A new DNA test will help police in the UK solve rape cases even when the attacker has not left any traces of sperm, scientists say. The test looks for the genetic hallmark of other cells present in semen, such as skin and immune cells. Its developers at Birmingham's Forensic Science Service say the test will help provide DNA evidence in a further 90 sexual assault cases a year. It was used in a case for the first time in January, New Scientist reports. A suspect was charged and the case is now being heard at court. A common problem for forensic scientists hoping to use DNA fingerprinting to identify assailants in sexual assault cases is that the quantity of male DNA in swabs taken from the woman is often tiny compared with the amount of hers present.