Bullet/Cartridge Analysis Flashcards
what are class characteristics of a bullet
land/grooves impressions (number, depth, width)
twist direction, caliber, shape
class characteristics of bullet casing
shape, manufacturer, caliber, composition, extractor/ejector marks, breech face and firing pin
what is caliber
approximation of diameter of the bullet
what kind of evidence can you pull form a damaaged bullet
DNA and GSR
what is a mushroomed bullet
a bullet desgined to expand on impact causing the target more damage
what might you need to do to analyze a mushroomed bullet
carefully adjust the bullet shape to look for things
what to look for with lands/groove marks
number of lands/groove, measurable lands/grooves, measurement of imporessions
what is so different about glocks
they have rounded lands/grooves ie polygonal (0 in measurements)
what are adaptors and what are they used for
adaptors are stuck int he barrel to help smaller bullets travel down the barrel easier
are adaptors riflied
they may or may not be
what are subclass characteristics
where the tools to make items and worn/damaged and the mark is left on the tool is it making
what are individual characteristics
they are marks accidentally left by when a tool is used they are unique and a little special
what bullet striations
individualizing marks on bullet they are unique to each firearm
shawing/shearing
a bullet being cut form a misaligned revolver barrel
skid marks:
smudgy rifling being the bullet gets caught and actually gets rifling
what are striated action marks and what are some examples
they are microscopic scratches on the case. some exmples are firing pin drag, extractor and ejector marks
what is a chamber mark
it is when the explosion int he case causes the case to expand and take the impression of the firing chamber
how can you determine if a bullet was shot by a glock
by checking for a square firing pin mark in the breech face (hot cartilage into square pin then impression left)
what are impressed action marks and what are some examples
they are marks impressed by a hard hitting object (hammer like movement) some examples are firing pin and breech face marks
How to ID a shotgun
best bet is finding the shell and looking for marks there
how do you compare lab samples
you compare known and unknown
how can you obtain the known samples
water tank: possible damage when collected
bullet catcher: non-flammable fiber, undamaged bullets
indoor firing range: to test for GSR, no bullet recovery
what is the cibin database
the Canadian integrated ballistic identification system, compares bullet info across the country and NIBIN
Comparison conlusions part 1
- no value: no visible evidence of bullet, nothing to properly analyze
- of value: has enough evidence to analyze
comparison conclusions part 2
- exclusion: class characteristics don’t match
- insufficient support for exclusion: class matches but individual don’t match
- insufficient support for either: class matches but not enough KNM
- insufficient support for ID: class match and most individual match’s
- ID: class match and ALL individuals match
what might be hard about guns in a cold case
damage and wear+tear in the gun over time changing the striations
