Blood Spatter Pattern Analysis
Grade Level
& Duration:
11/12
2 – 50 min
periods
Subject:
Forensics
Prepared By:
Carol Clinton
Analyze Learners
Overview & Purpose (STEMcinnati theme)
Education Standards Addressed
Ratios and Proportional Reasoning
Beginning with surface tension, a basic property of
fluids, students study the math and science of blood
spatter pattern analysis. They design and conduct
experiments to study the effect of variables including
travel path length, angle of impact, and surface of
impact. Then they analyze the resulting stains using
basic trig functions to calculate the angle of impact, and
graph the relationships between variables to create
tools that will allow them to solve an unknown “crime
scene” scenario (that is a separate activity that will be
their final exam).
Applications to the real world : Techniques used in this
lesson are the actual laboratory methods used by
government forensics labs to generate information that
is used to solve crimes. (video clips from the Midwest
Forensics Research Center are used as part of the
lesson).
MA-HS-1.4.1
Students will apply ratios, percents and proportional reasoning to solve real-world problems (e.g., those
involving slope and rate, percent of increase and decrease) and will explain how slope determines a rate of
change in linear functions representing real-world problems.
MA-HS-2.1.3
Students will apply definitions and properties of right triangle relationships (right triangle trigonometry and
the Pythagorean theorem) to determine length and angle measures to solve real-world and mathematical
problems.
MA-HS-3.1.11
Students will visualize solids and surfaces in three-dimensional space when given two-dimensional
representations (e.g., nets, multiple views) and create two-dimensional representations for the surfaces of
three-dimensional objects.
MA-HS-4.1.1
Students will analyze and make inferences from a set of data with no more than two variables, and will
analyze problems for the use and misuse of data representations.
MA-HS-4.1.2
Students will construct data displays for data with no more than two variables.
MA-HS-4.3.2
Students will design simple experiments or investigations to collect data to answer questions of interest.
Societal impact: Unfortunately, we live in a world where
violent crimes occur. Science and math can be used to
help solve such crimes and bring justice.
Career connections: Math and science concepts such
as the ones in this lesson are applicable to a wide
variety of fields, from all types of engineering, to law
enforcement and forensics research, to accurate screen
writing for hit shows like the CSI series.
Select Goals
and Objectives
Teacher Guide
Student
Guide
Goals and
Objectives
(Specify
skills/information
that will be
learned.)
Select
Instructional
Strategies –
Information
(Give and/or
demonstrate
necessary
information)
1. Bloodstain patterns
 Define blood spatter patterns
 Calculate the impact angle of blood spots
 Describe the physical properties of blood that have an
impact on bloodstain pattern analysis
Day 1:
Photos and videos of blood spatter are used to capture attention.
http://www.nfstc.org/links/animations/images/blood%20spatters.swf
http://files.mfrc.ameslab.gov/
1Aa2 Blood dripping from a wrench handle.avi
3Da1a Blood drop falling 10 cm onto carpet.avi
3Fa1a Blood drop falling 10 cm onto wood.avi
3Fb2a Blood drop falling 100 cm onto wood (1).avi
4Ai2 Blood drop falling to a 90 degree target (top view).avi
4Ad1 Blood drop falling to a 40 degree target (front view).avi
4Ad1 Blood drop falling to a 40 degree target (side view).avi
Materials Needed (22 students in groups of 2 = 11
groups)
 Clipboards – one per group
 Meter sticks
 Small rulers (mm)
 protractors
 Paper 8-1/2 x 11 graph paper
 Sheets of other light colored materials (e.g., fabric,
wallpaper, plexiglass, plastic wrap, plywood)
 Pencils/pens/sharpie markers
 Masking tape
 Fake blood:
- Flinn Bloodstain Pattern Analysis Kit FB1643
http://www.flinnsci.com $32.95
- (alternative kit Ward’s Blood Spatter Analysis Lab
Activities $79.95 http://wardsci.com)
- Or make your own from recipes at
http://www.clt.uwa.edu.au/asistm/forensic_investigations/
bloodstain_pattern_analysis
The Day 1 powerpoint presentation (~ 20 minutes) gives details
about the principles of blood spatter pattern analysis.
The lab is introduced. Teams are chosen and begin designing
their experiments. Depending on length of instructional period, lab
can be conducted on day 1 to generate “blood” spatter patterns
under controlled conditions.
Day 2:
Discuss results of pattern generation lab, conduct the analysis
portion (measuring stains, computing angle of impact, graphing
relationships between variables).
Utilize
Technology
Internet video clips and powerpoint presentation are used to
transmit information.
Students use simple equipment (fake blood, pipets, rulers,
protractors, and a variety of everyday materials as the impact
surfaces) to conduct experiments and generate spatter patterns.
Students use calculators and graph paper to analyze resulting
patterns.
Other Resources
(e.g. Web, books, etc.)
Bloodstain Pattern Analysis Tutorial By: J. Slemko
Forensic Consulting
http://www.bloodspatter.com/BPATutorial.htm
Require
Learner
Participation
Activity
(Describe the
independent
activity to
reinforce this
lesson)
Evaluate
(Assessment)
(Steps to check
for student
understanding)
Your goal is to figure out what conditions caused the patterns
found at the “crime scene.” Design and conduct experiments to
gather data and formulate hypothesis that will allow you to
reconstruct events.
Day 1:
Create blood spatter patterns with drops from different angles of
impact and different heights on different surfaces.
Day 2
From drop patterns: Measure diameters, widths and lengths of final
(dried) drops. Create tables to report data. Graph diameter of
drops vs. height. Determine angle of impact from width and length
of drops using the arcsine trigonometry relationship. Graph angle
of impact vs. width and vs. length of drops.
Essential questions:
- what are some key variables in the resulting patterns of blood
spatter? Drop height, surface it lands on (roughness,
perviousness), angle of impact, placement of drops (on previous
drops, pool, etc)
- what is the effect of greater drop height? Larger stain Why?
Increased energy (kinetic) allows farther spread
- what is the effect of angle? Greater length of stain compared to
width
- how can you tell from a stain what the angle of impact was? Trig
(arc sine, or “inverse sine” of width/length ratio)
Additional Notes
Reflection:
Of course, the students loved the video clips from the Ames lab (Midwest Forensics Research Center) of blood dripping, spurting, flung, etc! And
they generally enjoyed the lab. However, I discovered that several of them did not know how to read a protractor and did not understand that
when you drop from height, it’s the impact surface that needs to be at an angle from horizontal. Some thought that holding the pipette at an angle
would work and got frustrated when the patterns were the same no matter what angle they held the pipette (which should have been a clue for
them…).
I ended up creating the supplemental powerpoint presentation on impact angle that goes into more detail on this.
I was surprised that some got frustrated with the freedom of being able to design their own experiments. I provided a variety of surface materials
and left it to them to choose their own angles, heights, and other variables. Some wanted a “cook book” of exactly what to do and got perturbed
when I wouldn’t tell them.
The graphing took more time than I thought it should. And many students didn’t understand the concept of arc sine, so I had to go back and
review trigonometry in more detail (see the supplementary powerpoint presentation).