Renowned expert returns to help fight crime

As one of the top forensic scientists in the United States, 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 nation of 180 million people beset by crime and militancy.

But catching criminals is not Tahir's biggest problem. It's working with the country's criminal justice system.