Essential Elements for Establishing
Training and Procedures Manuals
09-22-04 v.1.0
Projectile Path Reconstruction
Essential
Elements
1.0
Objectives /
Introduction
The
objective of the following guidelines is to identify the
essential elements suggested for use in establishing
training and procedure manuals as applied to the
determination of projectile paths from penetration or
impact.
1.1 To
recognize or identify techniques and procedures used in
the identification, reconstruction, and documentation of
projectile paths based on impact marks including
penetrating, perforating, or non-penetrating points of
impact.
1.2
Projectile paths, for the purpose of this document, are
determined from a short segment of the entire trajectory
path.
2.0
Definitions/
Terminology
Standard terminology should be used in the documentation
of projectile path evidence, from sources such as the
Association of Firearms and Tool Mark Examiners (AFTE)
Glossary and the National Rifle Association (NRA) Fact
Book.
2.1
Commonly used terms may include:
2.1.1
Ballistics: Internal, External, Terminal
2.1.2
Bullet wipe
2.1.3
Conical, Concentric, Radial and Rib glass fractures
2.1.4
Deflection
2.1.5
Incident angle, Departure angle
2.1.6
Keyhole
2.1.7
Perforation vs. Penetration
2.1.8
Ricochet, Ricochet angle
2.1.9
Trajectory
Proper equipment should be used and checked for
acceptable accuracy when appropriate.
3.1 Equipment and supplies may include:
3.1.1 String, cord or rope
3.1.2 Probes of various types and sizes
3.1.3 Laser
devices
3.1.4 Distance
measuring devices
3.1.5 Angle measuring devices
3.1.6 Leveling devices
3.1.7 Plumb bob and line
3.1.8 Calculator with scientific functions
3.1.9 Compass
3.1.10 Measuring tapes and scales
3.1.11 Safety equipment
4.0 Concepts
4.1 Projectile paths can be important in determining
the physical origins of gunshots, location of
additional physical evidence and other general crime
scene reconstruction.
4.2 Over relatively short distances, projectile
trajectories can be represented by a straight line
not withstanding deflection or ricochet. Therefore,
readily available aids such as string, probes and
lasers can be used to illustrate or document the
projectile path.
4.3 Points along a path may be delineated by
penetrating, perforating, or non-penetrating points
of impact.
4.4 A projectile path consists of both the line and
direction along which a projectile travels.
4.5 At least two points of reference are generally
needed to establish a path; however, a single hole
may sometimes be used to estimate a path based on
the associated shape, relative dimension, depth
and/or trace deposits.
4.6 Direction of travel can sometimes be determined
from the shape and characteristics of an impact
mark, as well as from bullet material deposition.
4.7 Caution should be used when attempting to
determine the projectile diameter from the hole or
impact.
4.8 The angle of incidence and the angle of
departure can sometimes be estimated using the
physical characteristics of the impact mark, and the
nature of the impacted material and/or projectile.
5.0 Procedures / Methods
5.1 Recognition of marks and holes
Care should be taken to preserve evidence associated
with projectile impacts as well as to avoid damaging
the projectile during collection.
5.1.1 Documentation of visible characteristics
associated with marks and holes
5.1.2 Trace evidence associated with the marks,
holes, or projectiles should be considered
5.1.3 Chemical tests can be used to recognize impact
marks or holes as well as direction of fire, these
tests may include:
5.1.3.1. Copper residue testing, e.g.,
dithiooxamide
5.1.3.2. Lead residue testing; e.g., sodium
rhodizonate
5.1.4 Define coordinate system to
establish a frame of reference
5.2 Path Determination
5.2.1. Probe method – suitable for relatively short
distances
5.2.2. String method – suitable for relatively short
distances
5.2.3. Laser method – effective for distances or
over terrain where string or probes are not
practical
5.3 Angle Determination
Angle determination includes both vertical and
horizontal angles.
5.3.1 Direct measurement can be performed using a
variety of tools
5.3.2 Basic mathematical formulas can be used to
calculate angles where linear dimensions have been
properly documented
5.4 Documentation
A
variety of ways are available to document the
projectile path relative to fixed locations or
relative to evidence items. These may include:
5.4.1 Sketching
5.4.2 Narrative description
5.4.3 Photographic
5.4.4 Audio or video recording
5.4.5 Measurements
5.4.6 Computer Assisted Programs
5.4.7 Computer assisted programs or software
5.5 Additional Factors for Consideration
5.5.1 Proper evidence collection techniques
5.5.2 Trace evidence
5.5.3 Environment e.g., terrain, physical
barriers
6.0
Training / Qualification of Personnel
6.1 Training may include the
following:
6.1.1 Study of published materials and/or general
procedure manuals
6.1.2 Recognition and collection of firearm and
ammunition related evidence
6.1.3 Documentation techniques
6.1.4 Equipment use
6.1.5 Study under the guidance of experienced
mentors/examiners
6.1.6 Evaluation of known projectile paths during
controlled studies
6.1.7 Report writing and testimony preparation
6.1.8 Supervised or assisted crime scene
investigation
6.1.9 Mock casework and testimony presentation
6.1.10 Formal Courses
Projectile Path 9-22-04.v.1.1.doc
