COPENHAGEN — A Danish inventor’s explanation of how the journalist Kim Wall died on his submarine was further cast into doubt after an autopsy revealed she had been stabbed more than 14 times and the police found video footage of slain women on a hard drive linked to the suspect.

Ms. Wall’s torso — minus her head, arms and legs — was found on a beach on Amager Island near Copenhagen, 11 days after she went to interview the inventor, Peter Madsen, on his self-built submarine in August.

Mr. Madsen, 46, initially gave shifting explanations for the disappearance of Ms. Wall, 30. But he eventually said that she had died onboard the vessel after a hatch unexpectedly collapsed and hit her on the head while she was climbing stairs in the submarine’s tower.

“I didn’t see her die by any deliberate act; I saw her die of something completely different, saw her fall down,” he told the court on Tuesday, according to Politiken, Denmark’s largest daily newspaper.