Ch. 8: Blood Spatter
What constitutes a “blood spatter pattern”?
I. History of Blood-Spatter Analysis
Who was the first researcher to analyze the meaning of the spatter pattern?
____________________, in the year ______________.
One of the earliest cases to use blood-spatter was in 1955 in the __________________
case. The blood-spatter evidence helped to ________________ him.
Dr. Herbert MacDonnell analyzed blood-spatter in what famous case? _______________.
II. Blood-Spatter Analysis
A. Four pieces of information that can be gained from blood-spatter analysis are:
1. ____________________________________________
2. ____________________________________________
3. ____________________________________________
4. ____________________________________________
B. Blood is a thick mixture of _______________ and _________________.
C. Four factors that affect how a blood droplet forms are
1. Gravity: ________________________________________________
Ex:
2. Cohesion: _______________________________________________
Ex:
If blood overcomes cohesion and separates from the main droplet of
blood, it will form small secondary droplets known as
____________________________.
3. Adhesion: _______________________________________________
Ex:
4. Surface tension: __________________________________________
Ex:
D. When will spikes or extension occur in a blood drop?
E. Blood spatter classifications (there are 6): How created and what do they tell?
1. Passive fall:
2. Gushes (arterial spurts):
3. Splashes:
4. Smears:
5. Trails of blood:
6. Pools:
F. Determining the Type of Wound
1. A fine mist pattern =
2. Lower velocity pattern =
3. Voids might tell us =
4. Point of Origin: (use definition in back of book!)
III. Examination of Directionality of Blood
A. A circular drop of blood indicates that the blood _____________________
____________________________________________________________
B. An elongated drop of blood can tell us ______________________________
C. What are those three forces again that affect a moving drop of blood?
____________________________________________________________
Which one did they forget that you learned about earlier? ________________
D. Due to adhesion, the point of impact may appear to be _______________ and
_______________ than the rest of the drop of blood spatter.
E. What is momentum? (you might have to look this up on the Internet!) _________
______________________________________________________________.
How does this relate to Newton’s 1st Law of Motion? _______________________
______________________________________________________________.
Momentum tends to keep the blood ____________________________________.
Direction of movement?
F. As blood droplets move away from their source, the blood droplet
_____________________ and may produce a thinner _____________________.
The tail points in the direction of the blood’s ____________________________.
Satellites that break off will appear ____________________ the moving droplet.
IV. Lines of Convergence
A. The location of the source of blood can be determined if there are at least
______ drops of blood spatter.
B. By drawing lines down the long axis of the blood spatter and noting where the
lines intersect, you can determine the ________________________________.
C. If there are numerous blood spatters, how do you find the source where the
blood originated? ________________________________________________
V. Blood Spatter Types
Examine the bloodstain pattern below. Determine the number of each size drop. Find the
percent frequency of each droplet size and determine which size is preponderant (more
common).
Width of stain
Stain size
(width in mm)
# of stains
%
Frequency
Upon examining blood spatter in many crime scenes, forensic experts noticed a relationship
between the size of a blood spatter and the velocity of the wounding agent. This
relationship led them to a vital clue in deciphering the type of weapon or wounding agent
that caused the blood spatter at a crime scene. The impact velocity was categorized as low
impact, medium impact, or high impact velocity.
Experts have determined that a low-impact velocity wounding agent generally produces a
spatter of at least 4 mm in size. A medium-impact velocity wounding agent produces spatter
with size between 1 and 4 mm. A high-impact wounding agent produces spatter with size
ranging from 0.1 to 1 mm. Summarize this information in the table below.
Type of
Velocity Range
Spatter Size
Possible Wounding
Impact
(width of droplets)
Agents
According to the data that you tabulated above, what is the relationship between the
impact velocity of the wounding agent or weapon and the size of the blood spatter?
Velocity
(v)
Based on what you’ve learned,
give a possible wounding
agent that produced the
pattern?
Preponderant
Stain Size (s)