For years, forensic scientists relied on chemical tests and microscopes to examine evidence gathered at crime scenes. Such techniques often provided inconclusive results or resulted in the destruction or contamination of evidence. By the mid 80s, crime labs throughout the US and abroad began embracing more sophisticated technology, including UV and Fourier transform infrared (FTIR) spectroscopy. Now, scientists can determine the origin of a bomb from only a trace of residue or determine the make and year of a car from a paint chip retrieved at an accident. DNA evidence from a drop of blood the size of a pencil point can rule out a suspect in a sexual assault -- or strengthen a prosecutor's case. Those systems have become major investigative tools at agencies such as the US Postal Service, Federal Bureau of Investigation and the Treasury Department's Bureau of Alcohol Tobacco and Firearms, providing either initial screenings or supplementary data to methods like gas chromatography. In our investigation, Photonics Spectra talked to chief medical examiners, forensic crime lab directors, document examiners and DNA specialists to find out how photonics technology assists them in their jobs and what competing technologies have emerged.