Human error can occur at every stage of toxicological analysis. Another source of error is unforeseeable circumstances that are connected with use of instruments.
Toxicological expert analysis should be considered as the entire process: sampling, delivery to laboratory, storage, toxicological analysis and finally, reporting of results. This paper covers all the main aspects of the preparation of an expert analysis and points out the most important pitfalls that may occur during a procedure using evidence material. In our discussion of the above mentioned areas, we followed the so-called chain of custody.