Blood+Detection+Notes+BB



Blood Detection

o Types of Tests • Crystal • Catalytic • Instrumental Tests o Most aren’t certain, just point to fact that it might be blood o Crystal • Steps • Blood is placed on a microscope slide • Alkaline solution of pyridine is added • Slide is heated • If blood is present crystals form • If positive it is definitely blood • Even 20 year old blood stains can be detected o Catalytic • Depends on breakdown of hydrogen pyroxide • Oxidizing reagents act to produce a visible change in color • Kastle-Meyer Test • Phenolphalein used • Turns pink • Luminol • Sprayed over blood • Glows if it is blood • Hemastix • Blood applied directly • Change color if blood • Good vs Bad • Very sensitive, can detect tiny amounts of blood • If negative, blood is not present • If positive, blood might be present • Not definite o Instrumental • HPLC • High Performance Liquid Chromatography • Absorbs hemoglobin for detection • Determines o Species of origin o Fetal from adult hemoglobin o Estimate of age of blood stain o Visible Stains • Kastle Meyer • Hemastix o Non Visible Stains • Luminol o Other Uses • Often blood prints are half invisible, blood tests can pick up or illuminate the unseen • Can determine whose blood it is • Situation that blood is found in determines way to go about testing it