Forensic Science Chapter 2: Crime Scene Evidence and Investigation

secondary crime scene

a location other than where the crime took place, but is in some way related to the crime and where evidence is found

individual evidence

a material that can be related to a single source

chain of custody

a written record of all people who have had possession of an item of evidence

crime scene

any place where evidence may be located to help explain events

direct evidence

evidence that (if true) proves an alleged fact, such as an eyewitness account of a crime

circumstantial evidence

indirect evidence; evidence used to imply a fact but not prove it directly

class evidence

material that comes from a proven or known source

collusion

when witness or suspects create story of what happened at a crime

control sample

material that connects an individual or thing to a group that share similar characteristics

trace evidence

small but measurable amounts of physical or biological material found at a crime scene

district attorney

the elected or appointed official who represents the government in the prosecution of a crime

first responder

the first police officer to arrive at a crime scene

primary crime scene

the location where the crime took place

Locard exchange principle

there is always a cross transfer of evidence between a suspect and victim or locale

police officer

They are the first to arrive at the scene of the crime, secure the scene & direct activities, and are trained in basic techniques in case they need to collect evidence.

gun

Evidence Item that can be classified as Direct, Circumstantial, Physical, Class.

shoe print

Evidence Item that can be classified as Direct, Circumstantial, Individual.

pollen

Evidence Item that can be classified as Direct, Circumstantial, Physical, Biological, Trace.

written confession

Evidence Item that can be classified as Direct, Individual.

saliva

Evidence Item that can be classified as Direct, Circumstantial, Physical, Biological, Trace.

Crime Scene Investigator

They develop a detailed, technical written record based on observations & activities that occur on the crime scene. They also record data, sketch the scene, take photos of crime scene, & document how the crime scene was examined for evidence during investigations.

Medical Examiner

They determine the manner of death (natural, accidental, homicide, suicide, or undetermined).

Detectives

They interview witnesses, CSI's & specialists to obtain evidence that will help them reconstruct the crime scene.

Secure the scene

Make sure all individuals in the area are safe and preserve evidence.

Separate the witnesses

Witnesses must not be allowed to talk to one another. This prevents them from working together to create a story (collusion).

Scan the scene

Scan the scene to see where photos should be taken. The primary and secondary crime scenes must be determined.

See the scene

The Photography Unit takes photos of the overall area and close up photos with and without a measuring ruler.

Sketch the scene

An accurate rough sketch of the crime scene drawn to scale must be made.

Search for evidence

A spiral, grid, linear or quadrant pattern should be walked and location of evidence marked, photographed and sketched.

Secure and collect evidence

All evidence must be properly packaged, sealed and labeled using specific techniques and procedures.

Crime scene sketch

North should be labeled and a scale of distance should be included.

Important objects in sketch

All important objects (weapon and body) should be measured from two immovable landmarks.

Other objects in sketch

Any other objects in the vicinity of the crime should be included in the sketch (ex. Doors, windows, furniture, trees, vehicles, etc.).

Additional information in sketch

Also include: Date, time, location, case number, and names (Sketched by and Verified by).

Packaging evidence separately

To prevent contamination and mixing.

Biological evidence packaging

Wrapping paper, manila envelopes, paper bags, paper bindle to prevent the growth of mold.

Burnt or charred materials packaging

Airtight containers to prevent evaporation.

Trace evidence packaging

Plastic pill bottles with lids.

Buccal swab

Swab the inside of the cheek.

Factors influencing search patterns

Size of area, number of investigators, type of scene, and type of evidence expected.

Crime scene reconstruction

It is the process of using evidence to build a hypothesis of events (before, during, after the crime).