A method of deriving a discrimination feature set for use in identifying biometric spoofs, the method comprising: illuminating each of a plurality of true skin sites under a plurality of distinct optical conditions; receiving first light reflected from each of the true skin sites; deriving true-skin feature values for each of a plurality of features from the received first light to characterize the true skin sites; illuminating each of a plurality of biometric spoofs under the plurality of distinct optical conditions; receiving second light reflected from each of the biometric spoofs; deriving spoof feature values for each of the plurality of features from the received second light to characterize the biometric spoofs; and comparing the derived true-skin feature values with the derived spoof feature values to select a subset of the features to define the discrimination feature set; wherein deriving the true-skin feature values comprises extracting a plurality of true- skin images from the received first light for each of the true skin sites; deriving the spoof feature values comprises extracting a plurality of spoof images from the received second light for each of the biometric spoofs; and each of the true-skin images and each of the spoof images corresponds to an image under one of the plurality of distinct optical conditions; wherein: deriving the true-skin feature values further comprises decomposing each of the true-skin images into a plurality of different spatial frequency components; and deriving the spoof feature values further comprises decomposing each of the spoof images into the plurality of different spatial frequency components; wherein: deriving the true-skin feature values further comprises calculating an intensity distribution for each of the different spatial frequency components for the true-skin images; and deriving the spoof feature values further comprises calculating an intensity distribution for each of the different spatial frequency components for the spoof images; wherein the at least one of the features comprises a ratio of an intensity at a first predetermined percentile of one intensity distribution of the above-mentioned intensity distributions to an intensity at a second predetermined percentile of the intensity distribution. illuminating each of a plurality of true skin sites under a plurality of distinct optical conditions; receiving first light reflected from each of the true skin sites; deriving true-skin feature values for each of a plurality of features from the received first light to characterize the true skin sites; illuminating each of a plurality of biometric spoofs under the plurality of distinct optical conditions; receiving second light reflected from each of the biometric spoofs; deriving spoof feature values for each of the plurality of features from the received second light to characterize the biometric spoofs; and comparing the derived true-skin feature values with the derived spoof feature values to select a subset of the features to define the discrimination feature set; wherein deriving the true-skin feature values comprises extracting a plurality of true- skin images from the received first light for each of the true skin sites; deriving the spoof feature values comprises extracting a plurality of spoof images from the received second light for each of the biometric spoofs; and each of the true-skin images and each of the spoof images corresponds to an image under one of the plurality of distinct optical conditions; wherein: deriving the true-skin feature values further comprises decomposing each of the true-skin images into a plurality of different spatial frequency components; and deriving the spoof feature values further comprises decomposing each of the spoof images into the plurality of different spatial frequency components; wherein: deriving the true-skin feature values further comprises calculating an intensity distribution for each of the different spatial frequency components for the true-skin images; and deriving the spoof feature values further comprises calculating an intensity distribution for each of the different spatial frequency components for the spoof images; wherein the at least one of the features comprises a ratio of an intensity at a first predetermined percentile of one intensity distribution of the above-mentioned intensity distributions to an intensity at a second predetermined percentile of the intensity distribution. deriving the true-skin feature values further comprises decomposing each of the true-skin images into a plurality of different spatial frequency components; and deriving the spoof feature values further comprises decomposing each of the spoof images into the plurality of different spatial frequency components; wherein: deriving the true-skin feature values further comprises calculating an intensity distribution for each of the different spatial frequency components for the true-skin images; and deriving the spoof feature values further comprises calculating an intensity distribution for each of the different spatial frequency components for the spoof images; wherein the at least one of the features comprises a ratio of an intensity at a first predetermined percentile of one intensity distribution of the above-mentioned intensity distributions to an intensity at a second predetermined percentile of the intensity distribution.