criminalistics the crime scene. information from crime scene & physical evidence corpus delecti-...

Criminalistics

The Crime Scene

Information from Crime Scene & Physical Evidence

Corpus Delecti- facts that establish crime occurred

Modus Operandi- perpetrator’s “signature”

Link person to person, object , scene

Prove/disprove witness, victim, suspect statements

ID of suspect- AFIS, CODIS databases

Investigative leads- paint, footwear

Reconstruction- “How it happened”

WHO RESPONDS TO THE SCENE

Detectives Investigating Case

Crime Scene Unit

Evidence Search & Processing

Identification Unit

Photography & Fingerprints

Medical Examiner

Homicides, Suspicious Deaths

Crime Scene Procedures

1. Protect scene

2. Search for physical evidence

3. Document scene- Notes, photos, measurements, sketch

4. Collect & preserve evidence

5. Transport to laboratory

6. Analyze evidence & reconstruct scene

SECURING THE SCENE

Barrier Tape - or other means (vehicles)

Secure all routes of access into scene

Log Book

Restrict entry

Crime Scene Safety

Wear protective clothing and gear

Always use latex or nitrile gloves

Be alert to sharp objects: Knives, syringes, glass, etc.

Don’t reach where you can’t see!!!

Don’t eat, drink, spit or smoke within the scene

Universal Precautions – body fluids Bleach or dispose of equipment contaminated with blood

Supplemental Resources

K-9 Unit Metal Detectors Aviation/ Marine Bureau Emergency Services Lighting

Halogens Alternate Light Source/ UV

EVALUATING THE SCENE

Walk Through

One member of each group

Determine safe areas to walk

Identify important aspects of the scene

Develop a plan of action, initial theory

SCENE DOCUMENTATION - 1

Video Photography – 3D Orientation

Introduction- placard or audio

Start outside scene

Walk through scene

Overall then close-up on important items

Continuous taping; no sound, no editing

SCENE DOCUMENTATION - 2

Still Photography

Work from outside to inside

Overall, midrange, then close-ups (with & without ID tag)

Examination Quality Photos of Impression Evidence

Overlap photos for perspective/context

Document evidence with tags and scale, cones, flags, placards

Photo Log: date, time, roll#, exposure, settings, description of

item

Patterns (“roadmap” w/ references)

Evidence Documentation

Roadmapping Stain Patterns

Photograph overall pattern using a scale of reference

Roadmapping Stain Patterns

Midrange

Close-up

SCENE DOCUMENTATION - 3•Crime Scene Notes

List Pertinent Information

Date, Time, Location

Personnel

Lighting, Weather

Observations-be objectiveItems Recovered:

Location of itemsPhoto taken?Time CollectedTest results, if any

SCENE DOCUMENTATION - 4

•Rough sketch

•Before collecting evidence

•Overhead or side view

•Compass heading

•Legend

•Measurements fm 2 fixed pts.

Coordinate

Baseline

N

north

east

Item

1

2

3

RP 1 RP 2

Baseline Method – Outdoor sketch

20 ft35

ft60 ft

18 ft

28 ft

20 ftTape measure

0 ft

N

RP 1 RP 2

Triangulation Method

N#1

100 ft

64 ft36 ft

Item fm RP1 fm RP

#1 knife 36’ 64’

Total Station

SCENE DOCUMENTATION – 4Finished CAD sketch

Homicide Investigation

CC# 08-246801

30 Campus Ct, Riverhead

RB 02-10-08

Legend

1 Cartridge

2 Bloodstain

3 Cigarette butt

4 Ski mask

5 Beer can

Search Patterns

Line (Strip) Method Large outdoor scenes

Uneven terrain

Uses several searchers

Move at same pace

Mark evidence when

found

Search Patterns

Grid Method

Move back and forth in

parallel lines

When the area has been

covered, switch to

perpendicular direction

Each area viewed twice,

different perspective

Search Patterns

Quadrant/Zone Method

Large outdoor scenes

Divide scene

Diagram quadrants

Collect evidence within the

quadrant

Air crash

Rooms in house

Automobiles

Search Patterns

Spiral Method

Indoor scenes

Start at perimeter or

center

Move in circular pattern

Locating Physical Evidence

Primary Scene- where principal activity occurs ie. body, cartridge casings, ransacked bedroomTarget area, natural or forced entry & exit points

Secondary Scene- associated locationsVehicleBody dumpedDumpster, garbage cansStaging areaStorm drainsPerp’s residenceNeighbor’s yard

Triage processing if evidence may be compromisedTry to locate the Primary Scene ASAP !!!

Locating Physical Evidence

Ceiling- blood, tissue, projectiles Drapes- blood, fibers Trash cans- gloves, weapons Refrigerator- food Toilet- hairs, urine, fingerprints, Missing items- investigative information Location of PE- may be relevant if suspect was resident

or frequented location on previous occasions

Locating Physical Evidence: Bodies

Another type of “Scene”

Document with notes and photography

Sexual Assault Kit, fingernail scrapings

Fibers, hairs, dried stains on body

Gunshot residue

Accelerants, other Trace Evidence

Clothing, personal items

EVIDENCE COLLECTION

Document evidence prior to collection

Package each item separately

Place evidence in container at scene Prevent loss, alteration, contamination!

Mark with identifying #, initials, date Chain of Custody !!!!!!!

Secure the evidence at the time of collection

Chain of Custody

Authenticates the integrity of the evidence Who had the evidence ? When did they have possession of it ?

PROVE IT!

Security Tape

Jane Doe

EVIDENCE COLLECTION

Fingerprint Evidence

Do not obliterate prints

Package loosely in boxes

Handle only unprintable areas

Do not package in plastic bags

EVIDENCE COLLECTION

Biological Evidence

• Paper containers only

• If wet, air dry ASAP

• Collect item with stain, if possible

• Scrape into paper fold

• Collect stains with damp swab

EVIDENCE COLLECTION

Firearms Evidence Assume gun is loaded!

Document location of

ammunition in weapon

Package ammunition

separately Make sure that all

weapons are clear

1

2

34

5

6

EVIDENCE COLLECTION

Trace Evidence Paint - Scrape into paper fold

• Static can cause loss!

Glass - Package to protect:

• Evidence - so it doesn’t break

• Handler - to avoid injury

Knives - Package to contain sharp edges

LEGAL ISSUES

Search Warrant not required

Search of premises for suspect or victim

To prevent immediate destruction of evidence

Consent

Upon arrest, search of person

Reference Standards/Exemplars

Material from KNOWN source is used for comparison to QUESTIONED evidence

GlassPaintCarpetClothingBuccal swab, blood sampleHair