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-the aanalysis of the properties and effects of serum, blood, semen, saliva, sweat, and even fecal matter is called serology -we have ten pints of blood in our bodies -one of the earliest ways to link a suspect to the victim was through the analysis of blood types -Dr. Leon Lattes developed a procedures to apply blood testing to stains on fabric and other materials -the Kastle-Meyer Color test relies on a solution of phenolphthalein and hydrogen peroxide. -around 80% of the members of the human race were found to be secretors which means that the specific types of antigens, proteins, antibodies, and enzymes characteristic of their blood can be found in other bodily fluids and tisues

What happens during the test? -first a piece of absorbent paper treated with starch is wetted down. pressing this over the area where the saliva is located absorbs the enzymes present from the saliva. Iodine is applied with a spray and the paper turns blue as the iodine reacts with the starch, leaving a clearly defined area whereever there's saliva -another test involves moving a powerful light such as a laser across every surface, that can yield traces for visual inspection -the problem with this luminol can destroy some properties of the blood, so its use is limited to proving that blood is present. -another problem is that it reacts to common substances such as bleach and some metals so if these materials are present, there's no point using it even is bleach was used to wipe down blood-splattered areas.