COPENHAGEN - Sentenced to life in prison for the murder of journalist Kim Wall aboard his homemade submarine in August 2017, Danish inventor Peter Madsen is hoping to get his jail term reduced when his appeals case opens on Wednesday (Sept 5).

The Copenhagen High Court has set aside three days for the hearings on September 5, 12 and 14.

"The appeals case is only about the sentencing. The trial does not deal with questions of guilt," High Court spokesman Karen Hald told AFP.

Madsen appealed against his sentence only, and not the guilty verdict handed down by a Copenhagen district court on April 25 for murdering 30-year-old Wall, chopping up her corpse and throwing her body parts into the sea last year.

The grisly case made headlines worldwide, all the more shocking as it took place in one of the safest countries in the world, according to a report from the independent organisation Institute for Economics & Peace.

On Aug 10, 2017, Ms Wall boarded the submarine with the eccentric and self-taught engineer - a semi-celebrity in Denmark - to interview him for an article she was writing.

Her boyfriend reported her missing when she failed to return home that night. Her dismembered body parts were later found on the seabed, weighted down in plastic bags.

Madsen maintained throughout his trial that her death was accidental.

His lawyer has insisted that his decision to not appeal against the guilty verdict should "certainly not" be interpreted as an admission of guilt.

"He realises that he was found guilty and he has to live with that. He decided not to continue fighting it. He doesn't have the energy needed for that," Ms Betina Hald Engmark told Danish radio DR.

Ms Hald Engmark said the sentence was "disproportionate compared to legal precedent". That will, therefore, be the main issue for the three appeals court judges to consider.

In Denmark, only one other person apart from Madsen has been sentenced to life in prison for having committed a single murder.

"It's unusual to be sentenced to life in prison. What was decisive (for the court) was that it was a crime that was prepared and planned," prosecutor Jakob Buch-Jepsen said when the sentence was handed down in April.

'LOVING PSYCHOPATH'

Madsen changed his version of events several times but ultimately testified that Ms Wall died when the air pressure suddenly dropped and toxic fumes filled his vessel while he was up on deck.

Despite the testimony of many experts, the lack of tangible evidence in the case and the decomposed state of Ms Wall's remains made it impossible to determine an exact cause of death.

An autopsy report concluded she probably died as a result of suffocation or having her throat slit.

Fourteen stab wounds and piercings were also found in and around her genital area.

Madsen had argued that he stabbed her because he wanted to prevent gases from building up inside her torso that would prevent it from sinking to the seabed.

Psychiatric experts who evaluated Madsen - who described himself to friends as "a psychopath, but a loving one" - found him to be "a pathological liar" who poses "a danger to others" and who was likely to be a repeat offender.

A life sentence in Denmark averages around 16 years. Only 25 inmates in Denmark are currently serving life sentences.

After 12 years behind bars, an inmate with a life sentence can ask to be paroled, but the justice system can decide to keep him or her behind bars as long as he or she is considered a danger to society.

The appeals court's verdict is due on Sept 14.