The trial started on Monday of a woman accused of murdering her boyfriend in extraordinary circumstances. 

On a winter night in late 2008 Gabriele P. and Alex H. were having sex at home in their apartment in the east of Munich, the Süddeutsche Zeitung (SZ) reports.

As usual the 28-year-old Alex H. had pulled a pair of diver’s goggles covered in duct tape over his eyes, meaning that he couldn't see.

At some point during the intercourse he asked his girlfriend to tie him down.

But after she had bound him to the bed frame, Gabriele P. reached for an electric saw which was lying nearby. She removed the safety catch and pressed it to her boyfriend's chest. He died from the injuries.

For months his body lay where he had been killed. The 23-year-old trainee teacher cut his head from his body with the saw and then pulled a sheet over the body and never went back into the room, according to the prosecution.

It was only when the young woman took her new boyfriend home six months later, that he discovered the partially dismembered body. But instead of informing the authorities, he enlisted the help of a friend and carried the pieces down into the garden, where they were buried.

Alex H.'s foster parents became worried when they didn't hear from him and employed a private detective to track him down. But they heard a rumour that he had moved to Romania with a new girlfriend and wanted to break off contact with his entire family. It is unclear whether Gabriele P. started the rumour.

An apparent sighting in 2010 also appeared to convince authorities that Alex H. was still alive.

Only in February 2016 did police discover his remains, acting on a tip-off they had received weeks earlier.

it is now up to the judge to decide whether Gabriele P.'s crime constituted murder, or whether there were mitigating circumstances.

According to the SZ, Gabriele P.'s diary records her tumultuous relationship with Alex H. and the demeaning sexual practices he thought up and which she let happen.

Investigators have spoken to witnesses who recount how Gabriele P. threw her boyfriend out of the house after a huge argument at some point in December. But shortly after, he was able to persuade her to let him move back in.

The prosecution alleges though, that it was at this point the young woman decided to murder him.

But her defence saw that the act was not premeditated. It claims that the electric saw lay in the bedroom as the couple were undertaking renovation work.

The attack was an impulsive “act of desperation” – a crime that does not constitute murder – the defence argues.