Preliminary Considerations. Since blood evidence associated with a crime can provide information that may solve the case, it is essential to correctly document, collect, and preserve this type of evidence. Improperly handled blood evidence can weaken or destroy a potential source of facts in a case.
Why is blood important in a crime scene?
Blood is one of the most important biological traces that are often found on the crime scene. … Proper knowledge enables interpretation of results and makes it possible to get closer to the truth, solve that particular crime and bring the perpetrator to justice.
What are the importance of blood in criminal investigation?
Moreover, the pattern of blood stains can help in reconstruction of a crime scene by conveying information about the relative position and movement of the criminal and victim at the crime scene. At the crime scene, it is important to establish the type, origin, and other characteristics of the blood/blood stain.
How does blood help solve crimes?
The use of blood in forensic analysis is a method for identifying individuals suspected of committing some kinds of crimes. … If antibody proteins detect red blood cells with foreign antigens, they attach to those antigens and cause them to clump.
What is blood evidence?
Blood evidence isn’t just collected off of weapons, but can also be collected off of the floor or other surfaces in a crime scene. This blood is also tested to determine if the blood came from the victim or the suspect. Besides testing, investigators use blood stain patterns to help determine if a crime was committed.
What are the three types of blood evidence?
Bloodstains are classified into three basic types: passive stains, transfer stains and projected or impact stains.
What can Blood tell us at a crime scene?
Thanks to DNA, crime scene blood tests can give a lot of information about victims and assailants. Since blood changes throughout the lifespan of the average human, the researchers guessed that certain hallmarks would shine light on a person’s age. …
What are the two basic types of blood evidence?
There are two different types of blood that can be collected at a crime scene: liquid and dried blood. Liquid blood evidence is generally collected from blood pools but can be collected off of clothing as well, using a gauze pad or a sterile cotton cloth.
What might the shape of blood spots indicate?
As the angle of impact is made smaller or more acute, the bloodstain pattern will become more elongated, elliptical, or oval in shape. The resulting bloodstain’s shape will indicate the direction of travel for that stain and thus, the origin of the drop of blood.
Is blood Class A evidence?
Class evidence consists of substances such as blood and hair, which can be used to place an individual in a general class but cannot be used to identify an individual. For example, blood typing can be used to establish whether someone has A, B, AB, or O blood, but cannot point to a person.
How is blood used as evidence?
The most common applications of blood evidence are: Finding blood with the victim’s genetic markers (ABO blood type, DNA profile, etc.) on the suspect, on something in the suspect’s possession, or something associated with the suspect (such as the suspect’s fingerprints).
Can too much luminol destroy DNA?
Luminol has been widely used in the field of crime scene investigations to detect latent blood; however, luminol has the tendency to destroy DNA evidence. … DNA was extracted from blood-containing denim substrates after fluorescein was applied to the substrates.
Can you tell how old dried blood is?
Non-Destructive Age Testing of Bloodstains
Raman spectroscopy and advanced statistics allow the researchers to date a blood stain accurately, provided said blood stain is less than two years old. Raman spectroscopy involves shining a laser on a sample and measuring the intensity of scattered light.
Is blood direct or circumstantial evidence?
Other examples of circumstantial evidence are fingerprint analysis, blood analysis or DNA analysis of the evidence found at the scene of a crime.
How is dried blood collected?
Dried blood spot specimens are collected by applying a few drops of blood, drawn by lancet from the finger, heel or toe, onto specially manufactured absorbent filter paper. The blood is allowed to thoroughly saturate the paper and is air dried for several hours.