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Module 10: Characterization and Evaluation of Fired Projectiles…
Module 10: Characterization and Evaluation of Fired Projectiles
Recovered Bullets and Projectiles
examiners report may include
descriptive information
caliber
construction
possible cartridge types
possible manufacturer
general rifling characteristics
listing of possible firearms that may have produced the general rifling characteristics
evidentiary potential based on individual characteristics present
examination
the following preliminary steps should be addressed prior to any of the case comparisons
review lab protocols, as needed
complete administrative requirements
chain of custody
making of evidence
laboratory case identifiers
examiner identity
quality assurance
follow laboratory safety protocols
determine the presence of trace evidence and follow lab protocol for collection
usually includes the following observations and determinations
bullet weight
composition of bullet
base description
type and position of cannelures
manufacturer/marker
general rifling characteristics
caliber
number of land and groove impressions
direction of twist
width of land and groove impression
bullet design
extraneous marks
physical features
plain lead bullets
jacketed bullets
Characterisitcs
weight
normally measured in grains using a balance
measured caliber/diameter
the diameters of the circle formed by the tops of the lands inside the barrel
composition
solid bullets, bullet jackets, bullet cores, bullet coatings, sabots
jacket type
full metal jacket
encloses the entire bullet, with the exception of the base
semijacketed
partially encloses the bullet with the exception of an exposed soft point or a hollow point
total metal jacket
fully encloses a bullet core
magnetic properties
length
color/finish
armor-piercing, exploding, frangible, incendiary, tracer
base construction
solid base
composed of one material with no jacketing
open base
jacketed bullet with core exposed
jacketed solid base
jacketed bullet with the core enclosed
gas check bullet
composed of a lead bullet with a shallow copper alloy cup fitted to the base
base shape
flat base, stepped recess, concave recess, parabolic concave recess, conical recess, truncated conical recess, concave recess with convex protrusion in the center, convex base, conical convex base, parabolic convex base, truncated base bullet
nose construction
soft point, jacketed hollow point, semijacketed hollow point, metal point (capped)
nose shape
round nose, pointed (spitzer, conical/conoidal), wadcutter, flat nose, semiwadcutter, truncated
Identification Equipment
micrometer
calipers
glass measuring reticule
electronic reticule
digital measuring equipment and software
MP 6 optical projector
machinists scale
Damage and Markings
damaged bullets
there may be retrievable information if all of the following are present
one or more measurable land impression
one or more measurable groove impression
sufficient bullet remains to determine a measured caliber
microscopic marks
the information obtained from these striations goes beyond class characteristics as is
unique to a particular firearm
reproducible shot after shot
identifiable with a specific firearm
there are three possibilities resulting from the evaluation of microscopic marks on fired bullets
microscopic marks are present and sufficient for comparison purposes
microscopic marks are present, but insufficient for comparison purposes
microscopic marks are not present, preluding an identification