Impression Evidence: Footwear, Tire, Bite marks and Tool marks Flashcards
2 levels of identification
class characteristics
individual characteristics
what are class characteristics?
items that point to a particular group
example of class characteristics
brand
tread of shoe
shoe size
what are individual characteristics?
items that point exclusively to one item/person
examples of individual characteristics
nicks and imbedded materials in shoe tread
2 types of impression evidence
-2 dimension
-3 dimension
what is 2-dimensional impression evidence?
length and width
examples of 2-dimensional impression evidence
footwear prints, tire tracks
what is 3-dimensional impression evidence?
length, width, and depth
examples of 3-dimensional impression evidence
footwear impressions, tire impressions, bite marks
order of impression documentation
-notes
-photography
-sketch
what is included in the notes section of impression documentation?
record location of impression, direction of travel, weather, substance composition, etc.
what is included in the photography section of impression documentation?
-Overalls- impression located in overall photos
-Midrange- of impression to a fixed and permanent object
-Close-up without scale
-Close-ups with scale- must use tripod, oblique lighting, compass, and take a series___/__several photos from various angles/sides
what is included in the sketch section of impression documentation?
place on sketch and measure distance to impression using baseline or triangulation
why do we need to use light on different areas of the impression evidence?
We want to highlight certain parts of that footwear with laser or light to do comparison photos of foot impression at crime scene and picture
2 processes to lift 2-D footwear prints
-gel lifter
-electrostatic lifter
what is the process of collecting a 2-D footwear print using gel lifter?
Lift with gel lifter- black or white
Photograph with and w/o a scale prior to lifting
May need to black powder dust surface prior to lifting
Submit to lab: gel lifter, photos, and suspect’s shoes
example of 2D footwear print with gel lifter
dust/dirt prints on counter top/floor
what can someone use instead of gel lifter?
tape lift
what type of prints are made with the suspect’s shoes?
ink prints
what do shoes have to have to be to be collected as evidence?
Shoes have to be worn, not fresh off the shelf
what is the process of collecting a 2-D footwear print using electrostatic lifter?
Use Electrostatic Dust Print Lifter
Must photograph with and w/o a scale before lifting
Sheet of __Mylar__ film is placed over print, roller is used to apply pressure, a high-voltage electrode is applied
Creates charge and causes dust to adhere to film
Not permanent, dust will loose adherence photograph shoeprint on film
Store in __dust________ - free box for transport to lab
what to do with shoe print prior to packaging?
Must photograph shoeprint on film prior to packaging
what is dentstone made up of?
calcium sulfate or gypsum
what is the process for collecting 3D footwear impressions?
cast using dentstone/dental stone
-must photograph with and w/o a scale before casting
how to use/make the cast using dentstone/dental stone?
Mix with water until like __pancake_ __batter__(2 pds of casting material and 12 ounces of water), no lumps, no bubbles
Slowly pour in impression, overlap all edges, may use object to guide pouring
At least ___2___ inches thick, use frame, use hair spray
Mark casts with N direction and case info
Let dry for approx. 45 min depending on temp and humidity
tips for using dentstone/dental stone
It can start to harden while pouring
May use hairspray (aquanet) to make a barrier between dentstone and print for substances with sand, hot cocoa, baby powder
order of collecting, packaging, and preservation of footwear impression casts
Dentstone__- calcium sulfate or gypsum
Package cast in cardboard box, mark fragile, let set for another couple hours, add padding to package
Do __NOT_____ remove debris from impression
Submit to Lab: shoeprint cast, photos, and suspect shoes
why should shoes be packaged separately?
To minimize cross-contamination from the cast we took at the crime scene and make sure the shoes do not damage the cast in transport
what to use for footwear impressions in snow? why?
shoe print wax
-the same wax that snowboarders use to help go down hills faster. It provides color for contrast and a barrier from the dentstone
2D example of tire tacks
3D example of tire tracks
-tire tracks on paved garage surface
-tire tracks in sand/dirt
how to process 3D footwear evidence
Use ___Dental Stone____________ to cast 2D and 3D
Must photograph with and w/o a scale before casting
Submit to lab: cast, photos, _tires__ (if possible) if not, ink tires on paper
Must encompass entire rotation of tires (cast/photos/inked)
Upon comparison between an unknown impression and a known standard (shoe/tire), the examiner can reach how many different conclusions?
3 conclusions
what is the first conclusion?
the standard produced the impression
what is the second conclusion?
the standard did not produce the impression
what is the third conclusion?
There are not sufficient corresponding __individual__ characteristics within the impression to determine whether the standard in question made the impression
what happens if there is no suspect shoes/tires?
FBI database to determine brand/manufacture only
where do you find bite mark evidence?
on the suspect
how to document the bite mark evidence?
