DESI, or desorption electrospray ionization, does in fact exist! A surface with a fingerprint can be sprayed with a solvent and the solvent evaporated directly into a mass spectrometer to be analyzed. However, this does not happen as smoothly as shown in the CSI clip. Once the spray is on the fingerprint, the spray has to be re-evaporated on a hot surface into the instrument, taking about 5 minutes rather than a few seconds. The mass spectrometer analysis would take anywhere from 5 to 15 minutes to provide results, telling only which elements or compound fragments are in the sample, along with their relative ratio to each other. By far the greatest time is spent on re-constructing the molecule and identifying it by cross-referencing with a chemical database. At best, this takes about a week to do, and then we can never be 100% sure of the chemical identification. (We might say that we have a 95% or even 98% confidence limit.) So, it is good science, but to be able to identify the high-energy explosive RDX in 90 seconds definitely happens on a Hollywood time frame!