Prostitution has long been legal in Germany, and the country has been called "Europe's biggest brothel". Even in the 1800s, police preferred a system of regulation so they could supervise prostitution, according to the book Prostitution by Eva-Maria Heberer.

But forced prostitution continues to be an issue as well. Under King Friedrich Wilhelm IV, brothels were banned in large parts of Prussia for some years, and prostitutes had to be registered.

This was so traumatic, he said, that it made him recall seeing his father rape his mother when he was six years old.

Grotheer then saw "the eyes of Jesus" and stabbed the woman, his lawyer said."He is more or less trying to put all the blame on the victim," prosecution lawyer Michael Schieffers said.

Christian Grotheer, 27, from Hamburg got to know around 300 people on internet chat rooms, most of them women, his lawyer Burkhard Benecken said, reading from a statement from the defendant on the first day of his trial.

He used the online nicknames "Rosenboy" or "Riddick300" on the chat rooms, the latter after a fictional serial killer in the gory 2000 science-fiction movie Pitch Black with Vin Diesel, daily Die Welt said.

Grotheer then followed her, armed with a kitchen life, knocking her over by a field and stabbing her 12 times in the back and 14 times in the chest.

Her body was discovered the next day by a passer-by, Spiegel said. He claims that, after consensual sex, the mother-of-three had demanded money and had threatened to go to the police and accuse him of rape.

The general requirements for these permits are that you have adequate German skills, can support yourself financially, have health insurance and have no criminal record.

You can apply for what’s called permanent EC residence after living in Germany for five years under some form of limited residence permit (ie a work permit).

The Nazi regime implemented restrictions on prostitutes, and many cities banned the practice in public places.

But prostitutes were also used by Adolf Hitler’s government to try to boost the performance of soldiers, as well as to reward prisoners at concentration camps - a manipulative method of creating competition and division.

And EU Blue Card holders (people with a gross income over €49,600, or €38,688 depending on the profession) can get permanent residence after working 33 months, or just 21 months with a B1 language certificate.