Blood Spatter - Understanding the Clues

by

Introduction

Violent crimes often result in bloody scenes which are distracting. But the blood itself, as well as the spatter patterns it forms, tells the story of what happened. Each drop of blood is a paragraph in the story which was written by the laws of physics and biochemistry. Varying blood types at a crime scene means that more than one person was involved and injured. Size of the drops gives us a clue as to the velocity that the blood reached prior to impact. This, in turn, is a clue to the nature of the weapon used to inflict the injury. The shape of the blood drops and their proportions tell the investigator what the trajectory was of each drop. With this information we can begin to reconstruct the crime, including movement of the victim, position of the suspect and the number of times the victim was struck.

All we have to do is learn how to read the story. That's what this lesson is about.

Lesson Time

Blood Spatter Analysis
4 Class Periods

Industries / Subjects / Grades

Industries / Pathways
  • Public Services
K-12 Subjects
  • English-Language Arts
Grade Levels
  • 10
  • 11
  • 12

Standards and Objectives

Standards

California Academic Content Standards (5)
California's 2008 CTE Standards (3)

Related Instructional Objectives (SWBAT...)

  • Students will list and explain the terms used in analyzing blood spatter evidence.
  • Given three or more stains from drops of simulated blood, students will determine the direction of travel and the angle of impact for each drop. Do not use real blood for this lesson as there are several issues that can arise.
  • Students will list the 6 categories of blood stain patterns identified by John Glaister and explain what the presence of each pattern tells the investigator about the actions that took place during a crime.

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