An apparatus for evaluating genuineness of a sample presented for biometric evaluation, the apparatus comprising: means (121; 323; 621; 710; 823; 1004) for illuminating the sample with light having a plurality of different wavelengths; means (123; 325; 623; 720; 825; 1008) for receiving light scattered from the sample for each of the plurality of distinct optical conditions; means for forming a plurality of images, each such image being formed from the received light for a respective one of the plurality of distinct optical conditions; means for generating a plurality of figures of merit, each such figures of merit being generated from a respective one of the plurality of images; and means for determining whether the generated plurality of figures of merit is consistent with the sample being authentic unconcealed biological tissue; characterised by: each figure of merit C i being determined using the equation: C i ≡ ∑ ξ ∑ η F i ξ η 2 | R low 2 < ξ 2 + η 2 < R high 2 F i 0,0 2. wherein F i ( ξ, η) is a Fourier transform of a corresponding one of the plurality of images f l ( x, y) at a wavelength corresponding to index i, where x and y are spatial coordinates for the corresponding one of the plurality of images, and R low and R high each represent a limit on spatial frequencies of interest; OR each figure of merit C i being determined using the equation: C i = σ i μ i wherein σ i is a moving-window standard deviation and μ i is a moving-window mean, each calculated from a corresponding one of the plurality of images at a wavelength corresponding to index i; OR each a figure of merit C i being determined using the equation: C i = δ i μ i wherein δ i is a moving-window range and μ i is a moving-window mean, each calculated from a corresponding one of the plurality of images at a wavelength corresponding to index i. means (121; 323; 621; 710; 823; 1004) for illuminating the sample with light having a plurality of different wavelengths; means (123; 325; 623; 720; 825; 1008) for receiving light scattered from the sample for each of the plurality of distinct optical conditions; means for forming a plurality of images, each such image being formed from the received light for a respective one of the plurality of distinct optical conditions; means for generating a plurality of figures of merit, each such figures of merit being generated from a respective one of the plurality of images; and means for determining whether the generated plurality of figures of merit is consistent with the sample being authentic unconcealed biological tissue; each figure of merit C i being determined using the equation: C i ≡ ∑ ξ ∑ η F i ξ η 2 | R low 2 < ξ 2 + η 2 < R high 2 F i 0,0 2. wherein F i ( ξ, η) is a Fourier transform of a corresponding one of the plurality of images f l ( x, y) at a wavelength corresponding to index i, where x and y are spatial coordinates for the corresponding one of the plurality of images, and R low and R high each represent a limit on spatial frequencies of interest; OR each figure of merit C i being determined using the equation: C i = σ i μ i wherein σ i is a moving-window standard deviation and μ i is a moving-window mean, each calculated from a corresponding one of the plurality of images at a wavelength corresponding to index i; OR each a figure of merit C i being determined using the equation: C i = δ i μ i wherein δ i is a moving-window range and μ i is a moving-window mean, each calculated from a corresponding one of the plurality of images at a wavelength corresponding to index i.