Understand blood splatters as evidence
If you turn on the television at night, it is very likely that you will find a television program in which investigators are using some type of forensic or scientific method to collect or identify evidence. If you don’t like crime TV shows, you can turn to real TV shows where they analyze a crime scene that has already been solved and the suspect is convicted using forensic evidence collected at the scene.
With over thirty years of police investigation experience and working hundreds of homicide cases, I can assure you today; If you are presenting a case to a jury, you better be able to present some kind of scientific or forensic evidence if you want a conviction.
In this article I will explain some of the basics of blood evidence and how to interpret the clues that blood evidence leaves.
Blood patterns and interpretation of bloodstain patterns are very compelling evidence when used by an investigator who understands, can identify and explain them.
Blood evidence is most often used by law enforcement investigators in criminal cases who have experience and training in blood spatter. However, if a private investigator is helping a defense case with an attorney or working with a family on a wrongful death case and has an understanding and knowledge of blood patterns, they can be just as helpful.
Some of the items that blood evidence can show are movement and momentum during an attack, weapon type, and whether more than one weapon type was used. It will reveal to the trained eye how many times the weapon or weapons were used and the distance between the victim and the attacker.
There are three basic types of blood patterns:
(1) Splashing at low speed.
This occurs with minimal or no force. The blood pattern is much greater than those of medium and high speed.
This is commonly caused by the force of gravity, such as blood falling from a finger or hand.
(2) Medium speed splashing.
This type of blood pattern is usually caused by some form of force or movement. This blood pattern is commonly seen in throbbing-type attacks. The blood is being moved or transported by more than gravity and less than high speed.
A key note to remember with this type of blood spatter is that during any type of blunt force trauma, the first blow or blow does not create any type of blood pattern. It is not until the actual trauma has started to bleed from the wound and a second blow is struck, causing the blood to forcibly scatter or dislodge from the weapon. A good rule of thumb is that the bigger or blunt the weapon, the smaller the drops of blood.
(3) High speed blood splatter.
This type of pattern is produced by a tremendous external force. The simplest way to describe this type of pattern is often called a mist or spray. High speed patterns are commonly created by gunshots, explosives, and injuries caused by heavy machinery are often known to create a high speed pattern.
High speed blood splatter droplets, due to their size, are often invisible to the naked eye. When investigating blood splashes at high speed, it is best to use a high intensity light and / or a magnifying glass to locate and identify evidence of blood due to the size of the blood droplets.
High speed blood splatters can also be used to determine the distance of a subject involved in a shot. When a bullet enters the body, it causes an effect called “recoil.” This is blood blowing in the direction the bullet came from. This fine mist will only travel a distance of two to three feet. You will often find small mist-like droplets (high velocity blood splatters) on the sleeve and occasionally on the chest of the firing subject.
This can be very important when trying to determine or dispute the distance between the shooter and the victim in cases where self-defense is claimed. In some cases to identify the shooter, since many times this evidence of blood is very difficult to see and goes unnoticed. The suspect does not see blood on his clothing and does not wipe it after being involved in the assault or murder. Several reported suicide cases have been turned into homicide cases with this type of evidence after investigators found high-speed blood splatters on the sleeves of informants’ shirts.
Another type of blood evidence is blood transfer. This is blood that has been transported from a source such as hands, hair, and even clothing and then transferred to another object.
When examining evidence of blood, remember that blood will flow downward due to gravity and, being a fluid, it will take the path of least resistance. This will help you identify the position of your victim at the time of the injury and if the victim moved in any way. Often times, a lack of evidence of blood or a “vacuum” indicates that something has blocked blood flow or splashing. Again, this may indicate that the victim was transferred or that an item of evidence is missing from the scene.
An investigator using evidence of blood at the scene can also determine the angle of impact. Measuring the width of the blood drops by their length (minus the tail) to determine the arcsine. This will determine the angle of impact. Once an investigator knows the angle of impact, this can help the investigator determine whether the victim was standing, kneeling, or lying down at the time of the incident. Or even if the attack was moving.
This article is just the beginning and a very basic idea of using blood tests in your research; however, as you can see, only the basics can help you with your case.
