What is a Bloodstain? Different Types of Bloodstains at crime scene.

The random distribution of blood in form of drops, splatters, sprays, mists and spurts on the surface or object is called bloodstains. Bloodstains are usually

FORENSIC SCIENCEFORENSIC SEROLOGY

Shubham Kumar

1/29/20246 min read

Bloodstains like drops, pools, wipes, etc, present on the surface or any object in the crime scene, is regarded as one of the most valuable evidence. They serve as the prime evidence that establishes the relations between Suspect, crime scene and victim. Bloodstains are very vital because it is composed of of water, red blood cells, white blood cells, glucose, proteins, hormones and metabolites. Furthermore, these traces holds prominent grounds in uncovering the telltale for the crime committed.

In this article, we are going to get valuable insights on the definition and types of bloodstain patters.

Blood has unique qualities inside and outside the body, affected by factors like age, gender, health conditions, and medications. A specialist can analyze bloodstains at a crime scene, looking for different patterns and combining biology, physics, and math to understand the event.

To understand the bloodstains patterns, first you need to understand, what is blood.

The word blood refers to a highly complex mixture of cells, enzymes, proteins, and inorganic soluble. Blood is composed on Plasma, RBC, WBC and Platelets. Blood is a fluid that makes up approximately 8% of the weight of a human body. Females have approximately 4-5 liters while males have between 5-6 liters.

Blood clots when fibrin traps and enmeshes red blood cells. The clotted material is removed, leaving behind a pale yellowish liquid known as serum.

When blood is outside the body, it doesn't stay liquid for long and can become solid over time (forming clots), except in certain conditions like hemophilia or with the use of blood thinners. The way blood flows depends on the wound—it can drip, spray, flow, or ooze. Blood can also drop or splatter from weapons used, but this happens only outside the body.

Bloodstains | Definition

The random distribution of blood in form of drops, splatters, sprays, mists and spurts on the surface or object is called bloodstains. Bloodstains are usually formed because of dispersal of blood in air, via passive or active forces. In the violent crimes like, murder, assault, grievous hurt, rapes etc, bloodstains hold prominent grounds in establishing the relation between the suspect and crime. Moreover, these stains play a crucial role in forensic investigations as they can provide valuable insights into the dynamics of a crime scene.

Bloodstains usually occurs because of two forces passive and active.

The passive forces, like gravity attracting the blood from an injured body, these bloodstains are only capable to from drops, pools and flows. On the other hand, Active forces are the external forces applied on the blood sources, furthermore, breaking the surface tension of blood. Moreover, active forces encompass wide range of external forces. Therefore, can occur in various patterns, such as impact spatters, spattered patterns, and cast-off patterns, depending on the force and direction of the impact.

Types of Bloodstain Patterns

Primarily the bloodstains are classified into three types, these are Passive, Transfer and Impact/Projected bloodstains.

Passive Bloodstains

The passive bloodstains are the result of gravitational force attracting the blood from the injured body (open Blood Source). Passive force (gravity) mostly became root cause of death by Exsanguination, due to continues attraction of blood. Furthermore, passive force is only capable of forming patterns like drops, pool and flow.

Transfer Bloodstains

When the bloodstains occurs as a result of contact between and blood source and object\surface is called transfer bloodstains. The transfer bloodstains can occur on doors handles, side walls, stairs, buttons, etc. The transfer bloodstains, usually depicts the direction followed by the blood source. Drag marks, cloth patterns, shoe/footprints, handprints, fingerprints, wipes, swipes, doors handles, side walls, stairs, buttons, etc. are some of the common examples of transfer bloodstains.

Active Bloodstains

The active bloodstain patterns are formed when the external force is applied on the blood source, moreover, surpassing the surface tension of blood. Though, there are various types of external forces. Therefore, active blood stains are classified based on the area and force, applied on the blood source. For example, knife, gunshot, bunt weapons, hammer, sword, etc. The active forces are capable of forming patterns like splatters, sprays, mists and spurts. Moreover, these patterns also tends to define the type of weapon used.

