The Crime Scene

Chapter Two

Forensic Science

Physical Evidence

• Any object that can establish a crime has been committed or can link a crime and its victim and its perpetrator

• Investigator must be able to recognize and properly preserve physical evidence at a crime scene

The Crime Scene

• Step 1: Secure and isolate the crime scene to prevent contamination

• Step 2: Record the scene - make lots of notes

• Step 3: Photograph the scene - before it is disturbed

• Step 4: Sketch the crime scene - rough sketch first; then finished sketch incorporating the notes

Value of Physical Evidence

• If the item of physical evidence is found and subsequently associated with a suspect where the suspect had no right to be, then (when identified) the evidence may:

• Establish a suspect's presence at the crime scene.

• Establish probable cause.• Establish proof beyond a reasonable doubt.

Value of Physical Evidence

• Human factor• Physical evidence "can't lie, quit, die, forget,

or get fired”• Testimonial evidence may change or source

may become "nonexistent' between original and court version

• Physical properties• Cannot change• Only interpretation can change or be in error

"Golden Rule" of Crime Scene Management

"Never touch, change, or alter anything until it has been

documented, identified, measured, and photographed . . .

when a body or article has been moved, it can never berestored to its original position.”

Exceptions:(1) If the potential exists that an item of evidence

(weapon) could be used to cause harm/death to someone at the scene.

(2) If the potential exists for an item/evidence to be lost, contaminated or destroyed

"Transient evidence" is that type of short-lived evidence subject to damage or destruction by exposure to the elements.”

"Evidence which changes with the passage of time."

Crime Scene Search as a General Process

• Approach the scene.• Secure and protect the scene.･ To "secure" is to close access･ To "protect" is to deny access.

• Identify, remove, and separate the witnesses from the scene.

• Perform preliminary survey of the scene.• Establish control.• Determine extent of search

Crime Scene Management

• Develop preliminary theory.• Identify evidence.• Begin narrative.• Record narrative description of the scene.

Notes - keep forever.Audiotape - use new tape, maintain tape in chain of custody as evidence, transcribe.Videotape (sight/sound) - "hears all, sees all," disconnect sound.

Photographic record of the scene.

Photograph the scene

in progressive

sequence,

overview to close-up.

First without scale, then

with.

Utilize a flash if

necessary.

SKETCHING THE CRIME SCENE

• Sketch the scene.

• Document true relationship of items, locations and distances.

• Evaluate items with potential evidential value.

CRIME SCENE SEARCH

• Perform detailed search of scene."No stone unturned”

• Record, collect, mark, and preserve evidence.

• Collection of one type may destroy another type.

• Perform final survey of the scene and double-check documentation and thoroughness of search.

Inward Spiral Search Pattern

• The inward spiral search:

• The CSI starts at the perimeter of the scene and works toward the center.

• Spiral patterns are a good method to use when there is only one CSI at the scene.

Outward Spiral Search

• The outward spiral search:

• The CSI starts at the center of scene (or at the body) and works outward.

Parallel Search

• The parallel search:• All of the members

of the CSI team form a line.

• They walk in a straight line, at the same speed, from one end of crime scene to the other.

Grid Search Pattern

• The grid search: • A grid search is

simply two parallel searches, offset by 90 degrees, performed one after the other.

Zone Search Pattern

• The zone search: • In a zone search, the

CSI in charge divides the crime scene into sectors, and each team member takes one sector.

• Team members may then switch sectors and search again to ensure complete coverage.

Are the doors and windows locked or unlocked? Open or shut? Are there signs of forced entry, such as tool marks or broken locks Is the house in good order? If not, does it look like there was a struggle or was the victim just messy?Is there mail lying around? Has it been opened?Is the kitchen in good order? Is there any partially eaten food? Is the table set? If so, for how many people?Are there signs of a party, such as empty glasses or bottles or full ashtrays?r full ashtrays

If there are full ashtrays, what brands of cigarettes present? Are there any lipstick or teeth marks on the butts?Is there anything that seems out of place? A glass with lipstick marks in a man's apartment, or the toilet seat up in a woman's apartment? Is there a couch blocking a doorway?Is there trash in the trash cans? Is there anything out of the ordinary in the trash? Is the trash in the right chronological order according to dates on mail and other papers? If not, someone might have been looking for something in the victim's trash.Do the clocks show the right time?Are the bathroom towels wet? Are the bathroom towels missing? Are there any signs of a cleanup?

If the crime is a shooting, how many shots were fired? The CSI will try to locate the gun, each bullet, each shell casing and each bullet hole.If the crime is a stabbing, is a knife obviously missing from victim's kitchen? If so, the crime may not have been premeditated.Are there any shoe prints on tile, wood or linoleum floors or in the area immediately outside the building?Are there any tire marks in the driveway or in the area around the building?Is there any blood splatter on floors, walls or ceilings?lls or ceilings

Procedures for Evidence Collection

• Physical evidence must be handled and processed in a way that prevents any changes

• Changes to evidence include: contamination, breakage, evaporation, accidental scratching, bending, or loss through improper or careless handling

Evidence Collection • Item should be kept

in as original condition as possible

• Evidence should be submitted as intact as possible

• Each item collected should be bagged separately

• Bloodstains and other biological evidence should be collected in paper bags, manilla envelopes or druggist folds to prevent the growth of mold.

• Stained clothing should be air dried before wrapping

• Charred debris from a fire must be placed in airtight containers

Chain of Custody

• A list of all people who come in contact or in possession of any item of evidence

Medical Examiner/Forensic Pathologist

• Rigor mortis - muscles relax then stiffen occurs between 24-36 hours

• Livor mortis - blood pools closest to the ground when the heart stops beating leaving

• Algor mortis - body temperature drops at a rate of 1-1/2 degrees F per hour until it reaches ambient temperature

Answers basic questions:• Who was the victim?• What injuries are

present?• When did the injuries

occur?• Why and how were the

injures produced?Performs autopsy toestablish cause of deathEstimates TOD (time of

death)

Forensic Anthropologist

• Identification and examination of human skeletal remains

• Bones can reveal sex, approximate age, race,and skeletal injury

• Create facial reconstructions

Ex: Case Study (pages 60-1)

Forensic Entomologist• Examines insects

and their relation to criminal investigation

• Blowflies, bottle flies, house flies, lay eggs, which hatch into maggots, then grow into adult flies

Ex: The number of eggs, maggots &adult flies can determine the approximate TOD and length of decomposition time.