crime scene investigation and evidence collection

truth vs justice

truth is a simple fact and justice is the process involving judges and juries

forensic linkage triangle

making connections between each

Scene integrity issues

Addition, destruction, movement

five different ways evidence can manifest

Predictable effects, unpredictable effects, transitory effects, relationship, detail details, functional details

predictable effects

changes to the scene that can occur with regularity or rhythm (flies, arriving to the body)

unpredictable effects

Changes that occur unexpectedly or randomly (turning on the lights at a crime scene, weather)

Transitory effects

Fleeting, time and environment will destroy them. Observe, smell, and feel.

Relationship details

Established correlation between objects

functional details

The operation of items and their condition, did the items work

Sequencing

What order the events occurred

timing

Allow us to place the time in the crime in some form of fashion

guidelines for evidence acceptability

Sufficient and scientific using quantitative objective data; reliable, and it's consistent when retested; valid

national academy of science report in 2009

Evidence and evidence testing it needs to be more scientific; formation of SWG

Scientific Working Groups

Comprise of CSI, professors, and forensic scientist. They revised and standardized protocols, recommendations to improve evidence, collection, and testing, lab equipment must be certified.

police officers

First to arrive on the scene, secure the scene

crime scene investigators

Document the scene in detail and collect evidence

detectives

Interview eyewitnesses

medical examiners

Determine manner of death

district attorneys

May be called to determine if warrants are needed

specialists

Forensic scientists

Locards principle of exchange

Whenever two people/objects come into contact with one another physical transfer occurs. Physical evidence cannot be wrong. It cannot perjure itself. It cannot be wholly absent, only human failure to find it, study and understand it can diminish its value.

Three factors determine the extent of the contact

Intensity, duration, nature of the entities. Evidence does not show when the exchange occurred.

Trace evidence.

Small but measurable amounts of physical or biological evidence found at crime scenes (hair, body fluid, glass)

direct evidence (type of evidence)

Evidence that is authentic, supports an alleged case fact. Firsthand observations.

circumstantial evidence

Implies a fact, but does not prove it directly, physical evidence, biological confidence

Class evidence (evidence characterization)

Narrows to a group of persons or things (blood type, shoe type, guns)

individual evidence (evidence characterization)

Narrows an identity to a single person or thing (dna)

the 7 S’s of crime scene investigation

securing the scene (1st priority safety of people, 2nd priority is preservation of evidence)

separate the witnesses (dont let them talk to each other)

scanning the scene (primary vs secondary scene)

seeing the photos

sketching the scene (rough sketch vs final copy)

searching for evidence

securing and collecting evidence

chain of custody

Maintaining the chain of custody is essential

Every person who possess the items must sign the form to track where it has been from recovery to court

evidence analysis

begins in forensic lab or the PD

crime scene reconstruction

involves forming a hypothesis of the sequence of events from before the crime committed through its completion

staged crime scenes

arson, murder, burglary