Blood residue

src: i.ytimg.com

blood residue is the wet and dry blood remnants, and the color changes on the surface where the blood has been shed. In forensic science, blood residues can help investigators identify weapons, reconstruct criminal acts, and link suspects with crime. Analysis of blood residues is also an important technique in archeology.

Video Blood residue

Forensic significance

Blood is about eight percent of a person's weight (usually about five liters), and circulates near the skin surface. Almost all trauma to the body, therefore, results in the shedding of blood. The red color makes it easily visible at the scene, and the residue is very difficult to remove completely. The blood residue has even recovered from the 100,000 year old stone tools.

Laboratory tests can reveal whether a substance is indeed blood, whether the blood is from an animal or a human, and a blood type that belongs to it. This allows researchers to include or exclude people as perpetrators or victims. The antigens that allow blood type testing, however, worsen with age or improper storage. DNA contained in the blood, on the other hand, is less subject to deterioration, and allows an almost exact matching of blood residues to individuals with DNA profiling techniques. Through the analysis of blood stain patterns, information about events can also be obtained from the spatial distribution of blood stains.

Maps Blood residue

Forensic procedures

Finding and documenting blood residue

The newly dried blood stain is a shiny reddish-brown color. Under the influence of sunlight, weather or removal efforts, the colors eventually disappear and the stains turn gray. The surfaces found can also affect the color of the stain.

The crime scenes are usually careful to look for the rest of the blood. A flashlight held at an angle to the surface under examination helps in this, as does a luminol spray that can detect even trace amounts of blood. An alleged test exists by which the blood can be distinguished from other reddish stains, such as soy sauce or rust, found on the scene. The search includes areas outside the scene of the scene where blood may have been removed or bloody fingerprints remain, such as a towel or door knob. In a crime scene outdoors, blood stains can be recovered from the soil or from the surface of the plant.

Standard documentation of blood residues including photos and description of the shape, color, size and position of each stain found. Photos and sketches as a whole are also produced to show the relationship of blood residues to other elements of the scene and to allow pattern analysis. Recently 3D imaging techniques have been tried to document and investigate blood stains.

Collection and preservation

To collect samples for analysis, wet blood was collected with syringe and stored in a tube with anticoagulants, or collected with a dry absorbent cloth. Dry blood is scraped with a knife, or collected with a humidified cotton-tipped applicator, gel lifter or fingerprint tape. Blood-stained clothing and other items are generally wrapped in paper and sent intact to the laboratory. To prevent damage, the sample of blood residue is stored in the refrigerator and, in the case of stains, is dried with air.

src: i.ytimg.com

References

src: www.bloodjournal.org

Further reading

• De Forest, P.R. et al. (2009). Blood on Black: Improved Bloodstains Visualization on Dark Surfaces. Washington, D.C: US ​​Department of Justice.

Source of the article : Wikipedia