bloodstain pattern analysis: an aid in reconstruction of

International Medico-Legal Reporter Journal February 2021 ISSN: 2347 - 3525

3 Legal Desire Media & Insights www.legaldesire.com/forensics

Bloodstain Pattern Analysis: An Aid in Reconstruction of the

Crime Scenes Kanika Goel1

ABSTRACT

In forensic science, blood is mostly used for DNA typing. But other information can also be revealed

from the analysis of blood. Bloodstain Pattern Analysis (BPA) is one such aspect of blood that deals

with the study of bloodstains with respect to their shape, location, geometry and distribution patterns.

It helps in determining what may have happened during the incident that led to the bloodshed. It is

considered as a valuable tool for reconstruction of the crime scene. The various mathematical

expressions and principles of fluid dynamics are being employed in the interpretation of bloodstains.

It is an emerging field of forensic science that has become quite common in the past several years. The

present study also ascertains the relationship between I) distance travelled by blood and diameter of

bloodstains produced; II) impact angle and width/length ratio of bloodstains.

Keywords: impact angle, point of origin, fluid dynamics, direction of travel, area of convergence.

INTRODUCTION

According to the Locard’s exchange principle, every contact leaves some traces behind. These traces

or evidence serve as the building blocks in any crime investigation process. Blood is one of the most

commonly encountered physical evidences at the crime scene in cases of homicide, suicide, rape,

burglary, sexual assaults etc.

A brief account of blood and its various components:-

Blood is the connective tissue that circulates throughout our body via the circulatory system. It consists

of two components- plasma and blood cells. Approximately 8% of the total human body weight is

blood. The total blood volume approximately ranges from 4.5 to 6 liters in a normal healthy adult [1].

The two components of blood are-

1. Plasma: It comprises about 55% of the total blood volume [1]. It is the liquid portion of blood.

It consists of approximately 9% of water and contains various dissolved substances such as

electrolytes, proteins, hormones, antigens, antibodies, clotting factors etc [1].

1 M.Sc. Forensic Science, LNJN National Institute of Criminology and Forensic Science, MHA, New Delhi



2. Blood cells: The rest 45% of the total blood volume is composed of blood cells. There are three

types of blood cells-

● Red blood cells (RBCs): They are also called as erythrocytes, and contain a red colored

pigment known as hemoglobin (iron containing protein) [2]. Hemoglobin is responsible

for transportation of oxygen and carbon dioxide. The mature RBCs lack nucleus. The

oxygen rich blood within the arteries is bright red in color due to the formation of oxy-

hemoglobin whereas the blood in veins is oxygen-deficient and is slightly purplish in

color. Also, oxygen can be released from hemoglobin when it comes in direct contact

with the atmosphere. This is the reason why bloodstains progressively become darker

when they are exposed to the environment [1].

● White blood cells (WBCs): They are also known as leukocytes. They contain nucleus

and thus are useful in DNA profiling through blood samples. They play a role in the

defense mechanism and are responsible for immunological responses of the body to

antigens, disease causing microbes or any other foreign particle [1]. They consist of two

kinds of cells- Granulocytes (with granules) and Agranulocytes (without granules).

Granulocytes are of three types- Neutrophils, Basophils and Eosinophils whereas

Agranulocytes are of two types- Monocytes and Lymphocytes.

● Platelets: They are also known as Thrombocytes. They also lack nucleus [2]. They are

responsible for the clotting mechanism of the blood and thereby help in plugging the

leaks in the blood vessels.

Blood is almost found at every crime scene and thus, is an evidence of utmost significance. This

biological evidence can establish the relation between the crime scene and suspect or between the

victim and suspect. The analysis of blood is done for species determination, blood group identification,

characterization of serum genetic markers [1] and DNA profiling that helps in proceeding further in

criminal investigation. The age of dried bloodstains can also be estimated. Furthermore, presence of

various drugs and alcohol can also be confirmed from toxicological analysis of blood.

