Laboratory Examination of Blood in Forensic Investigations Blood examination is one of the most important procedures in forensic science because blood can provide valuable biological evidence in criminal investigations. Blood samples and bloodstains recovered from crime scenes, clothing, and other objects may help establish connections between individuals and investigated events. Forensic laboratory analysis involves several techniques designed to detect, identify, characterize, and compare blood samples. One of the initial laboratory procedures is the detection of suspected bloodstains. Visual examination is commonly used to locate stains, followed by preliminary chemical tests known as presumptive tests. The Kastle–Meyer test is a well-known example, in which a pink colour reaction indicates the possible presence of blood. However, presumptive tests are not completely specific, and positive results require further examination. Confirmatory tests are therefore used to provide stronger evidence of the presence of blood. Another important aspect of forensic blood examination is the determination of blood group. The ABO blood group system classifies blood into four main groups: A, B, AB, and O, depending on the presence or absence of specific antigens on the surface of red blood cells. The Rh system, particularly the D antigen, is also important in blood classification. These tests may help compare biological samples and exclude individuals whose blood groups are inconsistent with the evidence. However, blood grouping alone cannot establish the identity of a particular individual. Microscopic and biochemical examinations may also contribute to the characterization of blood samples. Microscopic examination helps assess cellular components, including red blood cells and white blood cells, while biochemical investigations can provide additional information about blood constituents. In forensic investigations, these examinations are selected according to the nature of the sample and the questions that need to be answered. DNA analysis is considered one of the most powerful methods used in forensic blood examination. DNA can be extracted from nucleated cells present in blood samples and analyzed using molecular techniques, particularly Short Tandem Repeat (STR) profiling. The resulting DNA profile can be compared with reference samples obtained from individuals to determine whether the biological evidence is consistent with a particular person. This method has significant value in identifying individuals, excluding innocent persons, and establishing biological associations in criminal cases. Proper handling and preservation of blood evidence are essential for obtaining reliable laboratory results. Samples must be correctly labelled, documented, protected from contamination, and stored under appropriate conditions. Maintaining the chain of custody is also necessary to ensure the integrity and legal reliability of forensic evidence. Any contamination, incorrect labelling, or improper storage may affect the accuracy and interpretation of laboratory findings. Conclusion Laboratory examination of blood plays a fundamental role in forensic investigations. The combination of presumptive and confirmatory tests, blood grouping, biochemical examination, and DNA profiling provides valuable information for the identification and comparison of biological evidence. These methods contribute significantly to criminal investigations and support the presentation of reliable findings in legal proceedings.