Week 2 - Crime scene

When CSI is required depends on…

• Type of crime - e.g. major and volume crimes will always get CSI

• Situation

• Resources

Major crime

Murder, rape, serious wounding, aggravated burglary

Volume crime

Burglary, vehicle crimes, thefts - crimes that are repeatedly and frequently happening

Primary crime scene

Where the crime took place

Secondary crime scene

Other associated places, these are of equal importance to the primary scene and are analysed in similar ways

What to consider about preservation

• Importance of first opportunity to arrive at crime scene

• Awareness of potential sources of interference with evidence

• Selection of material at the crime scene

• Understanding what has happened/what has been disturbed

• Awareness of visible and latent evidence

Latent evidence

Hidden evidence that the naked eye cannot see, like DNA or evidence that is not immediately noticeable

Selection

Meaning what might be relevant and worth taking? What items and chosen and why? There are no limits to what is evidence, but investigators can only take so much due to resources and expenses, so important to select evidence that has most probative value

Pressures/tensions in decision making

• Response/preservation of life

• Effective/reliable collection of evidence

• Issues of resources

• Economic/efficient collection of material

• Pressures to provide intelligence to inform investigation

Personnel likely to attend a crime scene

• FOA (first officer attending)

• SIO (senior investigation officer)

• CSC (crime scene coordinator)

• CSM (crime scene manager)

• SOCO - (scenes of crime officer)

How crime scene are cordoned

• Inner cordon - where the main forensic examination happens

• Outer cordon - to prevent movement/removal of evidence or its contamination and to stop unauthorised public access, also provides rendezvous point for personnel with crime scene attendance log to specify who/why attending

CAP - common approach path

A designated route used by crime scene investigators to enter and move within a crime scene.

Stepping plates

Raised square plates on the floor that all personnel use to travel through the crime scene without disturbing anything on the ground

Protective clothing

Worn only for the visitation of the crime scene and destroyed afterwards to prevent cross-contamination

Subjective judgements

Judgement might reflect training, experience, personality and motivation

What was the Dror & Hampikiam (2011) study?

17 expert DNA examiners were asked for their interpretation of data and produced inconsistent interpretations. The majority of “context free” experts disagreed with the lab’s pre-trial conclusion, suggesting the extraneous context of the criminal case (in this case, a rape/sexual assault) may have influenced the interpretation of DNA evidence

What do the results of the Dror & Hampikiam (2011) tell us?

That there can be a biasing effect of contextual info in DNA mixture interpretation

What are the implications of the Dror & Hampikiam (2011) study?

• Specific training on bias issues should be implemented

• Best practices should be especially designed to limit contextual influences

• All types of DNA analysis should not be lumped together as the “gold standard” - they still have issues