Wearing army fatigues and a blank expression on his face, Peter Madsen appeared in a Copenhagen district court for a custody hearing over the grisly case that has gripped global audiences.
Journalist Kim Wall, 30, vanished after interviewing Madsen aboard his homemade submarine on August 10. Her headless torso was found floating in waters off Copenhagen on August 21.
Madsen told the court on Tuesday that a 70-kilogramme (154-pound) hatch door fell on her head by accident, killing her instantly and causing her to bleed from the head.
In a panic, he threw her overboard, he said, insisting the body was intact.
"In the shock I was in, it was the right thing to do," Madsen told the court, adding that he had even contemplated taking his own life.
The 46-year-old has been held in custody since August 12 suspected of "negligent manslaughter".
But Danish prosecutors asked the court to extend Madsen's detention, alleging that he murdered Wall and desecrated her body.
Prosecutor Jakob Buch-Jepsen accused Madsen of "having killed Kim Wall in an undetermined fashion, then he dismembered the body, he cut the torso and tied a pipe to it with the intention of sinking it to the seabed."
Madsen admitted Tuesday to desecrating the body by tossing it overboard, but denied having mutilated it.
Madsen's version of events came to light after the judge rejected the prosecution's request that the hearing be held behind closed doors.
The prosecution had argued that an open hearing would jeopardise the investigation.
It also called for Madsen to undergo a psychiatric evaluation.
Authorities are still searching for the rest of Wall's remains, which they hope will provide some clues about the cause of death.
Investigators have not commented on what alleged motive Madsen would have had for killing Wall.
Madsen insisted that there was no sexual relationship between him and Wall, saying their contact had been purely professional.
'Search for clues'
After Wall failed to return home following her interview on August 10, her boyfriend reported her missing on August 11.
That same day, Madsen was rescued from waters between Denmark and Sweden shortly before his submarine sank.
Investigators recovered and searched the vessel, which police believe Madsen sank intentionally.
After scanning the sub to rule out any hidden compartments and to "search for clues to the crime", the police announced nothing new had been found.
Madsen is an eccentric self-taught engineer. In addition to launching his homemade submarine, he has also successfully launched rockets with the aim of developing private space travel.
The Nautilus was the biggest private sub ever made when Madsen built it in 2008 with help from a group of volunteers.
The volunteers were engaged in a long-running dispute over the Nautilus before members of the board decided to transfer the vessel's ownership to Madsen, according to the sub's website.
'Cursed'
In 2015, Madsen sent a text message to two members of the board claiming: "There is a curse on Nautilus".
"That curse is me. There will never be peace on Nautilus as long as I exist," Madsen wrote, according to the volunteers.
Madsen has drawn media interest for his ambitions to pursue amateur space travel?
"My passion is finding ways to travel to worlds beyond the well-known," he wrote on the website of his Rocket Madsen Space Lab.
Danish police are still searching for the clothes Wall wore on the submarine: an orange fleece, a skirt and white sneakers.
Wall worked as a freelance journalist based in New York and China, and her articles were published in The Guardian, The New York Times and others.
A graduate of the Columbia School of Journalism in New York, she had planned to move to Beijing to pursue her career.
Wall had written about the earthquake-hit ruins of Haiti, the macabre torture chambers of Idi Amin's Uganda, and Cubans using hard drives to access foreign culture.
