DNA at crime scenes was innocent worker's, not phantom killer's, says prosecutor

The German police collected DNA from the scenes of crimes ranging from break-ins to murder. The samples were stored on a DNA database and matches began to appear. One woman's DNA had been collected at all the scenes.

The mystery serial killer was assumed to be behind the strangling of a pensioner in 1993, the shooting of a policewoman in 2007 and four killings in between. Also on the non-existent killer's rap sheet were a restaurant break-in and burglaries.

Police were stumped by the lack of any pattern to the crimes except that they were all committed in south west Germany, France and Austria. They offered a €300,000 reward for information about the supposed killer.

German authorities grew suspicious, though, and conducted tests at suppliers' factories. They found that of 96 swabs that had not yet been used, seven contained the DNA of the supposed mystery killer.

"The puzzle of the phantom killer has been solved," said Volker Link, a German prosecutor on one of the cases, according to Associated Press.

The German Federal Criminal Police Office told AP that it would be investigating what measures could be taken in future to prevent DNA contamination.

DNA evidence is increasingly collected and stored by police forces. In England, DNA evidence can be collected from anyone taken in for questioning by police. It can be kept even if that person is not convicted or even charged with a crime.

Around 4.5 million records are currently on the UK DNA database, and 850,000 of those are said to belong to people who have never been convicted of a crime.

The European Court of Human Rights (ECHR) ruled last year that the retention of innocent people's records is a breach of their human rights as protected by the European Convention on Human Rights.

"The blanket and indiscriminate nature of the powers of retention of the fingerprints, cellular samples and DNA profiles of persons suspected but not convicted of offences, as applied in the case of the present applicants, fails to strike a fair balance between the competing public and private interests and that the respondent State has overstepped any acceptable margin of appreciation in this regard," said the ECHR

"Accordingly, the retention at issue constitutes a disproportionate interference with the applicants' right to respect for private life and cannot be regarded as necessary in a democratic society," it ruled.