Her dismembered torso was found days later at sea off Copenhagen, and other body parts were found in plastic bags in October.

"We are talking about a cynical and planned sexual assault and brutal murder of a random woman, who in connection with her journalistic work had accepted an offer to go sailing in the defendant's submarine," Burkoe told the court.

In Denmark, life equates to 16 years, which can be extended if necessary.

Immediately after the verdict, Madsen's lawyer, Betina Hald Engmark, told the court she would appeal. The court ordered Madsen kept behind bars during the appeals process.

"I am satisfied that the court has listened to what I said," prosecutor Jakob Buch-Jepsen told reporters outside court.

Throughout the trial Madsen denied murder, saying Wall had died accidentally inside the submarine.

He changed his story several times. Initially he told authorities that he had dropped her off on shore and did not know what had happened to her. He then claimed she had died accidentally when hit in the head by the submarine's hatch. Finally, after her decapitated head was found by police divers in a weighted-down bag along with her appendages and the skull showed no signs of fracture, he said she had been asphyxiated in a malfunction aboard the submarine.

He also initially denied dismembering her, then confessed that he had done so and said he'd thrown her body parts into the Baltic Sea.

Burkoe noted the discrepancies, saying Madsen "failed to give trustworthy explanations." She added that evidence also showed he "has shown interest for killing and maiming of people and has shown interest for impaling."

Madsen listened quietly as the verdict was read, looking down at the desk in front of him.

Prosecutor Buch-Jepsen claimed Wall's murder was sexually motivated and premeditated because Madsen brought along tools he normally didn't take when sailing, including a saw and sharpened screwdrivers.

Madsen's defence lawyer had argued for his acquittal on the charge of murder, saying he should only be sentenced for the lesser charge of cutting Wall's body into pieces.

The cause of death has never been established but the court found that Madsen "cut the body into pieces to hide what had happened."

AP