The Strasbourg court confirmed preventive detention for the man beyond his 10-year jail term. The judges ruled his compulsory confinement was justified as his sadistic disorder posed a threat to society.
The Strasbourg court ruled unanimously Thursday that a Bavarian regional court and Germany's constitutional court had correctly endorsed psychiatric findings that the 28-year-old man be retained in preventive detention.
The man had strangled a woman jogger on a forest path in 1997 at the juvenile age of 19.
By 2008 he had served his 10-year sentence under law applicable to juveniles but has since been kept in preventive detention at Bavaria's high-security Straubing Prison.
The man took his appeals through to Europe's top human rights court, claiming his continued detention breached the European Convention on Human Rights - such as a person's right to liberty and no punishment without law.
From 2013, Germany adopted revised therapeutic detention legislation to allow preventive detention after jail terms for persons who have psychiatric disorders and are considered a risk to society.
Strasbourg and Germany's constitutional court in Karlsruhe had previously declared Germany's post-sentence custodial practices to be partly illegal.
Rights not violated
In its decision Thursday, the seven-member European Court of Human Rights (EuCHR) ruled unanimously that the man's fundamental rights were not violated because the German courts had been "justified" in concluding his mental disorder was such as to "warrant his compulsory confinement."
So-called "retrospective preventive detention" did not breach the principle of "no punishment without law," the judges ruled.
Under German law, convicts who have served their sentence can be held in preventive custody if deemed a threat to society
And, the man's right to speedy court proceedings had not been violated because the relatively complex case had taken time, they added.
They also dismissed a claim that a regional court judge had made a biased remark to the man's woman lawyer.
They did, however, endorse a compensatory payment of 12,500 euros ($13,478) offered by German authorities to the man for being detained in unsuitable accommodation between May of 2011 and June 2013 at Straubing.
From June 20, 2013 onwards Straubing Prison had provided a "suitable therapeutic environment," in a new special center within the prison grounds, although the man had "refused all offers of therapy at that center," the court said.
'High risk' justifies detention
The European judges said a "high risk" remained that the man could commit serious crimes of a violent and sexual nature if released, because he still suffered from a "sexual preference disorder (sexual sadism)."
The 2013 law change allows continued psychiatric detention in facilities separate from prisoners and on the grounds that each case be reviewed regularly.
ipj/rg (AFP, KNA, dpa)