Forensic Science Test Study Guide Summary

1. Death: Manner, Mechanism, Cause, and Time

  • Death Definition: Cessation of life; irreversible cessation of blood circulation or brain activity.

  • Moment of Death: The point at which life processes stop (heart stops, organs fail, autolysis begins).

  • Autopsy: Performed to determine the manner, cause, and mechanism of death.

Manner of Death (5 Categories):

  1. Natural: Caused by illness or internal failure (e.g., heart attack, stroke).

  2. Accidental: Unexpected death due to unintentional causes (e.g., drowning, car accident).

  3. Suicidal: Self-inflicted death (e.g., poisoning, gunshot).

  4. Homicidal: Death caused by another person (e.g., shooting, strangulation).

  5. Undetermined: Insufficient evidence to classify the death.

Cause vs. Mechanism of Death

  • Cause of Death: The disease or injury leading to death (e.g., gunshot wound, heart attack).

  • Mechanism of Death: The physiological disruption caused by the cause of death (e.g., exsanguination due to gunshot wound).

2. Vocabulary

  • Autolysis: Breakdown of cells after death due to enzymes.

  • Putrefaction: Bacterial decomposition causing gas buildup and bloating.

  • Livor Mortis: Pooling of blood after death, causing skin discoloration.

  • Rigor Mortis: Muscle stiffening after death.

  • Algor Mortis: Cooling of the body after death.

  • Skeletonization: The final stage of decomposition where only bones remain.

3. Stages of Decomposition

  1. Autolysis (0-2 Days): Cells self-digest, skin blisters, rigor mortis begins.

  2. Bloat (2-5 Days): Gas accumulation causes body swelling, putrefaction begins.

  3. Active Decay (5-10 Days): Significant tissue breakdown, body fluid leakage.

  4. Advanced Decay (Weeks-Months): Loss of soft tissues, leaving bones and hair.

  5. Skeletonization (Months-Years): Full decomposition of organic material.

4. Calculating Rigor Mortis

  • Starts: 2-4 hours postmortem (begins in eyelids, jaw, neck).

  • Peak Rigidity: 12 hours.

  • Disappears: 36-48 hours.

  • Factors Affecting Rigor Mortis:

    • Temperature: Cold slows rigor; heat speeds it up.

    • Activity Before Death: Exercise accelerates rigor.

    • Body Weight: More fat slows rigor due to oxygen storage.

5. Calculating Livor Mortis

  • Begins: 2 hours after death.

  • Fixed: After 8 hours.

  • Uses:

    • Helps determine body position postmortem.

    • Indicates if the body was moved.

6. Calculating Algor Mortis (Body Cooling)

  • Cooling Rate:

    • 1.5°F per hour for the first 12 hours.

    • 0.7°F per hour after 12 hours.

  • Formula: (98.6−currentbodytemperature)÷1.5=hourssincedeath(98.6 - current body temperature) \div 1.5 = hours since death(98.6−currentbodytemperature)÷1.5=hourssincedeath

  • Measured via liver temperature.

  • Environmental factors affect cooling (e.g., warm climate slows cooling).

7. Autopsy Procedure

  • External Examination:

    • Noting injuries, marks, and livor mortis.

    • Checking fingernails for forensic evidence.

  • Internal Examination:

    • Y-Incision: Cutting from shoulders to pubic bone.

    • Removal and weighing of internal organs.

    • Rokitansky Method: Removing all organs at once.

    • Brain Removal: Incision from ear to ear, skull sawn open.

  • Final Steps:

    • Examination of stomach contents for time of death estimation.

    • Organs returned or disposed of based on family wishes.

    • Body is sewn up.