The nucleus of the system is a Spectra Physics Model 171-19, continuous wave, 18-watt argon-ion laser with a Model 270 power supply. The unit has a spectral range of 457.9 to 514.5 nm. Optics permit single and multiline operation in the blue-green portion of the spectrum. The laser head is equipped with an optional fiber interface to permit limited portability of the laser beam, and an optical fiber cable can be used for items too large for the staging area. The laser beam is used to fluoresce certain properties of perspiration, body oils, and foreign substances in latent print residues. Detection occurs when residues absorb the laser light and re-emit it in wavelengths longer than the illuminating source. A comparative evaluation of laser and conventional latent print detection methods found that latent prints were developed in 242 actual criminal cases with fingerprint powders, 930 cases with ninhydrin, 1 case with silver nitrate, 1 case with idodine fumes, and 214 cases with laser. In the laser cases, latent prints were not developed in any instance by subsequent application of fingerprint powder or chemicals. In addition to excitation of latent print residue, the laser has proven valuable in photographing visible, treated and untreated latent prints, producing higher quality products and increasing the latitude of photographic procedures. While the laser system will not replace conventional detection methods, it provides a supplement of value in detecting previously unobtainable latent prints.