BLOODSTAIN PATTERN ANALYSIS TUTORIAL

The success or failure of any criminal investigation often depends on recognizing the physical evidence left at a
crime scene and the proper analysis of that evidence. Crime scenes that involve bloodshed often contain a wealth of
information in the form of bloodstains.  
The pattern, size, shape, and the location of such stains may be very useful in
the reconstruction of the events that occurred.

Bloodstain Pattern Analysis:
is the examination of the shapes, locations, and distribution patterns of bloodstains,
in order to provide an interpretation based on where the patterns were found. Also, the study is based on the premise
that all bloodstains and bloodstain patterns are characteristic of the forces that have created them.

The determinations made from bloodstain patterns at the scene can be used to:
Confirm or disprove assumptions concerning events and their sequence:
Position of victim. (standing, sitting, lying)           Evidence of a struggle. (blood smears, blood trails)

Confirm or disprove statements made by principals in the case:
Are stain patterns on a suspects clothing consistent with his reported actions?    
Are stain patterns on a victim or at a scene consistent with accounts given by witnesses or the suspect?

Blood Volume
On average, accounts for  8 % of total body weight 5 to 6 liters of blood for males 4 to 5 liters of blood for females.
A 40 percent blood volume loss, internally or/and externally, is required to produce irreversible shock (death).
A blood loss of 1.5 liters, internally or externally, is required to cause incapacitation.

Surface Tension (Remember this from elementary school?)
The elastic like property of the surface of blood makes it tend to contract, caused by the forces of attraction
between the molecules of the liquid.The cohesive forces tend to resist penetration and separation.
Categories (or Types) of Bloodstains
PASSIVE, Projected, and Transfer
TRANSFER BLOODSTAINS
A transfer bloodstain is created when a wet, bloody surface
comes in contact with a secondary surface.
A recognizable image of all or a portion of the original surface
may be observed in the pattern, as in the case of a bloody
hand or footwear.

Transfer bloodstains can be further subdivided into;
Contact bleeding
Swipe or Smear
Wipe
Smudge
PASSIVE BLOODSTAINS
Passive Bloodstains are drops created or formed by
the force of gravity acting alone.
PROJECTED BLOODSTAINS

Projected bloodstains are created when an exposed
blood source is subjected to an action or force, greater
than the force of gravity.  (Internally or Externally
produced)

(Think of swinging a bat!)

The size, shape, and number of resulting stains will
depend, primarily, on the amount of force utilized to
strike the blood source.
Dripped Blood                       Spilled Blood                   
Projected on a wall.
Swipe
LARGE VOLUMES OF BLOOD
(patterns created by same volume of blood, from
same source to target distance)
Footprint
This category can be further subdivided to
include;
*Arterial Spurt / Gush

Bloodstain pattern(s) resulting from blood
exiting the body under pressure
from a breached artery:
*Cast-off Stains

Blood released or thrown from a blood-bearing object in motion:
Projected through a syringe
*Impact Spatter

Blood stain patterns created when a blood source receives a blow or force resulting in
the random dispersion of smaller drops of blood.

This category can be further subdivided into;

•        Low Velocity

Gravitational pull up to 5 feet/sec.

Relatively large stains 4mm in size and greater
Medium Velocity

Force of 5 to 25 feet/sec.
Make a stain size 1 to 4mm in size

High Velocity
Force of 100 feet/sec. and greater

Makes a stain size 1mm in size and smaller
Mist like appearance
BLOODSTAINS ********* This is important for you to know. Mrs. B.  

When a droplet of blood strikes a surface perpendicular (90 degrees)
the resulting bloodstain will be circular.

That being the length and width of the stain will be equal.   

Blood that strikes a surface at an angle  less than  90 degrees will be
elongated or have a tear drop shape.

Directionality is usually obvious as the pointed end of the bloodstain ( tail )
will always point in the direction of travel.
Bloodspatter
Read the Bloodspatter information below.All of the information is important for you to know. We will be going
over this information in class and seeing some examples. Print off Bloodspatter info or take very good notes.
You'll be needing the information,