A German police officer is on trial over butchering a Polish businessman he met on a cannibalism fetish website.

Detlev Guenzel, 56, denies murdering Wojciech Stempniewicz, 59, from Hanover, at his home in Gimmlitztal, near Hartmannsdorf-Reichenau, south of Dresden.

Guenzel was arrested after the man's chopped-up body was found in his garden in November, 2013.

The victim's genitals, however, are still missing, according to local media reports.

Prosecutors say he cut the man into pieces before burying him in his garden. His motive was to 'satisfy his sexual lust' but they said there was no evidence the suspect ate any part of his victim.

Defence lawyer Endrik Wilhelm maintained the victim committed suicide by hanging himself. A pathology report indicated he died from apshyxiation.

Guenzel, married to his male partner for 10 years at the time of the alleged killing, was not a murderer, he said.

Guenzel, who has worked for the police for 30 years, and has one daughter, had met Stempniewicz a month earlier at a chatroom on a cannibalism website, which describes itself as "the #1 site for exotic meat", and has more than 3,000 registered members.

After a series of texts and emails they arranged to meet on November 4 at Dresden's main railway station where Guenzel picked him up and then took him to Hartmannsdorf-Reichenau where he ran a bed and breakfast.

According to AFP, a graphic 50-minute video showing the dismemberment of the victim is to be presented during the trial. The footage reportedly shows a man in boxer shorts chopping up a man suspended from a hook, with his mouth taped shut and hands bound behind his back.

Wilhelm said the last scene of the video apparently shows Guenzel exclaiming: "I cannot believe what has just happened!" The lawyer added that while he harboured extreme fantasies, "he couldn't kill someone".

The trial is expected to last until November and will have around 20 witnesses including Guenzel's now estranged life partner. One investigator called the images "pure horror".