Moreover, active forces encompass wide range of external forces. Therefore, can occur in various patterns, such as impact spatters, spattered patterns, and cast-off patterns, depending on the force and direction of the impact.

Impact Bloodstain Pattern

An impact bloodstain pattern is formed when a force is applied to a blood source, overcoming the surface tension of the blood. This results in the random distribution of bloodstains that can vary in shape and size. Impact patterns are typically observed in cases involving gunshots, beatings, and stabbings. The spatters created in impact patterns can vary even if the mechanism causing the spatter is the same, making it challenging for investigators to determine the specific cause solely from the spatter. Therefore, analysts are advised to prioritize examining the size and shape of the spatters before attempting to identify the precise mechanism that caused them.

Gunshot Impact Bloodstain Patterns

These bloodstains are usually of minute diameter approximately 0.1 mm. Gunshots produce mist-like depressions, unique due to their rarity in other scenarios. Back spatter occurs when the projectile enters, while forward spatter results from its exit. Gunshot impact patterns vary based on factors like blood quantity, firearm caliber, projectile velocity, and impact location.

In gunshot there are two sources for the impact blood stain. When the projectile enters into the body, it creates an entry wound, the pattern created at that time is called back spatter. In back spatter blood stain usually occurs on the victim, hands of accused, clothes of accused, and area near the victim. If the projectile exits the body, it will create exit wound, this is called as forward spatter. The blood stains in the forward spatter will is more than the back spatter. However, but forward blood spatter will not be present if the projectile doesn't leave the body.

Stabbing and Beating Impact Bloodstain Patterns

Stabbing and beating typically create bloodstains of 1-3 mm diameter, although variations exist. The culprit may use combined methods to cause similar diameters.

Arterial Bloodstain Patterns

The arterial bloodstain patterns occurs when the arteries or the veins of the blood source (blood), suffers puncture by the sharp object. The arteries carry the blood, which is directly pumped by heart, whereas veins transport the blood back to the heart. The pressure of blood in arteries are more than that of any other part of the body.

Therefore, when it punctures or injury is inflicted on the arteries, the blood gets propelled out, forming the patterns like splash, spray, sprout and large arc like. The bloodstain patterns obtained for arterial injury, leaves its traces on victim, culprit and the area near the attack was inflicted. Furthermore, these bloodstains also indicates whether the attack was inflicted before death or after death. Moreover, giving information about whether the victim was moved from its place or not.

Cast-Off Bloodstain Pattern

The bloodstains formed due to continues application of blunt force on the blood source, is called cast-off bloodstains. These bloodstains are the result of enough force applied to break the blood holding capacity of skin and letting the accumulated blood to flung out, forming bloodstains.

When blunt weapon is used to hit a blood source (body), then on first hit the blood will not immediately accumulates on the impacted area. Therefore, on first hit the blood will not be flung out and no spatter will be formed. The casting off spatter is formed when the blunt force is applied on the same impacted area continuously.

This will result in the accumulation of blood in the impacted area causing injury. The outer layer of the skin holds the blood inside it, the blunt object when attacked produces a centrifugal force. Furthermore, if the centrifugal force of the swinging blunt weapon is more enough to break the blood holding capacity of skin, the blood will fling out. Moreover, resulting in creation of spatter on the victim, attacker and the surface where the incident committed.

These spatters are linear, varying in size and shape. They aid in studying victim and attacker positions and the inflicted force.

Projected Blood Stain Pattern

Projected blood stains occurs when the large amount of blood more than 1 ml, is projected horizontally or downward, exceeding the gravitational pull. The structure of the projected blood stains is spine like projections with fine streaking. The vomiting blood is an example of the projected blood spatter.

This blog contains valuable insights as per the requirements of skills by Forensic Science Laboratories, we aim to provide a collective and informative knowledge to other viewers so that they can understand the bloodstains and types of bloodstains.

Reference

  • "Forensic DNA Typing" by John M. Butler

  • "The Forensic Casebook: The Science of Crime Scene Investigation" by Ngaire E. Genge

  • "Forensic Science: A Very Short Introduction" by Jim Fraser

  • "Practical Crime Scene Processing and Investigation" by Ross M. Gardner