IN CIVIL AND CRIMINAL CASES, THE INVESTIGATION OF BLOOD AND OTHER BIOLOGIC FLUIDS CONSTITUTES A MAJOR PART OF SCIENTIFIC EVIDENCE COLLECTION. THE PHYSICAL ATTRIBUTES OF BLOOD SPLASHES ARE A PHENOMENON UNRELATED TO THE CONTENT OF BLOOD AND ARE INTERPRETED APART FROM ITS VISCOSITY AND PHYSICAL CHARACTERISTICS. EXAMINATION OF SPLASHES CAN INDICATE THE DIRECTION AND SOMETIMES THE DISTANCE FROM WHICH THE SPLASH ORIGINATED. ASPECTS OF BLOOD AND BODY FLUID ANALYSIS FALL INTO THREE MAJOR GROUPS INCLUDING EXAMINATION OF BLOOD STAINS TO DETERMINE THEIR ORIGIN; EXAMINATION OF OTHER STAINS SUCH AS SALIVA AND SEMEN TO DETERMINE ORIGIN; AND IMMUNOLOGIC IDENTIFICATION OF INDIVIDUALS TO DETERMINE OR EXCLUDE THEIR IDENTITY. BLOOD STAINS ARE EXAMINED ALMOST EXCLUSIVELY IN THE CRIMINAL FIELD. THEY ARE AN EXAMPLE OF A CONTACT TRACE, WHERE THE CLOSE PROXIMITY OF ONE PERSON TO ANOTHER OR TO AN OBJECT LEAVES SOME OF THE SUBSTANCE IN SITU. BLOOD CONSISTS OF LIQUID PLASMA, RED BLOOD CELLS (ERYTHROCYTES), AND WHITE CELLS (LEUKOCYTES). EACH SPECIES HAS SPECIFIC PROTEIN PATTERNS IN ITS BLOOD, WHICH AID IN DETERMINING HUMAN OR NONHUMAN ORIGIN. THE PRIMARY AIM OF THE FORENSIC EXAMINATION OF BLOOD STAINS IS TO IDENTIFY THE INDIVIDUAL FROM WHOM THE BLOOD ORIGINATED. THIS EXAMINATION INVOLVES STUDY OF THE HIGHLY COMPLEX SYSTEM OF BLOOD GROUPS AND OTHER BIOCHEMICAL CHARACTERISTICS. THE ABO SYSTEM OF CLASSIFICATION REMAINS THE MAJOR FACTOR IN FORENSIC BLOOD GROUP IDENTIFICATION. WITHIN THE BASIC BLOOD GROUPS SUBGROUPS AND OTHER FACTORS, SUCH AS THE RH FACTOR, FURTHER NARROW BLOOD SOURCE IDENTIFICATION. FOR EXAMPLE, CERTAIN FRACTIONS OF PLASMA PROTEINS, HAPTOGLOBINS, ARE USED IN PATERNITY TESTING. ALTHOUGH PATERNITY CANNOT BE CONCLUSIVELY PROVEN BY THESE METHODS, IT IS POSSIBLE TO EXCLUDE INDIVIDUALS BASED ON BLOOD ANALYSIS.