modern application for introductory physics bloodstain pattern analysis l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Modern Application for Introductory Physics: Bloodstain Pattern Analysis PowerPoint Presentation
Download Presentation
Modern Application for Introductory Physics: Bloodstain Pattern Analysis

Loading in 2 Seconds...

play fullscreen
1 / 26

Modern Application for Introductory Physics: Bloodstain Pattern Analysis - PowerPoint PPT Presentation


  • 253 Views
  • Uploaded on

Modern Application for Introductory Physics: Bloodstain Pattern Analysis. John Eric Goff Lynchburg College. 2005 Spring Meeting Lynchburg College Lynchburg, VA 24501. New Field of Interest: Forensic Science. Television shows and movies influence student interests.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Modern Application for Introductory Physics: Bloodstain Pattern Analysis' - moke


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
modern application for introductory physics bloodstain pattern analysis

Modern Application for Introductory Physics: Bloodstain Pattern Analysis

John Eric Goff

Lynchburg College

2005 Spring Meeting

Lynchburg College

Lynchburg, VA 24501

new field of interest forensic science
New Field of Interest:Forensic Science
  • Television shows and movies influence student interests.
  • Forensic Science courses, minors, and majors are springing up around the country. (New course here at LC!)
  • Watch for some very BAD science on TV and in movies!
forensic science is very interdisciplinary
Biology

Chemistry

Physics

Mathematics

Law

Psychology

Sociology

Biochemistry

Biophysics

Physical Chemistry

Environmental Science

Handwriting

Medicine

Hobbies???

Forensic Science isVERY Interdisciplinary!!!
i got help with this talk

I got help with this talk!

http://www.bloodspatter.com/

(The tutorial is great! However, beware of some poor physics in a few places!)

bloodstain patterns
Bloodstain Patterns
  • Physical Evidence
  • Usually Found at Violent Crime Scenes
  • Gives Clues as to WHAT Happened
  • May Suggest Sequence of Events
  • Analysis MUST be placed in context of all aspects of crime scene investigation in order to reconstruct (possible) criminal events.
different types of bloodstain patterns
Different Types of Bloodstain Patterns
  • Passive Bloodstains (drops, pools, etc.)
  • Transfer Bloodstains (wipe a weapon, etc.)
  • Active (or “Projected”) Bloodstains (bullets, stepping in blood, etc.)
active or projected bloodstains
Active (or “Projected”) Bloodstains
  • Rule of Thumb: As impact angle goes down, bloodstain shape becomes more elongated.
active or projected bloodstains8
Active (or “Projected”) Bloodstains
  • Impact Spatter – Blood source is “smacked” in some way and drops fly off in various directions.
  • Divide category further by blood’s impact speed.
low velocity
Low Velocity
  • velocity ≤ 5 ft/s
  • stain size is (relatively) large: diameter ≥ 4mm
  • examples: blood drops into blood and footstep spatters
medium velocity
Medium Velocity
  • 5 ft/s ≤ velocity ≤ 25 ft/s
  • stain size : 1 mm ≤ diameter ≤ 4mm
  • examples: blood flicked off finger and blunt object used on victim
high velocity
High Velocity
  • velocity ≥ 100 ft/s ( 68 mph)
  • stain size (relatively small): diameter ≤ 1mm
  • examples: gunshots and propellers
time for physics
Time for Physics!
  • Big Forensic Science Question: “From where did the blood come???”
slide13

Try this!

one exception!

tail points in

direction of

travel

slide14

sin θ = W / L

W

L

What does W = L mean?

sin θ = 1 → θ = 90

Drop is a circle!

real world
Real World!
  • What if blood drop is not a pretty oval?!?

Do the best you can!!!

physics and math
Physics and Math
  • Work backwards from blood spatter to determine “launch position” of blood.
  • BE AWARE of all approximations that are used in analysis! (This is a great example for teaching students about approximations in physics.)
big problem
Big Problem!!!
  • Neither blood nor anything else travels unaided in a straight line through the air!
example

parallel to ground

θ = -10

1 m

v = 20 ft/s

ground

Example
  • Consider “medium velocity” blood drop of diameter 3 mm “launched” at a position 1 m off the ground.
  • Numbers: v = 20 ft/s (6 m/s) & θ = -10
slide24

What about air resistance???

(Drop’s speed and size are

needed. Tough to know!)

What about gravity???

moral of the story
Moral of the Story
  • Calculation using “straight-line” trajectory (no gravity and no air resistance) predicts a “launch” point higher than actual point.
  • “Straight-line” trajectory is reasonable for high “launch” velocities and/or stain and “launch” points “close” together. (The idea is to keep the flight time as short as possible.)
  • More accuracy requires a better model and more specialized work.
forensic science literature
Forensic Science Literature

The Directional Analysis of Bloodstain Patterns: Theory and Experimental Validation by A. L. Carter

  • “Therefore, the best one can do here is to estimate an upper limit for the height of the source.” (p. 181)

Can. Soc. Forens. Sci. J. Vol. 34. No. 4 (2001) pp. 173-189