How did the crime happen? Who was the perpetrator? Who is the victim? Investigators collect evidence at the scene. Every little detail can be important. Modern investigation techniques such as DNA analysis and laser and computer tomography are now used to convict perpetrators. And with increasingly sophisticated methods, the police have now taken the hunt for criminals to the next level. New technologies even allow cold cases to be solved. But it has been a long road to get to this point. Great Inventions explores the hunt for criminals yesterday and today.