The blood is a biological trace, preserved at the crime scenes involving both humans and animals. The modern interdisciplinary approach of forensics, based on the achievements in the field of medicine, biology, chemistry or physics, makes blood an extremely informative material that allows not only to identify the donor of the material, but also, in many cases, to reconstruct the course of the events. The whole process of securing and analyzing the blood traces is complex and multistage. Management includes activities such as revealing potential bloodstains both by visual inspection and by nonspecific preliminary tests, e.g. using luminol or the Kastle-Mayer test. The samples selected for further analysis are subjected to the specific confirmatory tests, which allow for the group identification of the trace donor. The last stage is the individual identification based on the polymorphic microsatellite sequences and comparison of profiles from samples secured at the scene with the reference material. Blood can also be used as evidence in crimes involving animals, such as poaching, and crime against legally protected species. In solving such cases, molecular methods are also used, consisting in sequencing of species-specific fragments of mitochondrial DNA, followed by bioinformatics analysis, allowing the assignment of the tested material to a specific species. There is no doubt that blood is an extremely important biological material, secured at the sites of the most serious crimes against health and life. Recent decades have significantly expanded the possibility of analyzing blood spots, not only improving the sensitivity of material detection, but also significantly increasing the specificity and the informativeness of analyses, which now allow for reliable individual and species identification of the trace donors.