**4.8. Fingerprint identification**

One of the most common methods used by forensic experts at a crime scene is the identification of fingerprints. The pattern of ridges formed on the tips of human fingers has long been regarded as unique to each individual. In a straightforward IR chemical imaging technique, procedures such as the sample preparation, derivatization or addition of fluorescent antibodies are not required, and fingerprints in a crime scene may be converted to images and made searchable in a database [59]. Williams et al. reported that the latent fingerprints of children may be recovered after extended periods of time have elapsed using Fourier-transform IR microspectroscopy [60]. This technique has been used for adults, and successful results were obtained [25]. King et al. demonstrated that the use of a novel powder that emits fluorescence in the NIR indicated high-contrast fingerprints with excellent ridge detail on polymer bank‐ notes and magazine pages [61].
