Blood Spatter Activity

Introduction

“In the world of serious crime, nice clean fingerprints don’t come around that often.

Investigators have to work with what they have-be it a footprint or a shred of DNA, and the science of forensics is constantly evolving to help us understand the most impenetrable of crime scenes.

Meet the blood-spatter expert, the foot morphologist, and the forensic dentist, and see how their painstaking work is catching the ones who got away.”

THE CRIME SCENETHE CRIME SCENE

“On the night of August 16, 1991, in a house in Apohaqui, New Brunswick, in a case that shocked a small town community, blood splatter expert Pat Laturnus was called in to investigate a tragic accident that had left a woman dead.

Her husband was distraught but something about his story was not adding up and the evidence began to tell another story altogether. . . .”

Let’s take a look at the crime scene as it unfolds. . .

http://www.thehistorychannel.co.uk/site/tv_guide/full_details/Crime/programme_2728.php

Blood Splatter Evidence Activity Blood spatter evidence plays a key part in

forensic analysis. We are going to see how reliably we can predict the height of a blood drop of known diameter, if we are able to measure diameter and precisely plot the relationship between these two variables.

Introduction continued…… Blood drop evidence has been collected

from a piece of paper laid on the floor, and blood droplets were released from perpendicular locations of various heights.

We will assume that DNA fingerprinting has already been used to determine that these drops came from our victim.

Directions for Analysis of Blood Drop Size

Data collection will be done in a small group.

Each group will receive a copy of the results of blood dropped from heights of 0.5m, 1.0m, 1.5m, 2.0m, 2.5m, and 3.0m.

Analysis continued….. Measure the diameter (in mm) of the drop

for each of the different distances dropped. Fill in the data table on your worksheet.

Follow the directions to generate a regression model that best fits your data.

The demise of John WayneJohn Wayne was

wounded while trying to rescue his sister from Apache Indians. His body has not been recovered.

In an attempt to recreate the tragedy, we have asked forensic/math students (you) to determine the height of the wound from blood spatter evidence left at the scene.

Blood spatter evidence recovered. Determine the diameter of the blood spatter

evidence collected from the scene and determine the height from which the blood drop fell. (This may reflect the height of the wound and help determine the site.)

Article Review:Article Review: Read “Bloodstain pattern analysis Read “Bloodstain pattern analysis

tutorial” by tutorial” by J. Slemko Forensic J. Slemko Forensic ConsultingConsulting. .

Complete the guided reading Complete the guided reading questions on your worksheet. questions on your worksheet.

BLOOD SPATTER LABBLOOD SPATTER LAB Relationship Between Blood Drop Shape Relationship Between Blood Drop Shape

and Impact Angleand Impact Angle

Materials Needed per GroupMaterials Needed per Group Simulated Drip and Projected BloodSimulated Drip and Projected Blood 5 X 8 notecards5 X 8 notecards 15 cm and 30 cm rulers15 cm and 30 cm rulers Impact angle apparatus Impact angle apparatus TapeTape

Assembling the Impact angle Assembling the Impact angle apparatusapparatus

Tape one end of the clipboard to a table Tape one end of the clipboard to a table by making a hinge out of tape. The by making a hinge out of tape. The clipboard should be right at the edge of the clipboard should be right at the edge of the table. Hold the protector to the edge of table. Hold the protector to the edge of the clipboard so that the protractor is the clipboard so that the protractor is perpendicular to the table top and aligned perpendicular to the table top and aligned so that the center of the protractor is at the so that the center of the protractor is at the edge of the hinged-end of the clipboard. edge of the hinged-end of the clipboard.

See the figure in the next slide. See the figure in the next slide.

Impact Angle Apparatus Impact Angle Apparatus

Table

Tape

Clipboard

30º

60°

Protractor

Select an Impact Angle to StudySelect an Impact Angle to Study

Your data table (on your worksheet) Your data table (on your worksheet) includes angles from 10includes angles from 10° to 90°. ° to 90°.

Once you have selected an impact angle, Once you have selected an impact angle,

indicate the angle on the card and then indicate the angle on the card and then attach the card to the board.attach the card to the board.

ClipboardClipboard

Clip

Notecard

Clipboard

Directions continued….Directions continued…. Set the angle of the board using the Set the angle of the board using the

protractor so that the board will have the protractor so that the board will have the correct impact angle. You will need to work correct impact angle. You will need to work together as a team to achieve this.together as a team to achieve this.

