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AFIS Residues

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					NIBIN &
Residues

           Jennifer Hansen
Early systems 1990’s

 FBI and ATF had competing
 incompatible computer systems
 FBI
   Program called DRUGFIRE
   Images were collected from a video
   camera mounted on a microscope,
   digitized and stored in a database
   Mostly cartridge casings
Early systems 1990’s

 ATF
   IBIS (Integrated Ballistic Identification
   System
   Processed digital microscopic images of
   features found both on expended bullets
   and cartridge casings
In 1999

 ATF and FBI joined teams to create
 NIBIN National Integrated Ballistics
 Information Network
Gunpowder Residues

 Smokeless powder or nitrocellulose
 Unburned and partially burned
 particles of gunpowder in addition to
 smoke are propelled out of the barrel
 toward the target
Distance Determination

 Process of determining the distance
 between the firearm and the target
 based on the distribution of powder
 patterns or spread of shot pattern
Distance determination

 Used to corroborate suicides and self
 defense claims
GSR

 Beneficial if weapon is available to
 test
   Can compare victims clothing to
   samples shot at different distances
 If weapon not available few
 assumptions can be made because of
 the variety available
If target is less than 1 inch away

 Fibers/hair can appear melted from
 the intense heat from the discharge
 Star shaped pattern
12-18 inches away

 Halo deposited around bullet hole
25-35 inches

 Specs of gunpowder visible
More than 3 feet away

 Should see no signs of GSR
Factors affecting these
assumptions
 Barrel Length
 Caliber
 Type of ammunition
 Condition of weapon
Spread out pattern for a 12 gauge
shotgun
 1 inch for each yard of distance
   10 inch pattern= 10 yards away
 Choke= interior constriction placed
 near the end of the muzzle end to
 control shot dispersal
   Greater the choke =narrower the
   shotgun powder and the faster the
   pellets will be moving
Greiss Test

 Chemical test performed to test for
 nitrates from the burning of the
 nitrocellulose
Primer residues on hands

 Firing a firearm also produces
 gunshot residue on hands and
 clothing of shooter.
Shooter also has GSR

 Dermal Nitrate test was first used
   Disfavored now because false positives
   with
     Fertilizers
     Cosmetics
     Cigarettes
     Urine
     Tobacco
Samples also taken with tape lift
Primers use the following
compounds
 Lead Styphnate
 Barium Nitrate
 Antimony sulfide
In addition to tape lift one can..

 Swab a suspects hand and palms
 with a 5% solution of nitric acid
 Front and back of hand are swabbed
 separately with four different swabs
 All 4 swabs and a moistened control
 are sent to the laboratory
The lab is looking for..

 Presence of Barium and Antimony
 Less than 10 micrograms is the usual
 sample size so the analytical
 technique must be sensitive to small
 amounts of substances
Low rate of positive findings

 Residues removed
   Intentionally
   Unintentionally by rubbing or wiping of
   hands
   Normal washing of hands
Some labs refuse to test samples
that….
 Were obtained more than 6 hours
 after the incidence
Suicides lead to the most…

 Positive results because the body is
 not moved after death
SEM Testing

 Scanning Electron Microscope
 Operator can identify GSR by
   Size
   Shape
   Chemical composition
SEM is very time consuming for
operator
 Automated particle search programs
 could improve the SEM’s potential for
 support in the crime lab
SEM
SEM
SEM

 Sends a beam of electrons toward the
 specimen and then the electron
 emissions from specimen are studied
 Hot tungsten filament used
SEM

 High magnification
   10x-100,000x
 Depth of focus 300x of similar
 magnifications
 High resolution
X-ray analyzer attached

 Identifies substances chemical
 composition
Serial Number Restoration

 Serial Numbers are usually stamped
   Onto metal body or frame
   On a plate with hard steel dies
     The dies strike the metals with a force
     allowing each digit to sink to a prescribed
     depth
Serial numbers are removed by

 Grinding
 Rifling
 Punching
Serial numbers can be restored
because
 Metal crystals in the stamped zone
 are placed under permanent strain
 that extends a short distance
 underneath the original numbers
 If the area has been removed or
 impressed with a different pattern
 numbers will not be revealed
Serial Number Restoration
Before testing an area for a serial
number it must be thoroughly cleaned
of all dirt and oil to a mirror like finish
An etching agent (chemical) is applied
to surface with cotton ball
The strained area dissolves faster
than the unaltered metal revealing the
original numbers
Serial number restoration

