Bloodstain Patterns
Kevin Sami
What is Bloodstain Pattern
Interpretation?
Bloodstain Pattern Interpretation
involves reconstructing the events
that occurred to produce the
bleeding.
Bloodstain Patterns can
determine…
 Origin(s) of bloodstain
 Angle of impact
 Direction of impact
 Speed with which blood left its source
 Position of victim & assailant
Determining Origin of Bloodstain
The origin can be established
by drawing straight lines through
the long axis of several individual
bloodstains.
Points of Convergence
Point (Area) of Convergence -- The
common point (area), over which
the several blood drops can be
retraced
Angle of Impact
Angle of Impact -formed between
the direction of
a blood drop
and the surface
it strikes
90
80
70
60
50
40
30
20
10
Adapted from
Introduction to Forensic Sciences,
W. Eckert, CRC, 1997
It is possible to determine the impact angle of
blood on a flat surface by measuring the degree
of circular distortion of the stain.
Direction of impact
•The pointed end of a bloodstain
always faces its direction
of travel.
Speed of Impact
•As a general rule, the higher the energy of the impact, the
smaller the drops are.
•Free-falling blood has a low velocity, leaving large drops.
Speed of Impact (cont.)
• Impact spatters, found in
cases of beating or
stabbing, are mediumvelocity.
• High-velocity impact
patterns appear as a
mistlike spray of droplets
with a few larger droplets
mixed in.
Cast-Off Pattern
Cast-Off Pattern -- A bloodstain
pattern created when blood is released
or thrown from a blood-bearing object
in motion.
victim
Cast off from Weapons
 First blow to victim
causes bleeding.
 Further attacks cause
blood cast off onto
surrounding area.
Position of Victim and
Assailant
•The point of convergence and
the angle of impact locate the
area where victim was.
•Low- and medium-velocity
spatters can mark the attacker
with backspatter.
•Any Void spaces in
bloodspatter is the possible
location for assailant.
Surface effect on
Bloodspatter
The harder the surface is, the less spatter will result.
Surface 1
Surface 2
Surface 3
Single drop of blood falling from various heights (m) onto vario us surfaces
0.5
0.5
1
1
Height/Surface
2
2
3
3
smooth
floor
paper
towel
fabric
Bibliography
•http://www.dundee.ac.uk/forensicmedicine/notes/Bloodspatter.htm
•http://www.suite101.com/article.cfm/crime_stories/34498
•http://www.brazoria-county.com/sheriff/id/blood/bloodspatter_general.htm
•http://www.brazoria-county.com/sheriff/id/blood/terminology.htm
•http://www.brazoria-county.com/sheriff/id/index.htm
•file:///C:/Documents%20and%20Settings/Owner/Local%20Settings/Tempora
ry%20Internet%20Files/Content.IE5/4LAFO9MR/2%2520Blood%2520Spatt
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