Features of establishing the presence of blood in old stains by the method of thin-layer vertical chromatography

Due to the fact that the bloodstain pattern analysis takes the first place in the structure of the study of biological objects, the question of the study of blood patterns is relevant today. The main task (that will allow to solve the following, which puts the investigation before the experts), is to prove that these patterns, which are examined, contain blood, (regardless of their remoteness, attempts to destroy patterns of blood), find out its types or refute traces of blood. If the expert fails to prove the presence of blood, he must refuse to address the following issues. Otherwise, the expert may obtain results that will ultimately lead him to an erroneous conclusion. The article considers options for extraction of old blood stains in order to establish the presence of blood by the method of thin-layer vertical chromatography. This question is still relevant, as biological material can change under the influence of environmental factors and time and this can be an obstacle to establishing the fact of its presence on physical evidence, and also it can do harm to the quality of the study and the correctness of the conclusions, made as a result of the study. In order to select substances, that could provide rapid extraction of old blood stains, a study was performed using weak solutions of alkalis and acids and subsequent determination of the presence of blood by thin layer vertical chromatography. In immunological studies, there have been cases where blood crusts on non-hygroscopic surfaces under the influence of natural factors (such as high temperatures and direct sun rays) have not been extracted in saline and distilled water for several days. In addition, when using known blood samples in the reactions, the dependence of the saturation of the extracts on the age of the samples and the time of their extraction. These observations prompted researches in the sector of biological research and accounting of the Cherkasy NDEKTs of the Ministry of Internal Affairs on methods for extracting old blood stains, which would allow to detect blood in the shortest possible time by the method of thin-layer vertical chromatography.