Another important aspect of blood in forensic science is bloodstain pattern analysis (BPA). It is the

study and analysis of bloodstains with respect to their shape, location, geometry and distribution

patterns [1] in order to gather information about the victim, assailant or suspects and to determine the

sequence of events that have resulted in the formation of such bloodstain patterns. It is an important

tool used in reconstruction of the crime scene.

The following are the objectives of bloodstain pattern interpretation-

● To determine the origin of bloodstains [1].



● To determine the distance between the target surface and the origin of bloodstains [1].

● To determine the angle of impact of bloodstains [3].

● To determine the direction of impact of the blood drops [1].

● To determine the weapon used resulting in bloodstain pattern [1].

● To determine the approximate number of blows, shots etc. hit during the crime [1].

● To determine the type of force behind the pattern of bloodstains [3].

● To determine the relative position of the victim, culprit and other related objects during the

incident of crime [3].

● To confirm the statement given by witnesses and suspects [4].

● To determine the sequence of events that may have occurred during the incident [3].

● To determine the manner of death and differentiate between homicide/ suicide/ accident/

natural death [5].

● Reconstruction of the crime scene [5].

● In some cases, the analysis of bloodstains may also reveal whether the offender was left handed

or right handed [3].

Thus, the analysis of bloodstain patterns can provide us with a lot of information about how the incident

may have occurred and thereby helps in reconstruction of the crime scene.

HISTORY OF BLOODSTAIN PATTERN ANALYSIS

One of the earliest known researches in the field of Bloodstain Pattern interpretation was carried out

by Dr. Edward Piotrowski, assistant at the Institute for Forensic Medicine in Krakow, Poland. In 1895,

his work was documented and published as “Uber Entstehung, Form, Richtung und Ausbreitung der

Blutspuren nach Hiebwunden des Kopfes” [1]. It contains 22 color plates of the bloodstain experiments

conducted by him. This was considered as the most noteworthy research of the nineteenth century [6].

Later, Herbert Leon Mac Donell from Corning, New York translated this work from the German text

to English as “Concerning the Origin, Shape, Direction and Distribution of the Bloodstains Following

Head Wounds Caused by Blows [1].

The forensic chemist in Berlin, Dr. Paul Jeserich examined the homicide crime scenes and worked on

the bloodstain patterns found there [1].

A research on bloodstain trajectories and patterns formed was conducted by the French scientist, Dr.

Victor Balthazard and his associates. In 1939, they presented a paper on their research at the 22nd

Congress of Forensic Medicine- “Étude des Gouttes de Sang Projeté”. Later on, it was translated to

English as “Research on Blood Spatter” [1].



In 1953, Dr. Paul Kirk, University of California, Berkeley published the book “Crime Investigation”

which included a chapter on “Blood: Physical Investigation” in which he discussed the significance of

Bloodstain Pattern Analysis [3]. In 1955, based upon his findings related to bloodstain evidence, Kirk

submitted an affidavit in the court of common pleas in the case of Ohio v. Samuel H. Sheppard. This

was a major breakthrough in the acceptance of bloodstain evidence in court.

Herbert Leon Mac Donell conducted several experiments on bloodstains. In 1971, he got his first

publication entitled “Flight Characteristics and Stain Patterns of Human Blood”. Further in 1973, he

got his second book published- “Laboratory Manual on the Geometric Interpretation of Human

Bloodstain Evidence” [1].

A lot of textbooks, scientific articles and laboratory manuals were published by several scientists and

thus bloodstain pattern analysis started emerging as a new tool in forensic science.

In 1983, IABPA (International Association of Bloodstain Pattern Analysts) was formed by Herbert

Donell [1]. It is an organization of forensic scientists that have expertise in bloodstain pattern analysis.

It currently has hundreds of members from all over the world from scientific and legal backgrounds.

Its main objective is to encourage education and research in the field of bloodstain pattern analysis.

Also, it conducts various training courses in this discipline [7].

In 2002, the Scientific Working Group on Bloodstain Pattern Analysis (SWGSTAIN) was created at a

meeting held by the FBI Laboratory. It comprises bloodstain pattern analysts from North America,

Europe, New Zealand, and Australia. SWGSTAIN is a forum that works for the development of

science of Bloodstain Pattern Analysis [8].

