DIRT, BLOOD, AND CLOTHING: REFLECTIVE SPECTROSCOPY INVESTIGATIONS OF HUMAN BLOOD ON GEOLOGIC AND OTHER SUBSTRATES TO SUPPORT FORENSIC INVESTIGATIONS

The intersection of geology and forensic science has grown significantly in several areas of study. One area that is emerging is the use of hyperspectral imaging and reflective spectroscopy to investigate crime scenes both in the context of unmanned air systems and hand held devices. Human blood is a major material that is found in violent crime scenes in both indoor environments and outdoor environments. Indoor environments have extensive geologic materials in the form of minerals such as calcite and titanium oxides used paints, as well as geologic materials such as granite countertops, slate tile and marble. Soils are more likely to be the geologic materials associated with blood in outdoor environments and can be very diverse in nature. Thus indoor and outdoor environments consist of complex mixtures of geologic materials from which human blood needs to be spectrally distinguished. For this investigation reflective spectra of human blood was investigated on clothing and geologic materials and aged over a period of several weeks to determine the nature of variation in spectra. This was done to estimate age relationships. In addition, spectral data from both clothing and geologic substrates that have been covered with substances that can be mistaken for blood, referred to as confuser materials, were investigated to see how close they match human blood. Various different types of clothing and geological samples were collected along with 19 different “confuser” substances that could be mistaken for blood in situations where blood could be involved. Blood has several distinct features and could be observed on several geologic and clothing substrates. Complexities arise, or are expected in distinguishing blood on hematite-rich soils and other red backgrounds with high organic and water content. Results generally show promise for developing age estimations, however the biological or ecological nature of substrates, temperature variation, and intensity of solar lamination, are variables that need to be explored in detail in future work.