Soil samples from three different locations
A transfer of animal and plant traces such as leaf fragments, seeds, animal hair, remains of insects or feathers can not be avoided, depending on the course of the crime. Adhesions of soil on shoe soles or vehicle tires can often occur on scenes which are located outdoors. In the course of investigations shoes, pieces of clothing and personal belongings are often seized and examined as evidence.
Recovered trace material is classified and identified on the basis of species-specific morphological-anatomical features, evaluated using analytical methods and compared to samples obtained at the crime scene. Soil samples are examined to determine particle-size and are subjected to simultaneous thermal analysis. In addition, X-ray diffraction and fluorescence analysis are available for the examination of soil-building minerals.
Depending on the purpose of the evaluation, the evidential value of a morphological analysis of plant and animal trace material may be limited, and specific correlation based on morphological characteristics alone is not possible. In a case-based research project carried out at the KTI, plant material was analyzed with the aid of molecular-genetic techniques – analogous to the analysis of human and animal DNA. This led to the first case in which plant material (an oak leaf) recovered from a vehicle driven by a suspect was traced to a specific tree in a wooded area at the scene at which the victim’s body was found.
In the analysis of plant traces, the evaluation of results requires an in-depth knowledge of the natural and cultured propagation techniques of the respective species. Plants which are cultivated by scions are genetically identical and can not be differentiated by DNA-analysis. This knowledge is crucial for the examination of cannabis samples collected from illegal indoor plantations. In such plantations the plants are cultivated with scions on a large scale. The use of DNA-analysis allows the establishment of connections between plantations and seized harvests or allegedly independent plantations. These new possibilities of an individual allocation of plant and animal traces with the means of DNA-analysis will be a major breakthrough for the solving of crimes comparable to the analysis and evaluation of human traces.