The Crime Scene Chapter 2. Physical Evidence Any and all objects that can establish that a crime has been committed or can provide a link between a crime.

The Crime Scene

Chapter 2

Physical Evidence

• Any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator.

• The recognition of physical evidence is essential to the success of the crime lab.

• Types– Direct (testimonial)

• first-hand observations, confessions, video

– Circumstantial• Indirect evidence can imply a fact but not prove it

– Suspects fingerprints at the scene

Class vs. Individual

• Class evidence– Narrows identity to a group of items of people

• Individual evidence– Narrows identity to a single person or thing

Classification of Evidence

• No amount of expensive, sophisticated lab equipment can salvage the investigation if physical evidence is not recognized and correctly collected and preserved.

• In reality only crimes of a serious nature will require evidence collection

What is a crime scene?

• Primary crime scene—site of the original criminal activity – Ex:site of homicide

• Secondary crime scene—site of any subsequent crime. Can be multiple in number– Ex: Where the body was dumped

• All crime scenes are unique and the boundaries of a crime scene are flexible.

ADAPT

– A Assess the crime scene and assist those hurt (Saving lives is most important)

– D Detain the witness (need these guys for questioning)

– A Arrest the perpetrator (many times they will hang around to admire their handy work)

– P Protect the crime scene (this is where the yellow tape comes in)

– T Take notes (notes are very important especially when the case goes to court)

Securing the Crime Scene

• Anyone who enters the crime scene can alter or change the scene and its evidence

• Access should be limited to crime scene personal and a contamination log should be kept.

• Witnesses are separated to prevent collusion.• Must be guarded 24hrs a day until released• A walk-through should be completed

Walkthrough• Preliminary scene survey

• Mentally reconstruct the crime (this can be changed or adapted)

• Determine the boundaries

• Note any temporary evidence that requires immediate processing or protection

• Make a note of weather conditions and take precautions if necessary

Record the Scene

• To preserve the original state of the scene• The original state will only be available for

a limited amount of time• Tools:

– Photography– Sketches– Videography – Notes

Notes

• Must include a detailed written description of the scene with the locations of where physical evidence was recovered

• Must identify the time physical evidence was recovered, by whom, how, and by whom it was packaged and marked

• Tape-recording and narrating a video tape can be faster than writing.

• At some points notes must be transcribed

Videography

• Done without verbal commentary except for factual info such as date and time

• Should include both general and specific areas

• View of the crime scene from the victim’s point of view

Photography

• Done immediately after videotaping

• Better to take too many than to few

• If an object has been moved it can not be returned to be photographed

Diagram

• Make a diagram or sketch that shows the spatial relationships that a photograph cannot

Search for Evidence

• Depends on the location of the crime

• Evidence searched for depends on the nature of the crime

• Important to note what is missing as well

Uses for Physical Evidence

• Info on modus operandi• Info on corpus delicti • Info used to determine the essential facts of an

investigation• Linking persons, scenes, and objects• Verifying witness statements• ID suspects

– AFIS– CODIS

• ID unknown Substances• Crime Reconstruction

Theories behind searches

• The Linkage Theory– The theory that if investigators can establish

positive links between evidence, the crime scene, and the suspect then the case may be solved

– Ex: Bloody fingerprints on the victim’s wrist and on the door knob would be useful while bloody fingerprints on only the doorknob would be less useful.

Theories behind searches

• Locard’s Theory of Exchange– Transfer evidence is created whenever two

objects come into contact with each other.• Primary transfer---victim bleeding onto floor• Secondary transfer---suspect steps in blood on

the floor and tracks it through the crime scene

Search Patterns

Search Methods

• Line– Lots of people walk side by side across some

large area like a field. • Very easy and works well in outdoor areas• Can be modified into the strip method by dividing

the area into a rectangle which is then divided into strips

Search Methods

• Grid– After the line method has been used the area

is searched perpendicular to the original area so that if the searches were over laid they would form a grid

– Benefit is that two different people search the same area

Search Methods

• Wheel– Viewed as a wagon wheel with spokes. Begin

at the center and move outward– Not useful in large areas because the gaps

between searchers become too great.

• Spiral method– Scene is viewed as a circle. Begin in the

center and spiral out or vice versa

Search Methods• Zone method

– Crime scene is divided into zones. Each zone is searched by an investigator then when finished another investigator searches the zone. Works well indoors

• Link Method– Does not follow a geometric pattern. Works

with the linkage theory. Once an item is found investigators then search for the next logical item. Such as if they find a tool mark then they search for the tool that made it.

Evidence from the victim

• The following should be collected:– Victim’s clothing– Fingernail scrapings– Hair samples– Blood– Hand swabs (gunshot residue)– Bullets from the body– Vaginal and oral swabs (if appropriate)

Collect and Package Evidence

• Must be handled and packaged in a way that prevents any change from taking place between when it is removed from the crime scene and delivered to the crime lab.

Evidence

• Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.

Packaging Evidence

• 1. Choose the right size paper for a bindle.• 2. Place evidence into paper bindle and tape

closed.• 3. Place bindle inside a paper/plastic evidence

bag. Fold bag closed. • 4. Place seal over folded edge.• 5. Collector should write his or her name over

the folder edge.

Let’s Make a Bindle

Bloodstained materials

• Packaging of manila envelopes, paper bags or wrapping papers are used to prevent mold contamination

• Allow to air dry first

Charred Debris

• Sealed in an air tight container to prevent the evaporation of petroleum residues

Chain of Custody

• A list of all persons who came into possession of an item of evidence

• Should be kept to a minimum

Standard/Reference Samples

• Physical Evidence whose origin is known that can be compared with crime scene evidence

• Substrate controls– Uncontaminated surface material close to an

area where physical evidence has been deposited (particularly used in arson investigation and bloodstain analysis)

Legal Considerations

• Fourth Amendment Right• Warrant-less search

– Emergency circumstances– Prevent immediate loss or destruction of

property– Incident of lawful arrest– Consent of parties involved

• However, when time and circumstances permit a search warrant must be obtained

Mincey V. Arizona

• Four day search conducted without a warrant after the death of an undercover officer during a narcotics raid of Mincey’s apartment.

• Mincey released on appeal due to warrantless search

• “No exigent circumstances to justify a warrantless search”.

Michigan v Tyler

• Business destroyed by fire suspected to be arson

• Warrantless searches conducted 4, 7, and 25 days after the fire

• Conviction was overturned.

• Entry due to fire required no warrant but subsequent searches had to follow warrant procedures.