From the courtroom to the living room (thanks to the hit television series CSI), forensic science is king. Expertise on fingerprints, ballistics and bite mark analysis are routinely called on to solve the most difficult criminal cases — and to put the guilty behind bars. But how reliable is the science behind forensics? A FRONTLINE investigation finds serious flaws in some of the best-known tools of forensic science and wide inconsistencies in how forensic evidence is presented in the courtroom.