Methods are described of evaluating the genuineness of a sample presented for biometric evaluation (figure 14). The sample is illuminated under distinct optical conditions (1404). Light scattered from the sample is received (1408). Multiple images are formed, each image being formed from the received light for one of the optical conditions. A set of texture measures is generated, each texture measure being generated from one of the images. It is determined whether the generated texture measures is consistent with the sample being authentic unconcealed biological tissue (1420).