A non-destructive method of analysing a quantity of a skin print, such as a fingerprint, on a reflective substrate 9 comprises using an electromagnetic detector 300 to obtain an optical image of the print and outputting a value for skin print quantity, which is a function of image density of the optical image. A region of interest may be identified within the image corresponding with the deposited print. This region of interest may be processed to distinguish print image data from substrate image data, after which image density may be determined from the print image data. The EM emitter 200 and the detector may be respectively positioned at angles α,β from the normal of the substrate, and the optical image may be derived from EM radiation received at the detector after being reflected off the print and substrate. The skin print quantity may comprise skin print volume. The emitter may be a camera or a white light source comprising a diffuser assembly 250. A chemical analysis of the print may be performed and subsequently stored or transmitted along with a value of print quantity. Image analysis features may guide the interpretation of the chemical analysis results. The optical image may be compared to stored images to confirm donor identity.
