelle Murphy, who survived an alleged knife attack in April of that year.

He stands accused of her attempted murder.

He is also accused of the 1993 killing of high school classmate Tricia Pacaccio in the Chicago suburb of Glenview, where Gargiulo lived at the time.

Kutcher is due in court to testify in the trial of Gargiulo within the next few months, the report claims.

The 36-year-old actor has rarely spoken about the death of Ellerin - but his written testimony to police reveals shocking details of what he saw on the night of the murder.

On February 21 in 2001, Kutcher had received a call from Ellerin.

The student, aspiring model and part-time Las Vegas stripper had tried to make a date with the then 23-year-old actor - but Kutcher had fatefully turned down the offer.

Standing trial: Michael Thomas Gargiulo stands accused of the grisly murders of three women, and the attempted murder of a fourth

Instead Ellerin and her father spent the day doing some remodeling and painting at her apartment.

After dropping off her father at the airport she called her landlord, Mark Durbin, asking if he could fix her ceiling fan and move some furniture.

Ellerin and Durbin, who had bit parts on Frasier and Six Feet Under, then made love.

Durbin testified in June last year that he and Ellerin were involved in a 'blossoming' relationship.

Ellerin was said to be playing the field, having recently broken up with her boyfriend, an acting coach.

LAPD Detective Tom Small told LA Weekly: ‘She had tons of boyfriends. At that time Kutcher was still coming up.

'He hadn't established his big-time credentials yet. They met through a mutual friend. It was a friendly thing. They went out a couple of times.’

Ellerin had also dated Pitch Black star Vin Diesel and Law And Order's Jeremy Sisto, who reportedly flew her to a set in Toronto, where he was filming 2001's Angel Eyes.

It was a few minutes after Durbin left, that Ellerin called Kutcher to ask him if she should go with him to his friends to watch the Grammys.

He turned her down but said instead he would later visit her at her Hollywood bungalow - just behind the famous Grauman's Chinese Theatre.

Kutcher later told police that he tried to call Ellerin twice during the evening but she did not pick up her phone.

Kutcher drove to her apartment at 10.45pm in the hope of smoothing over what he thought was a looming argument, and found that the lights were on in her apartment and her car was parked outside.

After knocking on the door and calling out to her with no answer, Kutcher said he looked through a window into the apartment and saw what he thought was red wine pooled on the floor.

As he was: Ashton in May 2001, three months after the murder of his then girlfriend

Kutcher, already starring in That 70s Show, thought she was angry at him for not making the earlier date and left.

Unbeknown to Kutcher, Ellerin was lying dead just beyond his view from the window. The red wine he had seen pooled on the floor was her blood.

Ellerin's body was found by her roommate, Justin Peterson.

Kutcher's testimony will be crucial for prosecutors to prove the time of death and strengthen their case.