The most important category of scientific evidence in arson-related cases is proof of flammable liquid fire accelerants at the scene of the fire, since they are most commonly used by arsonists. A critical step in the analysis of fire debris for the presence and identification of flammables is separation of flammable agents from other fire residue. The selection of separation procedure and the actual technique used determines the amount of accelerant, if any, is eventually recovered. Improper or careless separation could also result in contamination of the suspected residue. The contamination may actually take place even before the separation stage, during transportation of the debris. The method based on the ability of gas chromograph to separate different compounds is most widely used and considered to be scientifically reliable, when performed correctly. However, it has not been adopted by the courts officially as a standard method. Other types of testimony, including fixing of the approximate time of the fire, can also be used in court. However, there is no agreement among the courts concerning admissibility of this evidence, which specifically states the origin of the fire. Since the use of expert and scientific testimony in arson-related cases is often critical to the successful handling of the case, the counsel for both sides should know about the scientific procedures used in the field and be briefed by the expert on the tests carried out for the particular case. A detailed description of the gas chromatography method, several court cases, footnotes, and 71 references are included.