Deep Dive into Trace Evidence

Locards exchange principle: it is impossible for a criminal to act, especially considering the intensity of a crime, without leaving traces of this presence’ He never actually said ‘every contact leaves a trace’

• it is proxy data • it provides a link between people locations and objects

it aids crime reconstruction: - transfer - where does the trace come from - persistence - when was the trace transferred - activity level - how did it get there?

• never rely on just one piece of evidence e.g. DNA • use lots of trace evidence (it is like a rope and if one strand of rope breaks then the whole chain is fine)

background levels, 10, 20, 30, and 40 transfer

use trace evidence

inceptive - has a crime been committed or not? identification - fingerprints/marks and DNA associative - has contact occurred?

1 - strength of TE is determined by case context and material ‘uniqueness’ 2 - two-way transfer but one of transfers is more obvious than other e.g. additions to scene easier to spot than removals 3 - TE is least understood and most overlooked 4 - non-contact transfer, in addition to primary, secondary and tertiary 5 - absence of evidence doesn’t equal evidence of absence

1 - nature of material 2 - shedding (wool more likely to shed than silk 3 - substrate 4 - nature of contact (pressure) 5 - frequency (similar to amount of time - how many times contact occurred and how long for) 6 - surface area

• as with transfer considerations (nature of material, substrate and nature of contact) but also 1 - emergency services intervention 2 - contamination 3 - post-deposition activity (shower after committing crime) 4 - cleaning/laundering (clean surfaces and wash clothes) 5 - environment/weathering (temp of environment) 6 - animals/microorganisms (unintentional scavengers, bacteria and viruses) 7 - crime to recovery time 8 - recovery to analysis time 9 - trace embedding (fluffy carpet vs wooden floor, embedded in wool vs stuck on wall)

1 - efforts of emergency personnel 2 - scene tampering - CAPs and cordons 3 - not detected (don’t always find everything) 4 - detected but value not recognised - do not see importance 5 - detected and recognised but not relevant to case 6 - overwhelming amount of trace - anything can be evidence 7 - inappropriate collection techniques (loss and damage) 8 - inappropriate storage (loss and degradation) 9 - inaccurate interpretation

1 - recover trace or the entire item? 2 - gloved hand or tweezers? 3 - wet samples? 4 - gelatine lifters (created to lift prints without developing them but will pick up all trace evidence, they are made of collagen and it is a protein so DNA will interfere with collagen e.g. makeup samples) 5 - sequential vs zonal tape lifting 6 - vacuum sweeping 7 - swabbing - not always best for TE 8 - control samples 9 - ESLA (not just for footwear marks, it picks up TE too - the dust that makes up the footwear mark) 10 - hinge lifters (not just for fingermarks - can find drugs of abuse, makeup, glass, paint fragments)

It provides a definition of forensic science and seven fundamental principles

• trace is not something very small or something at the analytical instruments detection limit - can be as large as megalith or as small as GSR particle • traces can be digital now too (a lot of peoples lives are on the internet) • traces are diverse and their detection, recognition, recovery, examination and most if interpretation still relies on human intervention however we make mistakes • CSI and reconstruction are hardest part of FS and shouldn’t be treated same as technical exercise in gathering obvious traces • opinion and interpretation are most important aspects of trace evidence analysis e.g. building materials in builders van = normal but in a car = not normal • we won’t ever really know truth unless person that did it tells us - reconstruction is based on logic, scientific research, traces in front of u and prerequisite knowledge • specific retrodictive model - trying to guess something that happened in past (not predictive model where trying to predict something that will happen in future • context is paramount; background, transfer, persistence and activity. would you expect the number, type and distribution of fibres to be the same if you gave them a gentle hug or hit them?

• TE doesn’t lie, have an agenda, forget things, succumb to emotion or misinterpret scenarios (it is a mute witness/proxy data.) • traces can provide evidence of association or contact, between people, places and/or objects. (Locards principle) • traces can assist in crime reconstruction, i.e. activity level propositions (the difference between a hug and a fight). • TE provides robust and complementary evidence in casework, akin to pieces of a jigsaw puzzle (rope analogy) • can no longer rely exclusively on DNA evidence as the sensitivity of its analysis means contamination is a problem • TE can provide valuable evidence where DNA and fingermarks presence would be legitimate, e.g. where a crime is committed between inhabitants of the property. • where no matches are revealed on either the DNA or fingerprint databases, traces can provide investigative leads

• are they relevant in the context of the case? • do they “match” or share similar characteristics with anything relating to the suspect? • background levels – how common is the fibre? • must consider 2⁰, 3⁰ and even 4⁰ transfer. • non-contact transfer? • the fibre’s material and shedding likelihood. • the nature (material) of the receiving substrate (garment). • how many fibres were recovered. • the location and surface area of fibre recovery. • any evidence of emergency services intervention? • presence of exogenous material. • any contamination from the scene? • have elimination samples been taken from emergency personnel and excluded as a source? • post-deposition activity by suspect? • attempts at cleaning/laundering? • environmental conditions at an indoor scene. • weather conditions at an outdoor scene. • wild animal interference? Or even household pet? • potential microorganism degradation. • suspect’s dislocated scenes – home, car, work, etc. • time elapsed since crime to recovery. • time elapsed between recovery and analysis. • were fibres embedded or interwoven with the garment? • collection technique – sequential or zonal taping? • storage technique – sealed acetate sheet? • trace (fibre) recovery or whole item submission? • has the garment been dried since discovery? • control samples from victim – background levels.