Bloodstain pattern analysis examines the size, shape, distribution and location of bloodstains at a crime scene to determine what happened. There are three main types of bloodstains: passive stains from gravity, transfer stains from direct contact, and spatter stains from force acting on liquid blood. Analysts also consider the shape and direction of stains, type of injury, and can use chemicals like Luminol to find latent stains not visible to the naked eye.

1. BLOODSTAIN
PATTERN
ANALYSIS
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2. What is Bloodstain
pattern analysis?
Bloodstain pattern analysis (BPA)
is the interpretation of bloodstains
at a crime scene in order to recreate
the actions that caused the
bloodshed. Analysts examine the
size, shape, distribution and
location of the bloodstains to form
opinions about what happened.
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3. Types of Stains:
Transfers occur when a blood source
comes in direct contact with a target
surface area, such as a bloody shoe print or
a smear from a body being dragged.
1) TRANSFER:
Passive stains include drops, flows and
pools, and typically result from gravity
acting on an injured body.
2) PASSIVE:
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4. @cmcriminologist
Spatters are produced when a
source of liquid blood is acted
upon by an external force. The
blood droplets, created by the
force, travel through the air
before landing on a target
As a general rule; the greater
the amount of force applied to
the source of liquid blood, the
smaller the resulting blood
spatters.
Spatters on a suspects clothing
or person, may indicate that he
was in direct proximity, to the
blood source, at the time the
force was being applied
3) SPATTERS:

5. @cmcriminologist
Shapes:
The shape of
the bloodstain
varies
according to
the angle of
impact...

6. ...and the type of
surface. Stains on a
smooth surface will
make a more
uniform, circular
shape with smooth
edges.
Drip stains on a
course surface will
make an irregular
shaped stain with
rough or jagged edges.
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7. Height & Direction:
The higher the
height the bigger is
the radius of the
blood spot.
The tail of the
elongated drop
points to the travel
direction.
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8. Type of Injury & Blood Stains:
Sharp force injuries (stabbing): these injuries are
caused by an object with a relatively small
surface area, such as an ice pick or a knife. Less
blood is deposited on the instrument, resulting
in a smaller, more linear pattern of stains.
Blunt force injuries (hitting or beating) - objects
inflicting this type of injury are usually larger,
such as a bat or hammer. If the object impacts
liquid blood, the larger surface area will collect
more blood, producing drops of varying sizes.
Gunshot injuries - mist-like spatter caused by
bullets entering and exiting the body.
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9. Latent Bloodstains:
Some bloodstains are latent, meaning they
cannot be seen with the naked eye.
Investigators can use chemical reagents such as
Luminol to find and photograph latent
bloodstains. When sprayed on blood,
Luminol creates a bright blue luminescent glow
by reacting with iron in the blood’s hemoglobin.
However, if surfaces and clothes are washed
with products containing active oxygen, the
luminol test gives a negative result.
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