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Crime scenes are normally carefully searched for blood residue. Flashlights held at an angle to the surfaces under examination assist in this, [1] as do luminol sprays which can detect even trace amounts of blood. Presumptive tests exist with which blood can be distinguished from other reddish stains, such as of ketchup or rust, found at the ...
The Kastle–Meyer test is a form of catalytic blood test, one of the two main classes of forensic tests commonly employed by crime labs in the chemical identification of blood. The other class of tests used for this purpose are microcrystal tests, such as the Teichmann crystal test and the Takayama crystal test.
Bloodstain pattern analysis has been used informally for centuries, but the first modern study of blood stains was in 1895. Dr. Eduard Piotrowski of the University of Kraków published a paper titled "On the formation, form, direction, and spreading of blood stains after blunt trauma to the head."
The most publicized test by crime shows is the Luminol process in which a chemical is sprayed onto a surface where blood is suspected to be. [4] The chemical reacts with traces of blood, producing a chemi-luminescence, or apparent glow, as a result of the chemical reaction that occurs.
Rouleaux (singular is rouleau) are stacks or aggregations of red blood cells (RBCs) that form because of the unique discoid shape of the cells in vertebrates. The flat surface of the discoid RBCs gives them a large surface area to make contact with and stick to each other; thus forming a rouleau.
The investigator sprays a solution of luminol and the oxidant. The iron in blood catalyses the luminescence. The amount of catalyst necessary to cause the reaction is very small relative to the amount of luminol, allowing detection of even trace amounts of blood. The blue glow lasts for about 30 seconds per application.
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As drug users are frequently impaired, they can easily fail to notice small traces of blood on these rolled banknotes. [18] This is considered to be of particular concern, as eight out of ten carriers are unaware of their status (as hepatitis can lie dormant for decades), and have little in the way of access to regular healthcare . [ 19 ]