Marks and Impressions Flashcards
what are examples of body prints?
finger, lip, ear and foot
what are examples of tool prints?
chisel, hammer, pliers
what are examples of manufactured items that can leave prints?
tyres and shoes
what other types of marks and impressions can be made?
weapons, bullets
what is a positive impression?
An impression where material has been deposited
what san example of a positive impression?
marks in blood
what’s a negative impression?
material is removed
what’s an example of negative impressions?
impressions found in dust
what’s an example of indented impressions ?
where the surface is left deformed
what is an example of indented impressions?
shoe prints in mud, or tool marks
what is damaged based evidence?
identifying manufactured items
traits which enable individualisation
what san example of damage based evidence?
tool marks, shoe prints and tyre prints
what are non damage based evidence?
individual traits acquired naturally and every item is unique
what’s an example of non damage based evidence?
fingerprints, lip prints and ear prints
How do you identify impressions at a crime scene?
white light, UV, polarised light, monochromatic light, argon laser light, fluorescence imaging.
what do you do after you identify impressions?
enhance them
what is chemically enchanting impressions?
addition of reagents to alter the material, defining the mark
what’s an example of chemical enchantment for blood marks or fingerprints ?
treating on paper with ninhydrin or DFO to reveal detail in purple
what is physical enchancement?
physical adhesion of material to make the residue or lifting prints to enhance contrast
what two factors have to be considered when retrieving impressions?
nature of surface and impression
how do you lift fingerprints of a non porous surface?
Dust
cyanoacrylate fuming
wash with MoS2
how to enhance iron coloration in soil?
treat soil with thiocynanate
how to deal with chalky soil prints ?
use bromophenol blue to make the print turn blue
what increases the contrast of oily marks?
iodine vapour
what are 3 methods to lift impressions?
3D - plaster cast
in snow wax spray
2D dust impressions lift onto white gel film
How do you do electrostatic lifting of a shoe impression in dust?
place metabolised black mylar sheet on print charge to 15kV imprint dust on sheet print on sheet with clear cover use oblique lighting
after enchaining a print what should happen?
compare it
what do you need to compare?
Using microscopy find individual traits eg:dents or chips.
How can you classify shoe or tyre prints ?
size, manufacturer/pattern
How can you individualise shoe or tyre prints?
systematic wear traits, cuts or scratches
How do you interpret a shoes print ?
compare make by mark
classify by sole and heel pattern
individualise
what do you need to identify a print ?
a sufficient number of individual traits
what do you need to exclude a print?
key differences or conflicting traits
what are the four stages you need to do to confirm who a print belongs to?
identify
enhance
compare
interpret
