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Chapter 13
Crime and Accident Reconstruction
Introduction—Objectives
1. Discuss the contributions of various forensic specialists to crime
2.
3.
4.
5.
6.
7.
reconstruction.
Discuss possible motives for crime-scene staging.
Discuss the factors involved in a motor vehicle collision.
Describe the five levels of an accident investigation.
Compare and contrast skid marks and yaw marks.
Explain the importance of the law of conservation of momentum
and law of conservation of energy in accident reconstruction.
Evaluate factors that can lead to incorrect reconstruction.
Introduction—Vocabulary

contact damage—damage to a vehicle caused by contact with an
object or other vehicle

law of conservation of energy—rule that states that energy is
neither created nor destroyed, but it can be converted into different
forms

law of conservation of momentum—rule that states that the
momentum of a system remains unchanged unless a force acts
upon it

reconstruction—in criminal investigations, the process of
recreating the actions and circumstances based on examination
and interpretation of evidence

skid marks—marks left on the roadway by the tires when the
driver of the vehicle applies the brakes suddenly

staging—the intentional altering of a crime scene in order to
disguise what really happened

yaw marks—skid marks in a curved path as a result of an out-ofcontrol skid
© 2012 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a
publicly accessible website, in whole or in part.
Page 1 of 6
How Many Motives for a Murder?

July 4, 1954 Marilyn Sheppard was murdered in her bedroom

Husband, Samuel, became the chief suspect after knowledge of
an affair became known

Samuel was tried and convicted of murder

On appeal, Dr. Kirk reconstructed the crime scene to prove that a
third person was there

Conviction overturned
Introduction

Reconstruction—the process of reproducing the actions and
circumstances of an accident or crime based on examination and
interpretation of evidence.
History (Obj 13.1)

Dr. Hans Gross—authored textbook on systematic methods for
analyzing facts of a criminal case

Dr. Alexandre Lacassagne—advocated combining science with
criminology

Dr. Edmond Locard—exchange principle

Edward Heinrich—forensics requires broad knowledge in many
fields of science

Dr. Paul Kirk—a dissertation described principles of crime
reconstruction
Role of Evidence

Reconstructionists use evidence to:
•
•

Establish a timeline of events and relationships
Connect victims and suspects involved in the crime
Example: shoe tread
•
•
•
•
Size
Shape
Pattern
Depth
© 2012 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a
publicly accessible website, in whole or in part.
Page 2 of 6
Crime-Scene Staging (Obj 13.2)

Reconstructionists must be aware that crimes may have been
staged

Staging—the intentional altering of a crime scene in order to
disguise what really happened.

Making crimes appear to be:
•
•
Suicide
Accident
Accident Investigation (Obj 13.3)
Level 1: Reporting
Level 2: At-the-scene investigation
Level 3: Technical follow-up
Level 4: Accident reconstruction
Level 5: Cause analysis
Reporting (Obj 13.4)

Level One

Collecting basic information
•
•
Facts
No opinions
At-The-Scene Investigation (Obj 13.4, 13.5)

Level Two

Photographs and Measurements
Coefficient of Friction

Coefficient of Friction—a quantitative value, determined through
experimentation that measures the roughness of a surface.
s2 = 255df
s = speed of travel (km/h)
d = distance (length) of skid mark
f = coefficient of friction
Examinations

Was alcohol a factor?

Contact damage—damage on a vehicle made by another object
© 2012 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a
publicly accessible website, in whole or in part.
Page 3 of 6
or vehicle

Equipment failure

Occupant restraints

Maintenance of tires, air pressure, headlights, taillights
Technical Follow-Up (Obj 13.4)

Level Three

Used when a crime has been committed

Prepare a map of the crime site

Interview witnesses

Assess visibility at the site

Evaluate evidence (e.g., paint chips)

Toxicology report

Autopsy report when there’s a fatality
Accident Reconstruction (Obj 13.4, 13.6)

Level Four

Law of conservation of momentum
—rule that states that the momentum of a system remains
unchanged unless a force acts upon it
—energy cannot be created or destroyed, but can be converted
from one form to another
Law of Conservation of Momentum

Work (w)—the amount of energy transferred by a force (F) acting
through a distance (d).
w=Fxd
Newton’s Laws of Motion

First Law—Law of Inertia
a) an object at rest will remain at rest, and
b) an object in motion will remain in motion with a constant velocity
unless some external force acts on the object
© 2012 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a
publicly accessible website, in whole or in part.
Page 4 of 6
Newton’s Laws of Motion

Second Law—expresses the relationships among acceleration
(a), force (f), mass (m)

Third Law—for every action, there is an equal and opposite
reaction
Law of Conservation of Momentum (Obj 13.6)
Momentum (p) = Mass (m) x Velocity (v)
p=mxv
Cause Analysis (Obj 13.4)

Level Five

Experts share in court, based on facts and research, how and why
an accident occurred

Conflicting analyses are possible
Pitfalls of Reconstruction
Chapter Summary

Several forensic investigators contributed to the acceptance of
crime reconstruction as a scientific, logical, and objective process.

Evidence helps crime reconstructionists establish a sequence of
events leading up to the crime as well as relationships between
the scene, the victim, and the suspect.

Forensic investigators and scientists rely on analysis of evidence
as well as witness accounts to recreate or reconstruct a chain of
events.

Staged crime scenes are usually an attempt to cover up a murder
or insurance fraud.

All accidents must be reported at level one, but accidents that
require research and potential litigation require all five levels of
investigation.

Skid marks and yaw marks help investigators determine the speed
at which a vehicle was traveling prior to a collision or accident.
© 2012 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a
publicly accessible website, in whole or in part.
Page 5 of 6

Investigators use the law of conservation of momentum and the
law of conservation of energy to determine initial velocity of the
collided vehicles.

The three main causes of accidents are:
•
•
•

Environmental factors
Human factors
Vehicular malfunction
To ensure the validity of reconstruction
•
avoid flaws in logic
© 2012 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a
publicly accessible website, in whole or in part.
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