FLUID DYNAMICS AND BLOOD

When blood is exposed to an external environment and it comes in contact with the surfaces, bloodstain

patterns are formed depending upon the various external forces acting upon it [1]. Blood follows laws

of physical sciences and thus behaves according to the principles of fluids in motion [1]. Therefore, it

is necessary to understand the physical properties of blood that are responsible for its behavior when

it is in motion outside the body.

Surface Tension- The cohesive forces known as Van der Waals forces pull the surface molecules

towards the interior of a fluid and reduce the surface area. This phenomenon is known as surface

tension. It also causes the liquid to resist penetration. It is measured in force per unit length (dynes/cm)

[1].

● As a result, blood occupies the least amount of space on the target surface [9].



● When a blood drop falls off an object, it acquires spherical shape, not teardrop shape.

This is due to the property of surface tension. The drop oscillates from spherical to

oval/elliptical shape during flight due to air resistance but surface tension always causes

it to return back to spherical shape until it lands on the surface and collapses [10]. The

larger is the drop, the more is the air resistance and thus it tends to oscillate more than

the smaller droplets [1].

● Due to the surface tension, blood droplets get adhered together and do not break in air.

They can separate and result in spatter formation only when the surface tension of blood

droplets is broken by some means [10]. This can be achieved by 2 ways [9]:

a. When blood strikes another object or target surface.

b. When it is acted upon by some external force.

3.2 Viscosity- It is the property of liquid which is defined as the resistance to flow because of

the mutual forces of attraction present between the molecules. The more viscous is the fluid,

the more slowly it will flow [1]. It is measured in pascal second (Pa s), which is equivalent to

kg m-1 s-1 [4].

● Blood is six times more viscous than water and hence it flows slowly than water. The

viscosity of the blood is due to the presence of high concentration of sialic acid on the

membrane of Red Blood cells. Sialic acid results in the accumulation of large

electronegative charges on the surface of RBCs [1].

● The viscosity of blood increases with time as a result of clotting [1] and decreases with

increasing temperature [11].

3.3 Specific Gravity- The weight of a substance compared with an equal volume of water is

termed as specific gravity. The specific gravity of water is represented as 1.00 and that of blood

is 1.060 [1].

THE CHARACTERISTICS OF BLOODSTAIN PATTERNS

When blood droplets strike some object or surface, the surface tension breaks and results in spattering

of blood. If blood droplets hit a smooth target surface such as tile or glass then it results in very less

spatter and almost smooth edge characteristics of blood droplets are seen. If they hit a rough surface

such as raw wood, then the irregularities present in the surface will break the surface tension of blood

and cause it to spatter, creating satellite spatter and spines [9, 10].

Spines- The small spiny projections extending from parent drop that remain attached to it [10].

Satellite Spatter- The small peripheral droplets that get separated from parent drop and land near it

[10].



Figure 1: Blood droplets hitting the surface at 90 degrees from a height of 30 inches. The target surfaces are A) Smooth

surface, Glass B) Rough surface, Marble (showing spines and satellite spatter) [photographed using android phone-

Samsung galaxyA7 (2018) on July, 18 2020 under artificial light].

Thus, bloodstain patterns vary greatly according to the texture of surfaces on which they fall.

The size of the blood droplet depends on the size of the surface from which it falls. A larger surface

produces a larger blood droplet. Also, the size of the droplet depends upon the height from which it

falls. The longer is the distance travelled, the larger is the diameter [10]. Moreover, the number of spines

and satellite spatter increases with increase in height.

Effect of terminal velocity on free falling drops

When blood falls under the influence of gravity, it accelerates due to the gravitational force acting

upon it. But at some point, the gravitational force will be in equilibrium with the frictional force exerted

by air on the droplet. Hence, the blood drop will no longer accelerate and achieve a stable velocity

known as terminal velocity [10].

