We consider the application of pulsed THz imaging systems in biomedical diagnostics and mail/packaging inspection. The sub-millimetre spectroscopic measurements obtained from T-ray systems contain a wealth of information about the sample under test. We demonstrate that different types of tissue can be classified based on their terahertz response measured with the chirped probe pulse technique. We demonstrate the performance of a quadratic classifier using linear filter models for feature extraction in the discrimination between different tissues.Modern THz systems are hindered by the slow acquisition speed. The chirped probe pulse technique offers a significant improvement in this context. We present the terahertz responses of biological samples measured using a chirped probe pulse, and discuss the problem of data processing and extracting sample characteristics. q