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Units of Practice

Crime Scene Investigation Using Blood Spatter Analysis

Unit Details


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

Abstract

Since students are fascinated by television shows and movies involving crime detection, using a forensic science approach could be a motivational tool for engaging students in the four included lessons. This approach for the analysis of blood spatter found at a "crime scene" is used to teach process and inquiry skills, including observation, measurement, and problem solving. The students will use open-ended investigations to draw comparisons between common phenomena and blood spatters. Using collected digital photos, an unknown blood spatter drop pattern will be compared, contrasted, and categorized.

Invitation/Fundamental Understandings:
Essential Questions:
Knowledge and skills:

Fundamental Understanding:
* Much of the scientific understanding is constructed through the
development of patterns and generalizations.
*Analyzing measurements is one effective tool used to create and
evaluate these patterns.

Essential Questions:
1. How are water droplets and blood droplets the same?
2. How does the trajectory, height, surface tension, and impact surface of a falling liquid affect the observed pattern?
3. How are measurements used in blood spatter investigations?
4. What are the legal ramifications of blood spatter analyses and how are these analyses used in forensic investigation?

Skills: comparative analysis, measuring, calculating, observing, graphing, collecting data, critical thinking, making inferences, problem solving, using spreadsheets, Internet research skills

Knowledge: measurement, angles, trajectories, surface tension, experimental design, characteristics of spatter patterns



Standards

National Standards

NSES CONTENT STANDARD: Unifying Concepts and Processes

TECHNOLOGY STANDARDS:
Students use a variety of media and formats to communicate information and ideas effectively to multiple audiences.

Students use technology to locate, evaluate, and collect information from a variety of sources.

Students use technology tools to process data and report results.

Students employ technology in the development of strategies for solving problems in the real world.

INFORMATION LITERACY STANDARDS:

Standard 1: The student who is information literate accesses information efficiently and effectively.

Standard 2: The student who is information literate evaluates information critically and competently.

Standard 3: The student who is information literate uses information accurately and creatively.

Standard 7: The student who contributes positively to the learning community and to society is information literate and recognizes the importance of information to a democratic society.

State Standards

Georgia: Process Skills Nevada: Process Skills #19

Workforce Competencies:

INFORMATION MANAGERS (3.1) NUMERIC PROBLEM SOLVERS (3.3) CREATIVE AND CRITICAL THINKERS (3.4) COOPERATIVE WORKERS (3.8)


Unit of Practice

Relevance:

Lies at the heart of the discipline: The core of good scientific practices is scientific inquiry. The basis of science inquiry is observation, data collection, and recognizing patterns. Represents a big idea: Recognizing patterns is a life-long skill that students can utilize in many different situations. The analyses represented in this unit can be applied to real life situations using forensic investigations. Misunderstandings: Many students may not realize that there are multiple factors that affect the spatter patterns of liquids. Engagement: Students have seen media accounts of crime scene investigations. The unit provides students the opportunity to participate in activities that culminate in the interpretation of blood spatters at a crime scene.

Context

This unit is designed to be used in a high school science class. Students will need to know the basics of experimental design. Scientific method should be discussed prior to this lesson, as well as the concepts of controlled and manipulated variables, data collection, graphing, independent and dependent variables, and measuring techniques. They should be familiar with the use of a digital camera, a spreadsheet program, Internet research and a graphing program.

Assessment

There will be formative assessments during the lessons such as a check of the students' experimental design, their graphs and their digital photo collection. A summative assessment will tie in all of the lessons and give insight into the students' understanding of the unit.

The students will produce a product at the culmination of the fourth lesson that demonstrates their understanding of the concepts addressed in this unit. The performance product that the students turn in will be of their own choosing. It can be either a formal lab report, a story, a forensics case study, a PowerPoint presentation, or any other type of presentation adhering to the parameters of the assignment.

In Lesson 1 dealing with water, simulated blood, and two other liquids the students will draw comparisons between blood and water properties of surface tension, viscosity, and specific gravity. The teacher can check for understanding by reviewing student responses to questions after this guided inquiry activity. Lesson 2 involves Internet research of a case study dealing with blood spatter patterns. The formative assessment will be the teacher critique of a short paragraph written by the student summarizing the case study. When the students determine an appropriate experimental design in the third lesson, the teacher will check for feasibility of the experiment. At the point when the students are displaying their data, such as the spreadsheet and the graphing activities, the teacher will check for correct relationships. The students will be collecting digital photos of their data that the teacher can also preview.

Components:

Lesson 1: Is Blood Thicker Than Water? In this lesson, students will investigate water properties and compare them to simulated blood properties. All students will be engaged by performing this hands-on experiment. Students will show what they have learned by answering questions in this guided inquiry lesson.

Lesson 2: Whodunit? In this lesson, students will read a case study while in small groups. They will write short paragraphs demonstrating what they have learned by reading the information and responding to the question: How is the information presented in the case study important to the forensic investigation of the crime? How is eyewitness testimony similar to forensic testimony? How is it different? Which would have greater influence on a jury's decision? Why?

Lesson 3: Pitter, Patter, Spatter Patterns In this lesson, students will design their own experiment showing how differences in height, impact surface, and angle affect the blood spatter patterns produced. All students will be engaged as they work in small groups to design and implement their procedures. Students will be taking digital photos of the trials and developing a database from which to compare the unknown spatter pattern in a subsequent lesson. They will also need to display their collected data in a spreadsheet and then graphically show their results.

Lesson 4: Murder Mystery: Catch the Clues In this lesson, students will work in the same groups as Lesson 3 and determine, by using the previous collected data, the height, impact surface, and angle of impact for an unknown sample in a mock crime scene. This lesson requires the students to make measurements at the "crime scene" and do a comparative analysis with information from Lesson 3. As a check for the accuracy of the students' results, students will be introduced to the "string method" for determining the origination of the blood spatter.


Additional Resources

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