The terminal velocity depends on the volume of drop. For a blood drop of volume of 0.05 ml, the

average terminal velocity is 25 ft/sec (approximately). When blood falls from the heights greater than

the height at which terminal velocity is reached, the size or diameter of blood droplets will not increase.

Various studies and researches have revealed that the average sized blood drop achieves its terminal

velocity at a height of 7 feet (approximately) [10].

Directionality of Bloodstains

When the blood droplet falls at an angle of 90 degrees, the bloodstain formed will be circular in shape



[12]. However, when blood droplets strike the surface at an angle of less than 90 degrees, the stains

formed will be elongated or have a teardrop shape. This happens when they are subjected to a force

producing horizontal motion as well as the downward pull of gravity [1].

The acute angle at which the blood strikes the surface is termed as the angle of impact [12]. It can be

calculated using the width to length ratio of blood drops [Determination of impact angle is discussed

later in detail]. The direction of blood drop is established by the stain shape and edge characteristics.

The tapered edge or jagged/distorted edge or exclamation mark always point in the direction of travel

[1].

Figure 2: Determining the direction of travel of blood drop [photographed using android phone- Samsung galaxyA7

(2018) on July, 18 2020 under artificial light].

After leaving the body, the blood tends to clot [clotting can be within 15 minutes]. This property of

blood can help in reconstruction of crime scenes. If at the crime scene, some bloodstain patterns are

found to be more clotted than others, then it can indicate that multiple blows or gunshots may have

occurred over a period of time [12].

DETERMINATION OF IMPACT ANGLE

The angle of impact is the acute angle at which the blood drop strikes the target surface. The free

falling drops hitting the surface at 90 degrees form almost circular bloodstains. But when the impact

angle is reduced than 90 degrees, the shape of bloodstains becomes oval or elliptical and the tail of the

drop indicates the direction of travel.

A mathematical relationship exists between the impact angle of blood drop and the width and length



of the bloodstain produced [1].

Figure 3: The relationship between impact angle and elliptical bloodstain.

As shown in figure 3, the hypotenuse of the right triangle is equal to the length of the bloodstain, the

perpendicular side of the triangle is equal to the width of the bloodstain, and the angle (θ) is the impact

angle [1].

Sin θ = perpendicular/hypotenuse

Sin θ = width/length

θ = Sin-1 (width/length)

Thus impact angle can be calculated using the width and length of bloodstains found at the crime

scene. One must measure them carefully and consider the well-formed bloodstains for measurements

to avoid any error [1].

DETERMINATION OF POINT OF ORIGIN

The point of origin of spatter can be determined from bloodstains. It helps in identifying the positions

of victim and suspect and analyzing whether they were sitting, standing or lying down. Firstly, the area

of convergence is determined to locate the point of origin for a blood spatter. It is a two-dimensional



representation of point of origin on the surface [1]. The area of convergence is determined by tracing

the axis of bloodstains back towards the source or a common point. The point at which these projected

lines converge is known as the area of convergence [1, 9].

Figure 4: Determination of area of convergence.

The area of convergence is two dimensional point of origin. The actual origin of blood spatter lies

above this area in space. Thus, one needs to estimate the height or distance of source of blood from the

area of convergence. For this, the well-formed bloodstains are taken into consideration and impact

angle is calculated for each [using the mathematical expression discussed above]. Now, we have 2

methods for calculating the point of origin:-

Stringing method- At the crime scene, the one end of the string/thread is affixed at the base of

bloodstain and using a protractor, it is elevated at the calculated impact angle and projected to the axis

perpendicular to the plane containing bloodstains, and passing through the area of convergence [1, 9].

This is done for all the bloodstains used. The strings will cluster at some point on the perpendicular

axis. This point is determined as the point of origin of blood spatter [1, 9].

Figure 5 depicts the strings projected to the perpendicular axis to determine the point of origin of

bloodstains.



Figure 5: Stringing method for determining point of origin [photographed using android phone- Samsung galaxyA7, under

natural light on July, 18 2020 under artificial light].

