For forensic purposes, the goal in designing an alternative light source for fluorescence viewing is to achieve the greatest contrast between a targeted specimen to be analyzed and the background on which it has been deposited. This article presents an ALS design case study that involved identifying semen stains on white cotton fabric. This case shows how to improve the contrast with which semen stains are seen on white fabric by tailoring both the excitation and emission spectra to the job. The article then describes a new type of ALS that has recently been developed to provide a large and chemical-specific contrast enhancement. It is called Fluorescence Excitation Ratiometry (FER). The author describes how this technology can distinguish different white powders as well as unbleached cotton from bleached wood pulp based papers. Its use to determine whether glass fragments come from the same window is also described. The article concludes with a description of how new ALS designs can enhance fingerprint identification and recording by improving contrast enhancement, as fingerprint ridges are made to stand out with respect to the background on which they have been deposited. 3 figures and 4 references