Lecture 1&2 - Intro Flashcards
What did Edmond Locard say which formulated Locard’s exchange principle?
it is impossible to act, especially considering the intensity of a crime, without leaving traces if this presence.
What other term refers to Trace Evidence?
Proxy Data
What does Proxy Data provide?
links between people and locations or objects
What type of evidence does trace evidence provide?
robust and complimentary evidence
What is a main evidence type used nowadays that is not a form of trace evidence?
DNA
Name 3 things trace evidence can help us do?
aid in reconstructing crimes
give investigative leads
be used as complimentary evidence to further support conclusions
What is trace evidence?
smaller materials that are transferred during committing a crime that can help in forensic investigations
What are the 3 main groups of trace evidence?
inceptive = has a crime been committed
identification = fingermarks and DNA
associative = has a contact occurred
Trace evidence can not be unique but it can be…?
characteristic
In what ways could trace evidence be transferred? (2)
contact transfer (1’)
non contact transfer
2’, 3’ or even 4’ transfer
Absence of evidence doesn’t equal ……
evidence of absence
What type of transfer may be easier to spot in a scene?
an addition compared to a removal
In every case what does the value of the trace evidence rely on?
the context of the case
What factors affect the persistance of trace evidence? (9)
environment temp, scene contamination, evidence tampering, weather conditions, emergency services involvement, water submersion, post deposition activities (e.g having a shower), material type, nature of contact
what might promote evidence degradation? (5)
environment/weathering, animal/microorganism interference, crime to recovery time, recovery time to analysis time, how far the evidence is embedded
what factors affect trace evidence transfer? (8)
material type, shedding of the material (some shed easier than others), pressure of contact, surface area of contact, time of contact, presence of sweat, porosity of materials, frequency (contact time and number of times of contact)
Name some challenges associated with trace evidence (8)
emergency personnel intervention, scene tampering, evidence not found, evidence found but not relevant to the case, evidence found but its value not recognised, too much trace evidence found (don’t know what to prioritise), incorrect storage, incorrect collection method (results in loss or damage), bias (leading to inaccurate interpretation)
Name three things used to avoid crime scene tampering
CAP - common approach path
log books to monitor who is going in and out of a scene
stepping plates
What are some things that need to be thought about when recovering trace evidence? (4)
recover the whole item?
use gloves or tweezers?
is the sample wet or dry?
how should it be stored?
what methods can be used to ‘lift’ trace evidence at a scene?
gelatine lifters, swabbing (wet swabs could interfere with the evidence), tweezers, tape, hinge lifters
what type of evidence are gelatine lifters not the best for?
anything with DNA or proteins because gelatine is made of collagen and they could interact causing issues in the analysis
What substances do fingermarks contain that are classed as trace evidence?
grease, proteins, drugs, cosmetics
what type of trace evidence does ESLA collect?
dust