Tangent method- It is based on the trigonometric expression, that is

Tan θ = perpendicular/adjacent

The impact angle of representative bloodstains is calculated. The distance from the base of individual

bloodstains to the area of convergence is calculated and then the point of origin is determined using

the above formula [1, 9].

Figure 6: Formation of right triangle to determine point of origin.

Figure 6 shows the formation of the right triangle and the tangent of the angle of impact. Here, θ =

impact angle, Z = height of point of origin and Y = distance between bloodstain and area of



convergence. Applying the trigonometric expression, we get:

Tan θ = Z/Y

Z = Tan θ *Y

Z (distance of point of origin) = Tan θ*distance between bloodstains and area of convergence

Both methods assume that the blood droplets travel in straight line trajectories. However, they may

travel in parabolic trajectory due to the effect of gravity and air resistance [3]. Thus, while

determining point of origin, a range of possible flight paths and impact sites must be considered that

could produce the same impact angle. This means that the calculated point of origin represents the

maximum height and the actual point of origin may lie below this point or at this point. We may also

get multiple points of origin which indicate the different positions of the victim during the incident

[1].

THE CLASSIFICATION OF BLOODSTAIN PATTERNS

The bloodstains are categorized into three different types- passive stains, transfer stains,

projected/spatter stains [3, 7]. This classification was proposed by Jozef Radziki [3]. The patterns that do

not belong to any of these categories are placed in another category termed as miscellaneous stains [3,

7].

Passive Stains- They are created due to the force of gravity acting alone on the blood [10]. Examples

of passive stains include:

● Free falling drops affected only by gravity.

● Drip Patterns- The patterns formed when liquid blood drips into standing blood or in

the blood pool [3]. These patterns are large and irregular in shape. They consist of small

circular/oval satellite spatters around the boundary of the central stain [1].

● Flow Patterns- They are found on the victim, on walls, or on an object and result due to

the blood flow under the influence of gravity.

● Saturation Stains- They occur when some fabric or clothing comes in contact with blood

pools and results in formation of blood stains on clothes. The location of saturation stain

can indicate towards the position of person [3].

● Blood Pools- Large volumes of standing blood form the blood pool. The blood cells

coagulate and sink because of their weight and transparent liquid (serum) is separated

out, leading to serum separation [5].

● Blood falling while running/walking.



Transfer Stains- They are formed when a wet, bloody surface comes in contact with another surface

and leaves a pattern [4]. Examples of transfer stains include:

● Wipes- When an uncontaminated, clean object is moved through already existing

bloodstain on the surface, then it is known as wipe. The movement is usually considered

as lateral. It helps in sequencing of events [3, 4].

● Swipes- When a bloodstained object is moved over a surface leaving some traces, it is

known as swipe. Here, also the movement is considered as lateral only. It helps in

sequencing of the events [3, 4].

● Contact Patterns- When a bloody object comes in contact with some surface and leaves

an impression of the object due to compression, such as shoe impression, hand print

etc. Contact patterns tell us about the shape and size of the object [4].

Projected/Spatter Stains- They are formed when some other force is also involved in addition to

gravitational force [10]. Examples of projected stains include:

● Arterial Spurting- In arteries, the pressure of flowing blood is more as compared to

veins. When there is a breach in an artery, a large volume of blood escapes out under

pressure resulting in formation of arterial spurts. The pattern usually shows a zigzag or

wave like appearance due to fluctuations in pressure of blood [3].

● Expirated Bloodstain Patterns- When blood is ejected with force from mouth, nose or

respiratory system, it forms spatter. It almost looks similar to impact spatter, but

sometimes air bubbles can be seen in the blood [4, 10].

● Impact Spatters- These stains are formed due to some impact. The impact may be

caused due to some blunt force such as hammer/bat/stick or due to cutting or stabbing

by knife or due to gunshots/explosives. They are usually medium and high velocity

spatters [3].

● Cast-off Patterns- These patterns are created when a bloody weapon/object is swung or

is in some motion. They create a linear pattern, usually seen on ceilings [3, 10].

● Splashes- When a large amount of blood comes in contact with some surface at low

velocity, it results in splashes. They usually have a large middle area with elongated

bloodstains on edges [4].

