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.