A German man accused of a series of rapes broke down and told a court he was "sorry," as his trial began Monday, DPA reported
The 46-year old locksmith is charged with a total of nine counts of rape or attempted rape.
The man, not named under the German legal system, had previously given a detailed confession under police interrogation, the leading investigator told the court in Dusseldorf.
The court heard that he allegedly broke into ground floor apartments and student accommodation at night, wearing a pair of his wife's tights over his head and armed with a knife.
He approached his victims - who were usually asleep - and threatened them with the knife, the court heard. On several occasions he is said to have fled when the women defended themselves, and on one occasion he ended up in a brawl with a victim's husband, the court heard.
The accused was arrested earlier this year, following a European arrest warrant. The decisive tip-off came from a Belgian police officer.
The man could face up to 15 years in prison. The presiding judge said he may be placed in a psychiatric ward. A verdict is due late October.
Separate from the charges, the court also heard that the man had tricked other women in Germany, the Netherlands and Belgium, over a period of 15 years by pretending to be physically disabled - before asking for sexual favours.
The man asked women if he could use their toilet before asking them to satisfy his sexual desires. He is thought to have tried this ruse, which does not constitute an offence, more than 1,000 times.
On other occasions he tried on trousers in shops and pretended that his pubic hair was caught in the trouser zip, asking shop assistants for help.
The court was told that the man, who himself had literacy difficulties, got a kick out of tricking "intelligent women" into performing sexual deeds out of sympathy