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Old 12th November 2020, 08:27 PM   #522
JTF
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Join Date: Dec 2012
Posts: 1,493
Originally Posted by Chris_Halkides View Post
Luminol is only a presumptive test, and one that gives a wider range of false positives than other presumptive tests, such as the Kastle-Meyer test. The Kastle-Meyer test gives false positives in the presence of substances that catalyze the same reaction as a peroxidase. Luminol reacts in the presence of catalysts but also in the presence of oxidants. A positive result from a presumptive test indicates the possibility that a substance is present. A positive result is a reason to move on to a confirmatory test. This is (almost literally) Forensic Chemistry 101. McHrozni mentioned some of these problems in the first thread, in comment #3553. Academic references available upon request.

Mr. Ertl agreed under cross examination that the reaction was faint. The claim that it lit up like a Christmas tree is, putting it charitably, an exaggeration, perhaps originating with Mr. Kratz's closing remarks. From what I can gather Mr. Ertl also acknowledged that he tested for blood and that the result was negative. A quick perusal of the trial testimony leaves me with the impression that Mr. Ertl used the phenolphthalein test (the Kastle-Meyer) test. This test is capable of detecting blood that has been diluted by a factor of 1000 or more, although it is still only a presumptive test.
My reference to the Luminol test is in regards to the photographs taken after the chemical was sprayed on the garage floor. If memory serves, 1 of those photographs was included in MAM. It's important to note that Dassey told his mother that he helped his uncle clean the garage and that bleach stains were clearly evident in photographs taken of Dassey's jeans.

Last edited by JTF; 12th November 2020 at 08:34 PM.
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