The 18-year-old Turk fired three bullets into her brain and calmly walked away.

Boys at a nearby school, attended mainly by the children of immigrant Muslim families, cheered and applauded when news of the murder reached them.

The so-called “honour killing” of Hatun Surucu, 23, last year shocked Germany and sparked intense debate about a conservative Muslim immigrant community at odds with a secular society.

That anger was rekindled yesterday when Surucu, a minor when the murder took place, was sentenced to nine years and three months by a Berlin court, considered lenient by many Germans.

His brothers, Alpaslan, 25, and Mutlu, 26, were acquitted because of lack of evidence, at which friends and family in the courtroom cheered. The prosecution had sought life sentences for their part in the murder of their sister.

Passing judgment, Michael Degrif said: “It is inconceivable that someone can be killed for living a Western lifestyle.”

Although she was brought up in Germany, Hatun was forced into a marriage with her Turkish cousin in east Anatolia. The marriage broke up and she returned to Berlin with her five-year-old child to live the life of a young German woman: going to discos, renting a small apartment, taking lovers and starting an apprenticeship as an electrician. She abandoned the traditional headscarf and wore fashionable jeans. Her three brothers were upset, as was her father.

The state prosecutor had demanded that all three brothers be convicted. Ayhan, the youngest, had confessed to pulling the trigger but according to the prosecutor the two others had stood guard and obtained the murder weapon. They denied any involvement.

The evidence of a crown witness, a Turkish girl who wore a bullet-proof vest when she stood in the witness stand, was deemed yesterday to be too flimsy for a conviction. Only Ayhan, 19, was jailed after admitting that he wanted to “wipe the stain from our family”.

There are 40 “honour killings” a year in Germany and most of them result from the failure of an arranged marriage, which are illegal in the country.

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