● Walking/running through exposed blood.

Miscellaneous Stains- The stains/patterns that do not belong to any of the above categories are known

as miscellaneous stains [3, 7]. Examples of miscellaneous stains include:



● Flyspot Patterns- They are small patterns formed due to fly activity that may be

mistaken as some kind of spatter [4].

● Void Patterns- Void patterns are formed when a secondary object is present in between

the blood source and target during blood spatter. The secondary object also receives the

bloodstains due to which the target surface shows a discontinuous pattern of stains

which is known as void pattern. It can indicate that some object may be present during

the incident [4].

● Perimeter/Skeletonized Patterns- When blood drops are distributed before drying out

completely, but they still retain their perimeter, shape and size, then it is known as

skeletonized pattern [4].

● Altered Bloodstains- Addition of foreign material to blood such as water.

Figure 7: Various categories of bloodstains



BLOODSTAIN PATTERNS AND VELOCITY OF FORCE APPLIED

As it is already discussed, when blood is acted upon by some force, surface tension breaks and blood

gets distributed resulting in various patterns. The velocity of force applied is inversely proportional to

the size of bloodstain patterns produced [9]. The smaller force i.e. low-velocity force results in larger

size patterns whereas the greater force i.e. high-velocity force results in smaller size patterns [9]. Thus,

examination of patterns on the basis of velocity can determine the type of force applied and type of

weapon used in the incident [9].

On the basis of velocity of force applied, the bloodstain patterns are classified into 3 categories:-

Low Velocity Impact Bloodstains-

● They result due to gravitational force or due to an external force applied up to the

velocity of 5 feet/second [9].

● The large sized bloodstains are produced having diameter equal to or greater than 3 mm

[9].

● Long, spiny projections may be produced [9].

● Examples of low velocity patterns- free falling blood drops, drip patterns, stepping into

blood, cast-off patterns.

Medium Velocity Impact Bloodstains-

● They result due to the external force applied between 5 feet/second to 25 feet/second

[9].

● The size of bloodstains ranges from 3 to 1 mm [9].

● They may travel up to large distances due to their large size [9].

● Examples of medium velocity patterns- cutting/stabbing trauma, blunt force trauma

(beating with hammer, bat, stick, brick etc.)

● In blunt force trauma, first blow may not produce any pattern. Subsequent hits will

result in formation of spatter [10].



Figure 8: Medium Velocity Patterns- Spatter due to beating with A) Wooden Stick B) Hammer [photographed using

android phone- Samsung galaxyA7 (2018) under natural light on July, 18 2020 under artificial light].

High Velocity Impact Bloodstains-

● They are produced due to the force applied at the velocity greater than 100 feet/second

[9].

● These stains are characterized by misting effect/atomized blood. When blood droplets

are so small in size that it seems to be a fine spray of blood, then it is known as the

misting effect [3]. The size of bloodstains is less than 1 mm in diameter whereas some

larger stains may also be present [1].

● They can travel only small distances i.e. up to 3-4 feet due to their smaller size [9].

● Examples of high velocity patterns- gunshot trauma, explosions, mechanical accidents.

● In gunshot trauma, both forward spatter (due to entrance wound) and back spatter (due

to exit wound) may be produced [9].



Figure 9: High velocity pattern- Forward spatter due to gunshot trauma [photographed using android phone- Samsung

galaxyA7 (2018) under natural light on July, 18 2020 under artificial light].

OBJECTIVE

The objective of the present study is to ascertain the relationship between

I. Distance travelled by blood and diameter of bloodstains produced.

II. Impact angle at which blood falls and size/shape of bloodstains produced.

MATERIALS AND METHODS

The experiments were performed using red ink. A small amount of refined flour was also mixed into

it so that it can mimic the viscosity of blood.

I. For experiment I, blood drops were made to fall on a white chart paper from different

heights- 25 cm, 50 cm, 100 cm, 150 cm, 200 cm, 250 cm. For each height, 2 separate drops

were taken into consideration, their diameters were measured, and average diameter was

calculated and recorded.

