The family of a man killed by a drugs overdose administered by an "incompetent" doctor have described a decision not to extradite him to the UK as a "green light for charlatans".
The family of David Gray, 70, of Manea, Cambridgeshire, have been campaigning for Dr Daniel Ubani to face trial in the UK over his death in 2008 but this has been rejected by German authorities who instead chose to prosecute him in his home country.
Today the European Court of Human Rights issued its finding into the family's claim that the German investigation was flawed, saying it had found no violation of human rights.
Speaking on Sky News, Mr Gray's son Rory Gray, said: "German authorities convicted him of a minor misdemeanour, there was no hearing, no trial and Ubani never answered for what he's done.
"This is a green light for charlatans to go to other countries and do whatever they like."
His brother Stuart Gray, of Kidderminster, Worcestershire, said he was "bitterly, bitterly disappointed".
He added: "I think it's got wider ramifications in the UK because it means people can come over from the European Union and not answer to UK law.
"We need to digest this and go back to our lawyers and see if we can lodge an appeal or not."
In 2010 a coroner's inquest in the UK ruled that Mr Gray was unlawfully killed after Dr Ubani, who was working as an out of hours locum, fatally administered 10 times the normal dose of diamorphine.
The disgraced doctor has since refused to return to the UK.
A European arrest warrant was issued by Cambridgeshire Police but could not be carried out because legal proceedings had begun in Germany.
Dr Ubani, a Nigerian-born German citizen, was on his first UK shift as a locum when he killed Mr Gray by injecting 100mg of the drug.
He was struck off in the UK and given a suspended sentence in Germany for death by negligence but is still able to practise there.
In its ruling, the European Court of Human Rights said: "The patient's sons complained that the authorities in Germany, where the doctor was tried and convicted of having caused the death by negligence, had not provided for an effective investigation into their father's death.
"The court accepted that the German trial court had sufficient evidence available to it for the doctor's conviction by penal order without having held a hearing.
"Moreover, the applicants had been sufficiently informed of the proceedings in Germany, and the German authorities had been justified in not extraditing the doctor to the United Kingdom in view of the proceedings before the German courts."
Mr Gray had been suffering renal colic when he was treated by Dr Ubani at his home on February 16, 2008.
His death highlighted national concerns about the standard of locum doctors from abroad working in the UK.
Coroner William Morris described Mr Gray's death as "gross negligence and manslaughter" and said Dr Ubani was "incompetent".
Dr Ubani admitted he had confused the morphine with another drug.
He had flown into the UK the day before his 12-hour Cambridgeshire shift for GP service provider Take Care Now, and had only had a few hours' sleep, a GMC panel was told.
A doctor who gave him an induction expressed concerns that Dr Ubani had no NHS experience, did not know the area, and that he did not have enough time to properly train him.
The doctor had previously not been selected by Leeds Primary Care Trust because he had failed a language test.
However, the GMC panel heard evidence that Dr Ubani was competent in spoken English and his employers had no problems understanding him.