To obtain the desired impact angle, set the To obtain the desired impact angle, set the impact angle board to a protractor setting impact angle board to a protractor setting of 90of 90° minus the desired impact angle. ° minus the desired impact angle. (For example, to obtain a 60° impact (For example, to obtain a 60° impact angle, set the board at a protractor setting angle, set the board at a protractor setting of 30°). of 30°).

Directions continued….Directions continued…. Using the Simulated Drip and Projected Blood, Using the Simulated Drip and Projected Blood,

place the dropper at approximately 30 cm above place the dropper at approximately 30 cm above the impact angle board. the impact angle board.

Allow two to three drops to fall sequentially onto Allow two to three drops to fall sequentially onto the card. Move your hand so that the drops the card. Move your hand so that the drops don’t overlap. Using multiple drops will allow don’t overlap. Using multiple drops will allow you to see the variation that single drops may you to see the variation that single drops may display when striking the surface. Leave the display when striking the surface. Leave the card in position for 2-3 minutes before carefully card in position for 2-3 minutes before carefully removing it. removing it.

Directions continued…..Directions continued…..

Allow the drops to dry thoroughly on the Allow the drops to dry thoroughly on the cards and then store in a safe place.cards and then store in a safe place.

When we return, we will record your When we return, we will record your observations including a sketch in the data observations including a sketch in the data table provided. We will also include the table provided. We will also include the diameter and length of the circle or ellipse diameter and length of the circle or ellipse created. created.

Calculations with Blood SpattersCalculations with Blood Spatters To find the To find the point of hemorrhage (POH)point of hemorrhage (POH), ,

you must first determine the two-you must first determine the two-dimensional dimensional point of convergence (POC).point of convergence (POC). The POC is the intersection where lines The POC is the intersection where lines drawn through the center of the individual drawn through the center of the individual drops meet (at the X-Y axis intersection). drops meet (at the X-Y axis intersection).

This is determined by drawing lines or This is determined by drawing lines or placing strings through the long axis of placing strings through the long axis of individual spatters.individual spatters.

Point of Convergence (POC)Point of Convergence (POC)

Can you complete this one?Can you complete this one?

Angle of Impact (AOI)Angle of Impact (AOI)

The AOI for representative bloodstains The AOI for representative bloodstains helps to generate the 3helps to generate the 3rdrd dimension dimension (z-axis) in a crime scene. (z-axis) in a crime scene.

This shows how high up off the ground This shows how high up off the ground the impact occurred.the impact occurred.

To Determine the Angle of Impact To Determine the Angle of Impact (AOI):(AOI):

i.i. Where opposite = width (W) and Where opposite = width (W) and hypotenuse = length (L) hypotenuse = length (L)

i.i. Angle of impact = ArcSIN of W/L ratioAngle of impact = ArcSIN of W/L ratioa)a) First calculate ratio (W/L)First calculate ratio (W/L)b)b) You should remember that you can use You should remember that you can use

SINSIN-1-1(2(2ndnd key) to get degree of AOI. key) to get degree of AOI.

To complete our Blood Spatter To complete our Blood Spatter ProjectProject . . . . . .

In a small group, look over the In a small group, look over the information gathered from the Blood information gathered from the Blood Spatter Lab activity.Spatter Lab activity.

Complete the lab analysis worksheet Complete the lab analysis worksheet provided.provided.

CitationsCitations www.historychannel.co.uk

www.bloodsplatter.com/BPAtutorial.htm

www.marshall.edu/cellcentral/GHA/cabinblood.htm

www.marshall.edu/cellcentral/GHA/blooddroplab.htm

The Forensic Examiner – Summer 2005: Article by The Forensic Examiner – Summer 2005: Article by Louis L. Akin, LPILouis L. Akin, LPI

Bloodstain Pattern Analysis tutorial by J. Slemko forensic Bloodstain Pattern Analysis tutorial by J. Slemko forensic consultingconsulting

Citations, continued.Citations, continued. Ward’s bloodspatter analysis lab Ward’s bloodspatter analysis lab

kitBloodstain kitBloodstain Pattern Analysis tutorial by J. Slemko Pattern Analysis tutorial by J. Slemko

forensic consultingforensic consulting