II. For experiment II, blood drops were made to fall from a height of 30 inches on the white

chart paper but at different angles- 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50

degrees, 60 degrees, 70 degrees, 80 degrees and 90 degrees. For each angle, 2 separate

drops were taken into consideration, their widths and lengths were measured, and average

width and length were calculated and recorded. The width to length ratio was also

calculated for each angle.



PHOTOGRAPHIC DOCUMENTATION

The photographs of patterns formed were taken using an android phone [Samsung Galaxy A7 (2018)],

with scale.

OBSERVATIONS

I. The greater is the height, the larger is the diameter of the bloodstains formed. Figure 10

shows the variations in bloodstain patterns formed as the height was increased.

Figure 10: Variations in patterns formed when blood was made to fall from different heights.

The diameters of bloodstains produced when blood was made to fall from different heights are

recorded in Table 1.

Table 1: Diameter of bloodstains corresponding to height

Height from which

blood was dropped

(cm)

Diameter of drop 1

(mm)

Diameter of drop 2

(mm)

Average diameter

(mm)

25 13 14 13.5



50 17 17 17

100 18 19 18.5

150 20 21 20.5

200 22 22 22

250 24 24 24

II. The width and length of bloodstains vary due to the angle at which they strike the surface

(impact angle). Figure 11 shows the variations in patterns formed by blood drops when they

hit the surface at different angles.



Figure 11: Variations in patterns formed at different angles.

The width, length and width/length ratio of bloodstains formed at different angles are recorded in Table

2.

Table 2: Width and length of bloodstains formed at different angles



Angle at which

blood was made

to fall on the

surface

Width (mm) Length (mm)

Width/Lengt

h(W/L) Drop 1 Drop 2

Average

Width

(L)

Drop 1 Drop 2

Average

Length

(W)

10º 6 7 6.5 32 33 32.5 0.20

20º 7 8 7.5 30 33 31.5 0.24

30º 10 11 10.5 25 22 23.5 0.44

40º 11 11 11 19 18 18.5 0.59

50º 13 13 13 17 17 17 0.76

60º 13 13 13 15 17 16 0.81

70º 15 14 14.5 15 16 15.5 0.94

80º 15 15 15 15 15.5 15.25 0.98

90º 15 15.5 15.25 15 15 15 1.01

RESULTS AND DISCUSSION

I. Distance travelled by blood and diameter of bloodstains produced.

The diameter of bloodstains increases as the height increases. Also, the number of spines

and satellite spatter increases with increase in height. But one should remember that the

volume of the drop and the surface texture upon which it falls are also some factors that

affect the diameter of bloodstains.

Figure 12 shows the relationship between the height from which blood falls and the

diameter of bloodstains produced on white chart paper.



Figure 12: Graphical representation of diameter of bloodstains versus height from which blood falls.

II. Impact angle at which blood falls and size/shape of bloodstains formed.

The shape of bloodstains varies if blood strikes the surface at different angles. More acute

is the impact angle, more is the length and less is the width of elliptical pattern. At low

angles, such as 10º, 20º, 30º elliptical stains are produced. As the impact angle is increased,

the shape of bloodstain becomes almost circular. At 90 degrees impact angle, circular

bloodstains are produced.

Figure 13 shows the relationship between the impact angle and width/length ratio of

bloodstains produced.

Figure 13: Graphical representation of width/length ratio of bloodstains versus impact angle.



CONCLUSION

Bloodstain patterns found on the crime scene must be examined, photographed, preserved and

evaluated carefully. Bloodstain pattern analysis is an emerging field of forensic science that involves

the study of bloodstains formed when blood is ejected out of the body. It helps in reconstruction of

crime scene and thus aids in proceeding further in criminal investigation. The shape and size of patterns

formed depend on various factors such as the surface on which blood has fallen, distance travelled by

blood, impact angle, weapon used, force applied, volume of blood fallen etc. Hence, knowledge about

bloodstain patterns helps the investigator in analyzing events that may have occurred during the

incident.

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