 Solution used depends on metal
 surface
   Example Steel surface a solution of HCl
   (120ml), copper chloride (90grams), and
   water (100ml) works well.
Collection

 Hollywood technique is with a pencil
   Fingerprints from trigger are not likely
   GSR residues would be removed
 A record of weapon’s hammer and
 safety position are made and
 investigator unloads the gun before
 sending to lab
Collection

 A record of the location of all fired and
 unfired ammunition in the weapon
 and at the scene must be recorded
Collection

 Revolvers must be on the chamber
 with a scratch mark
 Knowledge of cylinder position and
 live vs. used ammunition can help
 recreate a scene where multiple
 gunshots used
Collection

 Each round is packages separately
 with proper chain of custody
 information filled out
 The guns should be tagged with
   Weapon’s serial number
   Make
   Model
   Investigator’s initial and date
Collection

 Semiautomatics
   The magazine would be checked for
   prints
   Each live ammunition left would be
   packaged separately and labeled
Collection

 If firearm is found underwater the gun
 will be transported to lab submerged
 in the same liquid found in to prevent
 rusting
Collection

 To prevent scratching a bullet upon
 removal, investigators break the
 surrounding support material
 Bullets should be scribed at base or
 nose with investigator’s initials
   Use of pillbox or envelope with bullet
   wrapped in tissue paper recommended
Collection

 Investigator must not remove trace
 evidence such as paint or fiber from
 bullet
 Shells must be labeled and packaged
 as well and marked location of where
 found at scene
 Wad from shotgun must be recovered
 if possible
Gunpowder deposits

 Clothing must be packaged
 separately
 If wet it must be allowed to air dry
Tool marks

 Any impression, cut, gouge, or
 abrasion caused by an tool coming in
 contact with another object
Comparing Tool marks

 Indented impressions can be made
 on doors or windows
   Prying action of screwdriver or crowbar
   Size and shape of tool can be identified.
   No individualized information can be
   found
Reconstructing toolmarks

 Even with suspects weapon the
 examiner finds difficulty in
 reconstructing the proper angle and
 force of tool without damaging surface
 of tool
Collecting tool mark evidence

 Photograph
 Silicon casting
 Investigator must not allow suspects
 tool to be placed in tool mark at scene
   It offers cross contamination according
   to Locard’s principle
   Comparison microscope is examiners
   best tool
Shoe, Tire and Fabric Impressions

 Must be photographed
Lifting Impressions

 Electrostatic lifting device
 By using the Electrostatic Dust Print Lifter Kit, prints left in the dust
 of a floor, light soil from a criminal's shoes, or impressions made on
 overlooked areas such as dusty walls or doors can be recovered.
One of the most overlooked forms of physical evidence at the

crime scene is impression evidence   .
   This is largely due to a lack of specific training in
   the proper search, collection and preservation
   techniques and procedures.
Electrostatic Dust Print
Lifter
 consists of a high voltage power supply/control
 unit, a nickel-plated steel ground plane and a
 metalized lifting medium. The electrostatic lifter
 uses only one metalized plastic sheet and a metal
 ground plane. As high voltage is applied to the
 lifting mat, it takes on a negative charge and the
 ground plane becomes positive. Any dust present
 under the mat will take on a positive charge and
 will then be attracted to the negatively charged
 collection mat. A dust print that is transferred to
 the lifting mat will appear as a precise mirror
 image of the original print and lifts made from
 rough-surfaced floor tile or irregular flooring of any
 kind are facilitated using this method.
Shoeprints

 Photographed
 Casting
Class I Dental Stone

 Form of gypsum
 Cast must be allowed to air dry 24-48
 hours before shipped to laboratory
Snow impression wax

 Used for snow prints
   3 light coats of wax interval of 1-2
   minutes between coats
   Allowed to dry up to 10 minutes
   Followed by dental stone method
Blood tracks left by shoes

 Can be enhanced with chemical
 processes
Comparing impressions

 Must have suspects items for
 comparison
 Individualization made only by
 random wear and tear like cuts or
 gouges
 SICAR- developed in England to keep
 track of tread patterns of shoes
Bitemarks

 Can be used to compare suspect to
 victim.
Casting Lab

 Page 241
Bite mark lab

 Take a foam cup
 Make a soft bite impression on two
 opposite sides of the cup
 Do not bite all the way through
 Cut out the impression and label 1
 with your name
 Place other in the middle of the table

				
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