Notes: location, bruising, position of marks, etc.
Photographs
Overall, midrange, close-up, and close-up with scale (oblique lighting, series of photos from various angles/sides)
ABFO scale
Sketch: Body diagram with measurements
what does the ABFO scale stand for?
Americanh Board of Forensic Odontology Scale
where to swab for saliva?
take a swab and go all the way around the bite mark, into crevices, and try to pick up epithelial cells from the suspect
how can the bite mark be excise from the deceased victim?
if victim is deceased, the ME will cut out bite mark to have comparison ready if need be
what are usually well-defined without bruising?
postmortem bite marks
what are less distinctive, may have to take photos over several days, UV/IR camera
Antemortem bite marks
what does a forensic odontologist do?
examines molds or casts made of suspect/victim’s teeth and performs comparison
definition of definite
to the exclusion of all others
definition of consistent
no features present that will exclude suspect
definition of possible
unable to positively confirm or exclude suspect
definiton of exclusionary
definitely not made by suspect
what is a toolmark?
when two objects come into contact with each other with an amount of force
the ? the object will mark the ? object
harder; softer
the ? is the “tool”
harder
what can be a tool?
Anything can be a tool
Screwdriver going up against the door
types of toolmarks
compression (impression)
sliding (striated)
cutting (sheared or pinched)
what are compression (impressed) toolmarks?
tool used to indent surface
how are compression (impressed) toolmarks produced?
produced by perpendicular forces acting against an object. the tool doe snot move laterally across the object
examples of compression (impressed) toolmarks
punch marks
hammer blows
gripping tools
what are sliding (striated) toolmarks?
tool slides along the surface leaving striations
what are sliding (striated) toolmarks commonly referred to as?
scrape marks
examples of sliding (striated) toolmarks
prybars
screwdrivers
slippage from jawed tools
what are cutting (sheared/pinched) toolmarks?
Sheared:
blades pass _across___________ each other in a cutting action (scissors, tin snips)
Pinched:
blades butt against each other (wire cutters)
how are cutting (sheared/pinched) toolmarks produced?
Produced when an object is caught between two _opposing__ ___forces__ of cutting actions
what is included in toolmark documentation?
notes, photographs, sketch
what photographs should be taken for toolmark documentation?
Overalls- tool marks located in overall photos
Midrange- of tool marks to a fixed and permanent object
Close-up without scale
Close-ups with scale- must use tripod, oblique lighting, macrophotography, and take a __series__/_several__ photos from various angles/sides
why should those specific close-ups be taken?
In order to visualize the various angles and sides, having light held at different places will help illuminate those for us
what measurements would be taken for the sketch?
Measurements from the floor to impression, length and width of impression, get impression from baseline or triangulation points within crime scene, look for trace evidence on tool marks and tool, everything packaged separately
how to collect toolmark?
Collect entire item bearing toolmark, if not possible -use _Mikrosil__ to cast impression
what happens if it is not possible to collect toolmark?
use _Mikrosil__ to cast impression
PVS Extruder Gun
what to never do during the toolmark collection? whyh?
Never insert suspected tool into or onto toolmark. This can damage the microscopic unique markings on the tool and the mark
how to use Mikrosil?
base (large tube) and hardener (small tube)
Spread out equal _lengths__, not equal _amounts___, on a non-porous surface
Mix together thoroughly
Apply to surface
May leave stick in
Allow to dry
Drying time varies due to temperature, humidity, etc.
Carefully remove from surface
Label stick
Package in __rigid__ container (separate from tool)
what is involved in the lab examinations of toolmark evidence?
Compare tool test-marks to impression (cast/photo)
Use a comparison microscope
New tools may not have developed sufficient individual characteristics
what do the test marks use?
use same surface, same motion, same angle, performed on each edge of tool, etc
A toolmark examiner may be able to determine:
Type__ of tool used (class)
_Size__of tool used (class)
Action employed by a tool in its use (class)
Upon comparison between a toolmark and a tool, the examiner can reach how many different conclusions?
3 conclusions
first conclusion of a toolmark and a tool
the tool produced the toolmark
second conclusion
the tool did not produce the toolmark
third conclusion
there are not sufficient correspondong individual characteristics within the toolmark to determine whether the tool in question made the mark
types of toolmark exams
fracture matches
wood exams
number restoration
what is the fracture matches exam?
to associate items such as broken bolts, auto parts, tips of knives and screwdrivers from objects from which they were broken
ex: fractured tools and toolmarks in bones, broken screwdrfiver tip
what is the wood exams?
to associate marks left by tools used to cut them, such as drill bits
example: toolmarks in bone
what is the number restoration exam?
most often obliterated serial numbers
