A forensic scientist practises classifying fingerprints at the fingerprint department at Punjab Forensic Science Agency in Lahore January 13, 2015. As one of America's top forensic scientists, Mohammad Tahir uncovered evidence that helped jail boxer Mike Tyson for rape, convict serial killer John Wayne Gacy and clear doctor Sam Sheppard of murdering his wife. Then Tahir took on his toughest assignment yet - applying his skills in Pakistan, a poor nation of 180 million people beset by crime and militancy. Picture taken January 13, 2015. REUTERS/Zohra Bensemra (PAKISTAN - Tags: SCIENCE TECHNOLOGY CRIME LAW)