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Old 18th November 2020, 06:29 PM   #534
Chris_Halkides
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Originally Posted by JTF View Post
The forensics sweep of Avery's garage and subsequent investigative efforts resulted in the following conclusions.

A portion of the concrete floor reacted to the chemical Luminol. This chemical produces a glowing effect which indicates the presence of human blood, animal blood, some bleaches, and metals. Subsequent testing was unable to produce a definitive source for the Luminol reaction, but analysts were able to determine that the concrete floor had been cleaned with bleach and pain thinner. Brendan Dassey admitted to his mother and investigators that he assisted his uncle in cleaning the garage floor with bleach and paint thinner. Investigators subsequently collected and photographed jeans worn by Dassey.

The front of Dassey's jeans showed signs of apparent bleach splash patterns. Dassey also constructed a drawing of his uncle's garage depicting Halbach, Avery, and Dassey in their locations when Teresa was murdered via gunshot(s) to the head. Two bullet fragments were found in the garage and one of those bullets bores traces of Halbach's DNA. State crime lab firearms expert William Newhouse concluded that this bullet had been fired from a rifle found hanging over Avery’s bed. Newhouse linked ammunition found in Avery's desk drawers to this bullet fragment.
JTF,

As I have explained previously, what you posted is highly misleading. The K-M test is more specific (in the statistical sense of the word) than luminol is, yet it is still only a presumptive test. Even a positive result from a KM test would not demand the conclusion that blood were present; that would require a confirmatory test. Yet the garage gave a negative K-M test. It has been known since at least 1999 that the K-M test can detect blood that has been cleaned with bleach. See attached image, which is a portion of Table 1 from the paper by Gross and coworkers that I previously cited. The first three columns refer to the phenolphthalein test and are B, W, and D, respectively. We do not know what the luminol-positive substance is, but we know what it is not.

If you wish to read up on forensic testing for the presence of blood, I suggest:

Forensic Science Reform Protecting the Innocent Elsevier, 2017. ISBN: 978-0-12-802719-6, Edited by Wendy J. Koen and C. Michael Bowers
Chapter 8: Presumptive and Confirmatory Blood Testing, Christopher Halkides and Kim Lott.
Attached Images
File Type: jpg Gross_phenolphthalein_luminol_concret.jpg (35.0 KB, 1 views)
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Last edited by Chris_Halkides; 18th November 2020 at 06:32 PM.
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