Class vs Individual Evidence, Forensic Photography, Crime Scene Processing

Individual Evidence

Evidence with characteristics that belong to a single source

Importance of Class Evidence

Narrows down possible suspects, stronger with smaller/rarer groups

Purpose of Forensic Photography (three)

1. Crime scene is not secured forever. Documents location and position of evidence for investigation and court

2. Some evidence can not be physically collected, and can only be photographed.

3. Some evidence can not be preserved, or may be damaged when collected.

Why take picture with ruler?

to show scale

Why take picture with evidence number?

to match pictures and records

Class Evidence

Evidence with characteristics that belong to a group

Importance of Individual Evidence

Demonstrates presence at the crime scene,

Analyzing individual evidence is still subjective to the skill of the CSI to make a match, and the evidence available

Overview Shot

Shows evidence in relation to the whole scene

Mid-range Shot

Shows evidence and nearby objects in detail

Close-Up Shot with Ruler/Number

Shows detailed evidence with size reference and evidence number

Close-Up Shot without Ruler/Number

Shows detailed evidence without obstruction or hidden objects

Why take picture without a ruler and evidence?

to not cover evidence

Different lighting in photography?

Using blue/green light or filter to enhance contrast and reveal detail

Oblique Lighting

Placing a strong light source close to the surface beside an object

Better photographs: film vs. digital

Film photographs are better than digital due to manipulation risks

Necessary elements in every sketch

Case number, date and time, location, arrow indicating north, sketch artist, evidence numbers, key that correlates to evidence number

Things needed in photograph log

Evidence number, time, location, date, camera/camera setting, brief description

Direct evidence

Direct proof of a fact witnessed or heard

Circumstantial evidence

Indirect evidence

t does not prove a fact but gives rise to a logical inference that the fact exists

Police officer in crime scene processing

usually first at a scene, Secures the scene to prevent loss or damage of evidence

CSI

Documents crime scene, collects evidence, sends to lab

medical examiner

present only if there’s body, identifies body and informs next of kin, observe scene + body, autopsy

Detectives

Interview witnesses, investigate crime, find suspect using evidence

Common approach path

Placing plastic plates to preserve evidence while moving

How do csi overcome weather conditions?

Building temporary structures, acting quickly

Importance of being completely covered

Prevents contamination of the crime scene

Clothing for CSI agent at crime scene

Gloves, boots, suit, mask, hood

Steps of processing a crime scene

Secure the scene, walk perimeter looking for points of entry, photograph, sketch, collect evidence to send to lab

Spiral search paths

One person spirals in while the other spirals out in large open spaces

Strip or parallel search

Two officers search starting at opposite ends in smaller indoor areas

Grid search

Two officers conduct search in right-left and up-down directions, outdoor or indoor

Quadrant or zone search

Scene divided into zones, officers assigned to each zone, very small

Sealing an evidence bag

Writing initials and date across the seal to detect tampering

Importance of chain of custody

Links crime scene to courtroom, evidence inadmissible if broken

Trace evidence

any type of evidence occurring in sizes so small that it can be transferred or exchanged between two surfaces without being noticed (hair, fiber, soil)

Paper Bindle

used to collect fragile objects into rigid containers to prevent breakage (trace evidence)

Locard Exchange Principle

perpetrator of a crime will bring something into the crime scene and leave with something from it

Porous Paper Bags

wet or that may contain body fluids (blood, semen, etc.) must be air-dried completely.

paper/cellophane envelopes

documents

What can hair reveal

ethnicity, record of poisons, drugs

what determines time of death?

insects on body, state of decomposition, weather conditiion