A method of determining presence of a skinprint uses an apparatus comprising: a primary electromagnetic radiation source; an electromagnetic radiation detector; and a translucent waveguide comprising a first surface providing a waveguide interface coincident with a skinprint receiving region. The method comprises: transmitting primary electromagnetic radiation from the primary electromagnetic radiation source towards the waveguide interface at an angle of incidence relative to and on a first side of a normal line that is perpendicular to the waveguide interface, such that: (a) where the waveguide interface interfaces directly with ambient, the primary electromagnetic radiation incident on the waveguide interface reflects in the waveguide interface at an angle of reflection relative to and on a second side of the normal line opposite the first side; and (b) where a skinprint is present on the skinprint receiving region such that the waveguide interface interfaces with the skinprint and the skinprint interfaces with ambient, at least a portion of the primary electromagnetic radiation incident on the waveguide interface is transmitted through the waveguide interface into the skinprint. The method further comprises using the electromagnetic radiation detector to determine an amount of primary electromagnetic radiation transmitted through the waveguide interface and/or reflected by the waveguide interface. Also disclosed is an apparatus for carrying out the method.
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