1. A method for determining whether a sensor is coupled to a tissue sample, the sensor being operable to generate a detector signal indicative of absorption of electromagnetic radiation by the tissue sample, the method comprising: generating a plurality of metric values corresponding to the detector signal, each of the metric values guantifying a behavior of the detector signal which is correlated with whether the sensor is coupled to the tissue sample: inputting the plurality of metric values to a neural net, performing data reduction with the neural net based on dependencies among the metric values, and generating a probability value indicative of whether the sensor is coupled to the tissue sample; and determining whether the sensor is coupled to the tissue sample by referring to the probability value.