The Danish inventor accused of murdering journalist Kim Wall during a trip on his private submarine in August goes on trial Thursday in a gruesome case that's attracted global attention.

Peter Madsen, 47, has denied killing 30-year-old Wall on board the vessel, instead claiming she died accidentally on the UC3 Nautilus before he cut her up and "buried her at sea."

In January, prosecutors said in an indictment that Madsen planned the murder by bringing a saw, screwdrivers, strips and pipes, which were used to hit, cut and stab Wall while she was still alive. Her cause of death has not yet officially been determined, but prosecutors said she died by either strangulation or the cutting of her throat.

There are expected to be 37 witnesses during the trial, which is expected to run until April 25, according to The Local newspaper. Madsen's lawyer, Betina Hald Engmark, has not yet disclosed what he intends to say at his trial.

Those who knew Madsen have said in recent interviews the inventor had frequently spoken about dark fantasies.

"He had two sides: He could be a well-spoken and charismatic person who could speak for hours about his submarine. And then ... a much darker side," retired adult movie actress Dorthe Damsgaard, who met him several times, told the Associated Press.

Damsgaard, 48, told the AP she had declined invitations to join Madsen in his submarine because she has claustrophobia.

"He made it no secret to me about having sexual fantasies," Damsgaard said, describing him as "funny, manipulative, serious and scary."

WHO IS PETER MADSEN, THE DANISH INVENTOR CHARGED WITH MURDERING KIM WALL?

An unidentified woman who claims to be Madsen's former sexual partner told WIRED last month details of text messages the two shared that were "still bothering her."

In one exchange in the days before Wall stepped onto Madsen's submarine, the woman asked the inventor to "motivate her with a threat" to help her finish a project she was working on.

“He says he has a murder plan ready in the submarine, and I tell him 'I am not afraid, you have to be more threatening.' He talks about the tools he wants to use, and I say, ‘Oh it’s not threatening,’” the woman told WIRED.

The conversation soon "darkened," and Madsen discussed inviting someone to his homemade submarine, "where they would suddenly change the mood and begin cutting her up," according to the WIRED report.

The woman told the magazine she didn't give the text exchange much thought at the time, but has since turned the texts over to police.

KIM WALL MURDER SUSPECT ALLEGEDLY TEXTED 'MURDER PLAN' ON SUBMARINE TO EX-LOVER

Madsen's wife, who reportedly has sought a divorce, has told investigators that he openly spoke about attending fetish parties without her.

In an interview with Danish weekly Soendagsavisen in 2014, Madsen said he one day "hoped to have a criminal career," adding he didn't want to rob a bank because "no one must be hurt."

Wall grew up in southern Sweden and studied at Paris' Sorbonne University and the London School of Economics before graduating from Columbia University in New York with a master's degree in journalism in 2013. She was last seen alive on Aug. 10, 2017, when she stepped on Madsen's submarine trip in Copenhagen.

After she left to meet Madsen, her boyfriend received several text messages from her. He eventually alerted authorities after the messages stopped coming, who launched a search for the submarine, which didn't have a satellite tracking system.

Authorities believe Madsen sunk his 33-ton submarine on purpose in Køge Bay off Copenhagen, and eventually found Wall's body parts in plastic bags that were weighed down by metal pieces. Investigators have also found videos of women being tortured and killed on his personal computer, though have said that Madsen did not make the video's himself.

Wall's family has declined to comment "for the time being" before the trial, but have raised money since September for the "Kim Wall Memorial Fund Grant" as part of an online crowdfunding campaign from donors around the world. The fund will award a female reporter a $5,000 grant on March 23, which would have been Wall’s 31st birthday.

The Associated Press contributed to this report.