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Blood Analysis and Its Importance in Criminal Investigations

Forensic investigators routinely recover blood, which is considered one of the most essential pieces of evidence in forensic investigations. Crime scene blood tests can provide a great deal of information about both the victims and the perpetrators, thanks to the use of DNA. 

The examination of the several diverse characteristics of bloodstains can also aid in the elucidation of the circumstances under which some of the most horrific crimes have taken place. Such critical information can help in directing the criminal investigation in the appropriate direction and assisting in the resolution of the crime scene. 

Blood is extremely important in a crime scene investigation, and we will go into greater detail about it in this post.

Forensic experts takes a sample of blood, gun and shells from the crime scene

What is blood evidence? 

Since many people share the same blood type, blood evidence is referred to as class evidence. Class evidence is evidence in a criminal investigation that can be connected to a group of people but not to a particular individual. Moreover, class evidence may be beneficial in weeding out a particular set of suspects. This can also be effective in establishing or falsifying witness testimony.

A crime scene can contain two forms of blood; this can be either liquid blood or dried blood. Both types of blood can be collected and tested. 

Liquid blood evidence is typically gathered from blood pools, but it can also be collected from clothing by using a gauze pad or a sterile cotton cloth to remove it from the garment. On the other hand, the majority of blood collected at crime scenes has already dried. If the deposit is crusty or flaky, it can be scraped off and placed in a paper fold to be saved until needed.

How is blood recovered at a crime scene? 

Blood evidence that is improperly handled can tarnish or destroy a possible source of facts in a case. However, blood evidence that has been appropriately gathered and stored can show a strong link between an individual and a criminal act. An investigation of the pattern of bloodstains can assist police in reconstructing a crime scene by giving essential information about the relative position and movement of a criminal and a victim at the crime scene.

Furthermore, blood evidence can be obtained from weapons and the floor or other surfaces at a crime scene. With a set of clean forceps or a clean cotton swab, investigators can use thread on a bloodstain. They will next roll the thread over the bloodstain to absorb the stain. Overall, blood evidence is frequently retrieved in homicide, assault, and terrorist assaults, including explosions.

High-resolution photography is the most often utilised technique for photographing bloodstains. A scale or ruler is positioned adjacent to the bloodstain to ensure precise measurement, and photographs from all angles are shot. 

What do investigators do with the blood? 

Once the sample has been obtained, it must be kept refrigerated or frozen until it can be sent to the laboratory as soon as practical. First, the sample must be allowed to dry completely at room temperature. It is critical to get the sample to the laboratory as soon as possible because if it is not received within 48 hours, the sample may become ineffective. 

Moreover, there is a direct correlation between the number of professionals responsible for investigating a crime scene and collecting evidence and the type of crime committed and the resources available to the law enforcement agency. The majority of the time, a case will be investigated by a detective who will be responsible for interviewing witnesses and victims. 

When dried blood is discovered on a larger transportable object, an investigator will cover the stained area with paper. The next step will involve taping the paper to the object to prevent contamination. If the object that has been stained is not transportable, there are a variety of methods by which an investigator can obtain a sample.

Additional documenting of all relevant information, including bloodstains on the crime scene, is essential for ensuring that they are correctly interpreted. Even if the crime scene is not accessible, photographing all of the bloodstains in as much detail as possible and adhering to a set of guidelines for photographing bloodstains is critical for the interpretation of the bloodstains.

An employe of a genetic institute prepares a DNA sample in Bogota, Colombia, Thursday, Nov. 14, 2019. The genetic institute through DNA tests was able to verify that two women who were given up for adoption one in Spain and other in Colombia, after the Nevado del Ruiz erupted in 1985, are sisters. (AP Photo/Fernando Vergara)

How important is blood at a crime scene? 

Upon testing and determining that a substance is a blood and that it is human blood, it can be determined if the blood originated from the victim or if it came from the suspect. Additionally, this blood is examined to establish whether or not the blood originated from a victim or from a suspect. 

Blood can determine how a crime was committed. 

Analysts can classify stains based on information gleaned from splatter patterns, transfers, voids, and other signs that aid investigators in reconstructing the sequence of events following bloodshed. Moreover, bloodstain pattern analysis is performed to ascertain the acts or sequence of actions that resulted in the observed bloodstains and patterns. 

Bloodstain pattern analysis can also reveal a variety of information, including the individual’s position at the moment the blood was deposited, the relative positions of individuals at the time of bloodshed, and more. 

Bloodstain analysis can disclose the type of damage and even how the wounds were obtained.

The pattern of the bloodstain, also known as a blood spatter, can aid in identifying the weapon used to inflict the injury and determining whether the victim was moving or immobile at the time of the injury. Furthermore, blood can identify the culprits and participants and prove their involvement in the crime.

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