Christina Jacobsen told the Copenhagen district court there was no conclusive evidence to prove the cause of death beyond doubt.
“What we think happened is that the airways were totally or partially cut off. That would be due to either strangulation, throat cutting or drowning,” she said.
However, when asked by Madsen's lawyer Betina Hald Engmark whether Wall's autopsy showed typical signs of strangulation (blood accumulation in the eyes, abrasions on the neck), the coroner replied: “No.”
Madsen, 47, who is charged with premeditated murder, sexual assault, and desecration of a corpse, has changed his version of events multiple times but has maintained her death was accidental.
On the first day of his trial on March 8th, he told the court that Wall, a 30-year-old freelancer, died when the air pressure suddenly dropped and toxic fumes filled his vessel on the night of August 10th, 2017, while he was up on deck.
While the coroner acknowledged that Madsen's explanation of carbon monoxide poisoning “could be” the cause of death, she said “the air seems not to have been able to leave the lungs, which is not the case with lack of oxygen or inhalation of gases.”
An autopsy report on Wall's lungs from October concluded there were “no signs of exhaust gases in the tissue” and Jacobsen said Thursday there were “no signs” of “heat damage to the respiratory system” that Madsen's explanation of toxic fumes would have caused.
She stressed however that Wall's torso had been in the water for a long time and evidence “could have vanished.”
The coroner also testified Thursday about numerous lesions found on Wall's torso and head, with much of the questioning focused on the 14 stab wounds to her genital area.
Presenting sketches to the court, prosecutor Jakob Buch-Jepsen tried to determine whether the stabs — believed to be inflicted with several instruments, including a 50-cm sharpened screwdriver — occurred before, during, or after death.
“The level of blood accumulation indicates that they occurred around the time when there was still blood circulation, or just after. We are probably not talking hours,” she testified.
Madsen testified a day earlier that he had stabbed Wall's body several hours after her death to let out gases that accumulate inside a decomposing body so she would sink to the seabed.
He has previously explained that he dismembered her body because he panicked and wanted her remains off the submarine but couldn't lift her out in one piece.
But the coroner said his explanation didn't add up.
“As the stabs are superficial, gases would not have been able to get in or out,” she said.
Wall's Danish boyfriend, who also testified on Thursday, told the court that she “was afraid to go on the trip in a submarine” but that she was “fascinated by people dedicated to something”.
He reported her missing to police in the early hours of August 11th.
Rescuers who plucked Madsen from the sea around midday on August 11th — after he intentionally sank his sub, according to police – also gave accounts during the third day of the trial on Thursday, as did a former intern at Madsen’s workshop who was with the amateur engineer on August 10th.
Madsen is due to take the stand again on March 28th, with around 35 witnesses to testify in the coming days.
The verdict is due on April 25th. The prosecutor has called for a life sentence, which in Denmark averages around 16 years.