Tools such as Hirisplex could be useful in those cases where the perpetrator is completely unknown to the authorities, said Prof Manfred Kayser, who led the study.

BBC: Forensic test can predict hair and eye colour from DNA

Manfred Kayser says ancestry markers can - at best - trace an individual to a broad region: "Human migration history has produced no sharp genetic borders and no sharp appearance borders, " he explains.

BBC: Painting a suspect's portrait with DNA