Summary
Highlights
Sergeant Mike McCutchen introduces the video, explaining that he will demonstrate how to collect dried, cleaned, and wet blood evidence. He will also cover proper packaging techniques to avoid cross-contamination and discuss preliminary blood tests using Luminol and Blue Star to find cleaned-up blood at crime scenes. He emphasizes the importance of wearing gloves.
The video outlines essential tools for testing and collecting blood, including sterile or distilled water (individual packaging is preferred), Quick Check blood stain test kits for preliminary field tests, and Hema-Strips, which are also preliminary tests. He notes that Hema-Strips have potential contamination issues and are originally designed for urine analysis.
Sergeant McCutchen demonstrates how to collect wet blood from a surface using a sterile swab. He stresses the critical importance of not packaging wet blood in plastic bags, as this promotes mold growth and DNA degradation. After collection, the swab with wet blood must be air-dried before being placed in a breathable container, such as a paper box. He also highlights the need for a control swab from an unaffected area.
The process of collecting dried blood is shown. For dried blood, a sterile swab is moistened with distilled water and then used to collect the sample. A Quick Check preliminary blood test is then performed on the collected sample, showing a color change to green, indicating a positive result. The Hema-Strip is also demonstrated, showing a similar green color change, but its contamination risks are reiterated.
The preliminary blood test (Quick Check) is applied to a carpet swatch with a stain, demonstrating its effectiveness on porous surfaces. Crucially, the video advises checking the underside of carpets as blood can soak through and be a hidden indicator of a crime scene. This leads into the use of Luminol and Blue Star for detecting blood that has been cleaned up.
Sergeant McCutchen introduces Blue Star and Luminol for detecting bloodstains that have been cleaned. He explains that Blue Star typically comes in two tablets to be mixed with water. He mentions that Blue Star is generally considered to not degrade DNA, unlike Luminol. He demonstrates preparing the Blue Star solution and explains its longer shelf life (around three hours) compared to Luminol.
The video demonstrates preparing Luminol, which is usually a powder mixed with water. While the solutions mix, he shows how to collect thick, dry blood evidence by scraping it onto a 'druggist fold' paper to be sent to the lab. He then transitions to showing the application of Blue Star in a darkened environment on a cleaned wood surface, revealing bright luminescence where blood was present.
Luminol is applied to cleaned metal surfaces (cleaned with water, bleach, and paper towel) in the dark, demonstrating its ability to reveal hidden bloodstains. He emphasizes using a fine mist spray to avoid disturbing patterns. He then sprays a cleaned tile and a carpet square, showing the luminescence of both, noting that Luminol fades quickly, requiring immediate photography with a slow shutter speed and a tripod.
The video concludes by emphasizing proper packaging of blood-stained items, particularly fabric. He illustrates with a shirt having two distinct bloodstain patterns. He warns against folding wet stained fabric onto itself, as this will lead to cross-contamination. Instead, he advises placing paper between different stained areas to preserve the integrity of each sample.
Sergeant McCutchen briefly mentions other chemicals for blood processing, like Luco Crystal Violet or Amino Black, which are usually handled in a laboratory due to safety concerns. He reiterates the importance of taking control samples, extensive photographing, and proper packaging. He provides his contact information and thanks viewers.