trace evidence

Question 1

what does forensic evidence establish

Answer 1

1. a crime has been committed
2. links between crime scene’s, victim, offender

Question 2

what is trace evidence?

Answer 2

microscopic quantities of material

probative value in a forensic investigation

Question 3

what are the different types of trace evidence?

Answer 3

1. biological (human)
2. physical - biological (non-human)
3. particles, substance, marks/ impressions
4. natural - manufactured materials

Question 4

what is forensic value?

Answer 4

it establishes spatial and temporal linke between persons ans scenes of interest

only human faliure to find, study and understand it can diminish its value

Question 5

what is the process for trace evidence?

Answer 5

transfer –> persistence –> collection–> analysis –> interpretation –> presentation

Question 6

what are the modes of transfer?

Answer 6

Direct v indirect
secondary transfers

Question 6

what are the two types of transfer?

Answer 6

one way - useful for looking at gun residue
two way - more useful than one way, gives us more than one way to get evidence of suspect

Question 7

what is variation in transfer?

Answer 7

it is amount and distrubution of transferred evidence varies.

Question 8

what are the characterisitcs of varation in transfer?

Answer 8

trace material
properties of source/ recipent
environment conditions
force, duration, type of contact

Question 9

what is frequency in trace evidence?

Answer 9

transfer is not a discrete event
pre and post crime transfers

Question 10

what is trace persistance?

Answer 10

temporal dynamics of transferred evidence.

Question 11

what is trace persistance impacted by?

Answer 11

source/ recipient, environment, evidence characteristics, initial transfer, activity

Question 12

what is the importance of evidence dynamic?

Answer 12

needs to be taken into account for the limits to prevent misrepresentation/ missues of evidence

Question 13

what is trace collection include?

Answer 13

scene, lab, person or their possessions
controls samples are important

Question 14

what is trace analysis?

Answer 14

identified via class characteristics (colour, shape, refractive index) aim to establish point of slimarity between samples
absolute identification often not possible –> exlusion

Question 15

what are the physcal characteristics for classifying evidence?

Answer 15

melting point
boiling point
refractive index
absorption and emisson spectra
density
molecular mass
colour
species characteristics

Question 16

what doe non-destructive techniques include

Answer 16

physical and morphological
(microscopy)

Question 17

what does the destructive techniques include.

Answer 17

for further information
chemical e.g. chromatography and mass spectrometry
depends on: amount / value of evidence, type of crime, aims of enquire, resources.

Question 18

what are the three types of microscopy used for trace evidence?

Answer 18

1 stereo microscope
2 compound microscope
3 scanning electron microscope

Question 19

what does interpretation mean in aspects of trace evidence?

Answer 19

it is the comparison and exclusion of samples

physical evidence is circumstantial - there is no certainty

Question 20

what are some examples of trace evidence?

Answer 20

1 paint
2 glass
3 fibres

Question 21

when can paint be found as trace evidence

Answer 21

it can be found in various crimes: Burglary, vandalism, assault, vehicular

Question 22

when can glass be found as trace evidence

Answer 22

Various crime scenes: burglary, vandalism, assault, vehicular

Question 23

when can fibres be found as trace evidence

Answer 23

Smallest unit of textile material
E.g. clothing, carpets, furniture