Forensic Science Worksheet for 17-Year-Olds | High School Science Activity

Instructions

Read each section carefully and answer the questions to the best of your ability. This worksheet will test your knowledge of fundamental concepts in forensic science, from evidence collection principles to biological and physical analysis.

Part 1: Vocabulary Matching

Match the forensic science term in Column A with its correct definition in Column B. Write the letter of the correct definition in the space provided.

Part 2: Critical Thinking

Answer the following questions in complete sentences.

1. Describe the three primary fingerprint patterns. Which is the most common in the human population, and which is the least common?
2. A body is discovered at a crime scene. Paramedics note the presence of fixed lividity along the deceased's back. However, the body is found lying in a prone (face-down) position. What might this discrepancy indicate to a forensic investigator?
3. Explain the importance of the "Chain of Custody" in a criminal investigation. What is the potential legal consequence if the Chain of Custody is broken or poorly documented?

Part 3: Case Study Analysis

Read the following scenario and answer the questions that follow.

Investigators are called to a residential address following a report of a home invasion. The homeowner was out of town. The front door is locked, but a rear kitchen window is smashed. A small amount of what appears to be blood is found on a sharp edge of the broken glass. On the linoleum floor below the window, investigators find a muddy shoeprint with a distinct tread pattern. A single, dark strand of hair is found caught on the kitchen counter near the open drawers.

1. Identify three distinct pieces of physical evidence from the scenario.
2. For each piece of evidence you identified, classify it as potentially individual evidence or class evidence. Justify your reasoning.
3. What forensic specialist or unit would be responsible for analyzing each piece of evidence you identified? (e.g., who analyzes the blood, shoeprint, and hair?)

Answer Key

Part 1: Vocabulary Matching

1. D. The principle that every contact between two objects results in a mutual exchange of material.
2. C. The chronological documentation showing the seizure, custody, control, transfer, analysis, and disposition of evidence.
3. G. The postmortem cooling of the body to the surrounding temperature.
4. A. The postmortem pooling of blood in the body due to gravity, causing a purplish-red discoloration of the skin.
5. B. The unique ridge characteristics (e.g., ridge endings, bifurcations) of a fingerprint used for identification.
6. E. The study of firearms, including the firing of a weapon and the flight of a bullet.
7. F. Material that can be associated only with a group of items that share properties or characteristics.

Part 2: Critical Thinking

1. The three primary fingerprint patterns are Loops, Whorls, and Arches. Loops are the most common pattern (approximately 60-65% of the population), while Arches are the least common (approximately 5% of the population). Whorls account for the remaining 30-35%.
2. Fixed lividity (livor mortis) indicates that blood has settled in the parts of the body closest to the ground for a significant period (typically 8-12 hours) after death. If the lividity is fixed on the back, but the body is found face down, it strongly suggests that the body was moved several hours after death. The person died lying on their back and was later turned over.
3. The Chain of Custody is a written record that proves the integrity of a piece of evidence by tracking everyone who has handled it from collection to its appearance in court. It is crucial for ensuring that the evidence has not been tampered with, contaminated, or replaced. If the Chain of Custody is broken, the defense can argue that the evidence is unreliable, and the judge may rule it inadmissible, meaning it cannot be used in the trial.

Part 3: Case Study Analysis

1. Three pieces of evidence are:
   • The blood on the broken glass.
   • The muddy shoeprint on the floor.
   • The strand of hair on the counter.
2. • Blood: This is potentially individual evidence. While blood type is class evidence, if a sufficient sample is recovered, a DNA profile can be generated. A DNA profile is unique to an individual (except for identical twins), linking the sample directly to a specific person.
   • Shoeprint: This starts as class evidence, as the tread pattern can be linked to a specific brand and model of shoe worn by thousands of people. However, it can become individual evidence if it has unique wear patterns, nicks, or embedded debris that can link it to one specific shoe.
   • Hair: A hair strand is typically class evidence if it lacks a root (follicular tag), as its microscopic characteristics can only narrow the source down to a group of individuals. However, if the hair includes the root with follicular tissue attached, it can be a source of nuclear DNA, making it individual evidence.
3. • Blood: A forensic biologist or a serologist in the biology/DNA unit would analyze the blood to determine if it is human and to generate a DNA profile.
   • Shoeprint: A forensic technician in the impression evidence unit would photograph and cast the shoeprint for analysis and comparison.
   • Hair: A trace evidence analyst or a forensic biologist in the microscopy or biology unit would analyze the hair. They would examine its microscopic characteristics and determine if a root is present for DNA analysis.