Lesson #3: Pitter, Patter, Spatter Patterns

Lesson Details Subject: Science Learning Level: High School Author(s): Rich Fox, Chrissy Hemby, Karen Spaeth, Gloria Williams Submitted by:

Abstract This is the third lesson in a series investigating blood spatter patterns. In previous lessons students explored the similarities between blood and water and have analyzed a case study where blood spatter patterns were used in a forensic investigation. This sets the stage for this lesson where students will develop an experiment to test how the height, angle, and impact surface affect the "blood" spatter pattern. Students will use measurements as a tool to create and evaluate blood spatter patterns. Lesson fundamental understandings: Essential Questions: Analyzing measurements is one effective tool used to create and evaluate patterns. How does the trajectory, height, and impact surface of a falling liquid affect the observed pattern? How are measurements used in blood spatter investigations? Standards National Standards NSES STANDARD: Unifying Concepts and Processes TECHNOLOGY STANDARDS: Students use technology tools to process data and report results. State Standards Georgia: Process Skills Nevada: Process Skills #19 Lesson Prerequisite Skills Students should know... basic mathematics and measurement skills. how to use a digital camera. how to enter data into a spreadsheet. how to use a graphing program. basic elements of experimental design. basic safety skills. Teacher Information/Situations/Setting/Time Time Frame: 200 minutes Allow 50 minutes for experimental design. Allow 50 minutes to perform experiment and collect data. Allow 100 minutes to analyze data. Materials/Resources: digital camera computer with word processing, graphing, spreadsheet programs simulated blood rulers or meter sticks protractors Examples of impact surfaces: carpet, vinyl, plywood or hardwood, ceramic, concrete, etc string disposable pipettes Students should work in small groups of two or three. Pre-lesson Preparation: 1. Introduce students to the string method for determining the trajectory of spattered "blood" by having them read information regarding the "string method". (There are references to texts that can be used in the acknowledgments section of this lesson.) Run off copies for each student to be given as a homework assignment prior to the lesson, or have the students work in groups to complete the reading assignment. 2. Prepare simulated blood as follows: 160 mL corn syrup 80 mL water 44 g of corn starch 15 mLs-25 mLs red food coloring 2-3 drops green food coloring Mix the corn starch thoroughly with the water. Add the corn syrup. Mix well. Add red food coloring to the mixture using only 3 teaspoons at first. Then add a couple of drops of green food coloring to take the "pink" edge off the red coloring. If the mixture is too light, add one or two teaspoons more of red food coloring. Add an extra drop of green food coloring if the mixture gets too pink again. (Real blood is slightly on the dark red to reddish brown side when it is not fresh from the heart.) *This makes about 1 cup of simulated blood. 3. Gather lab and surface materials that will be available to the students. 4. Have students write experimental design. Check their procedure for design flaws or misunderstandings about controls, variables, etc. (about 50 minutes) 5. Have students perform their experiment. (about 50 minutes) 6. Provide students access to a computer to compile a file of the digital photos. Allow them to analyze their data using a spreadsheet to store numerical data and a graphing program to visually display the information. (about 100 minutes) 7. The information that the students compile will be used in the next lesson to analyze a "crime scene" scenario. Assessment Formatively, the teacher should check several understandings during the lesson. After the students design their experiment, the procedure should be checked before they are allowed to proceed. A rubric for experimental design that the teacher could use is Science #301 or #302. As students collect and organize their data, check and comment on their photo files, their spreadsheets, and their graphical illustrations. Student Activity/Tasks Student Activity: Part A: Experimental Design 1. In this activity you will design an experiment that will test for the differences in spatter patterns produced by simulated blood. The variables to be tested include height and angle of the spattered blood and the impact surface. Your teacher will tell you what surfaces are available to you to be tested. While you are developing your procedure remember the proper use of controls and variables. 2. When your experimental design is complete, have your teacher approve the design before going on to Part B. Part B: Performing the Experiment 1. While collecting data, take digital photos of all the spatter patterns. 2. Using the digital photos, build a file of photos using a computer program of your choice. 3. Use a spreadsheet program to enter numerical data collected from the spatter patterns. 4. Use a graphing program to display the relationship between the variables. A line graph will probably best show the displayed data. 5. The collected information from this lab will be used in the next lesson when determining the unknown direction and height of spattered "blood" in a mock crime scene. Enrichment/Alternate Activity: As an alternative to the hands-on activity, students could use published sources to find different blood spatter patterns. Have students build a file using this published data. Cross-Curricular: Forensic science mathematics Technology Requirements/Tools/Materials Digital camera Computer Word processing software Spreadsheet software Graphing software Acknowledgements: Books: Bloodstain Patterns by Herbert Leon MacDonell (Published by Laboratory of Forensic Scientists, PO Box 1111, Corning, NY 14830) Blood Pattern Analysis with an Introduction to Crime Scene Reconstruction (CRC Series in Practical Aspects of Criminal and Forensic Investigations) by Tom Bevel and Ross M. Gardner ISBN # 0849381592 (Available on www.amazon.com) Bloodstain Evidence Manual by Judy Bunker (Published by the Institute of Applied Forensic Technology) Interpretation of Bloodstain Evidence at Crime Scenes by Stuart James and William Eckert (Published by CRC) Additional Resources Main URL: Related Lessons Related Resources Copyright © 1997-2003 Career Connection to Teaching with Technology USDOE Technology Innovation Challenge Grant Marshall Ransom, Project Manager All rights reserved.