Forensics Evidence Collection and Preservation

Crime Scene Investigation

The meeting point of science, logic, and law.

“Processing a crime scene”

A long, tedious process involving purposeful documentation of the conditions at the scene and the collection of any physical evidence that could possibly illuminate what happened and who did it.

Crime Scene

A location where a crime took place

Evidence

Anything presented in support of an assertion

Circumstantial evidence, Indirect evidence

Trace evidence, requires that a judge and/or jury make an indirect judgement/inference about what happened, more reliable

Physical evidence or biological evidence

Class evidence or individualistic evidence

Direct evidence

First hand accounts, testimony by a witness about what the witness saw, heard, or did, video recordings of the crime, may or may not be reliable

Physical evidence

Any tangible item that can be collected and analyzed to prove a fact or link a person to a crime. Examples: Weapons, fingerprints, fibers, and documents. Key Characteristics: Tangible objects that can be observed and held. Preservation: Requires careful documentation and storage to prevent contamination. Role in Investigation: Can be used to determine how a crime was committed, identify a suspect, or clear an innocent person.

Biological Evidence

A subcategory of physical evidence that originates from a living being and is analyzed for its DNA. Examples: Blood, saliva, semen, hair, tissue, and bone. Key Characteristics: Often microscopic and may not be visible to the naked eye. Preservation: Must be stored in conditions that prevent degradation, such as refrigerated or temperature-controlled environments. Role in Investigation: Provides a unique identifier for an individual through DNA analysis.

1.) Identify evidence

Placards are placed by evidence as it is found. Investigators look for evidence in a systematic way.

Spiral search method, grid method, strip/line search, quadrant/zone search

2.) Photographing Crime Scenes

Photographs allow a visual permanent record of the crime scene and of items of evidence collected

Photographs should be taken ASAP, 3 positions: overall scene, mid-range photographs, close up

1. Photograph entire area before entering

2. Photograph victims, crowds, vehicles

3. Photograph entire scene with overall, medium, and close up coverage-use measurement scale when appropriate and make sure that the photos are taken at 90 degree angle (close up one time)

4. Photograph major evidence items before they are moved

5. Photograph all latent fingerprints and other impression evidence before lifting and casting are accomplished

6. Prepare photographic log and photographic sketch

Preservation of Evidence

From the crime scene, all evidence must be inventoried and secured to preserve its integrity to the court room

Collecting evidence

Each type of evidence may have a specific way to be collected and packaged. Each piece of evidence must be placed in a separate bag or container and labeled with date, time, location, and collector. Biological samples that are susceptible to bacterial or fungal contamination should not be kept in an airtight container.

For all evidence

photograph first, consider proper method of collection, fill out evidence collection bag/envelope for the evidence, add the evidence to the evidence log, put on fresh gloves, collect the evidence and place in the evidence bag, seal the evidence bag, sign and date the seal.

Dry, solid trace samples

Use tweezers, vacuum, scraping, combing, clipping, tape lifting. Add evidence to bindle. Examples: hairs, fibers, particles of soil, particles of glass, broken nail. Evidence should be packaged separately into paper envelope/small evidence bag and sealed. Fingernail scrapings-collect with dull pick much like toothpicks.

Dry, solid larger samples

Pick up, cut out, etc. - be careful where you are grabbing the item. examples: soda can, small carpet, document/letter. Evidence should be packaged separately into paper/small evidence bag and sealed. If sharp, the blade should be wrapped in stiff unmovable cardboard before being placed in the bag (the evidence should be labeled so that people know the contents are sharp).

Wet samples, biological.

Handle with extreme care. Swab-you must allow the swab to dry to prevent mold/bacteria and sample degradation. If it cannot be allowed to dry at the scene, it can be packaged in plastic to prevent cross contamination for no more than 2 hours and then allowed to dry in a safe location. Examples: wet blood, wet saliva, wet semen. Once swab is dry, it can be packaged in a paper bindle and then placed in a paper envelope labeled as biohazard. Entire item can be collected and swabbed at the lab (blood soaked shirt - entire shirt can be packaged, blood drops on carpet - carpet may be cut out and brought to lab). If biological sample is found at the crime scene already dry, you can take the entire item. If the item cannot be taken, the sample can be swabbed using a dampened swab with distilled water) and then allowed to dry as specified earlier.

Dry samples, biological.

• HANDLE WITH EXTREME CARE • TAKE THE ENTIRE ITEM IF POSSIBLE. PLACE IN A PAPER ENVELOPE LABELLED AS BIOHAZARD. • IF SAMPLE IS ON A NONPOROUS SURFACE, SCRAPING THE SAMPLE OFF MAY BE AN OPTION. PLACE THE DRIED SAMPLE IN A BINDLE AND PLACE IN AN ENVELOPE. • IF THE ITEM CANNOT BE TAKEN, THE SAMPLE CAN BE SWABBED USING A DAMPENED SWAB (WITH DISTILLED WATER) AND THEN ALLOWED TO DRY AS IF IT WERE A WET SAMPLE

Firearms

• BULLETS AND CARTRIDGE CASING CAN BE COLLECTED AS TRACE EVIDENCE WOULD BE. THE OUTSIDE OF CARTRIDGE CASES SHOULDN’T BE TOUCHED SINCE IT COULD CONTAIN FINGERPRINTS • WHEN FIREARMS ARE FOUND AT THE CRIME SCENE, SAFETY IS MOST IMPORTANT • PICK UP BY TEXTURED GRIP OF THE HANDLE • MAKE SURE THE BARREL IS NEVER POINTED TOWARD PEOPLE • UNLOAD THE WEAPON • TAKE NOTES ON THE CONDITION OF FIREARM WHEN FOUND AND STEPS TAKEN TO RENDER IT SAFE WITHOUT DESTROYING EVIDENCE • FIREARM CAN BE PLACED IN A PAPER BAG OR ENVELOPE SEPARATE FROM AMMUNITION OR MAGAZINE • FINGERPRINTING MAY OCCUR AT THE LAB

Impression evidence.

• CAST THE IMPRESSION IF IT IS NOT PERMANENT (IE

IN SOIL OR SNOW) – THE TYPE OF CAST WILL

DEPEND ON THE MATERIAL

• THE IMPRESSION CAN BE COLLECTED IF IT IS

PERMANENT

• EXAMPLES: SHOE IMPRESSION, TIRE IMPRESSION,

TOOLMARKS, BITEMARKS.

Arson evidence

• ASH AND SOOT ARE COLLECTED IN NEW, CLEAN PAINT CANS

• MATERIALS SHOULD BE COLLECTED FROM DIFFERENT AREAS WITH PARTICULAR ATTENTION PAID AT THE POINT OF ORIGIN AND PLACED IN A SEPARATE CAN FOR EACH AREA

• ANY ITEMS THAT MAY CONTAIN FLAMMABLE RESIDUES SHOULD BE COLLECTED IN PAINT CANS

• MANY FLAMMABLE SUBSTANCES ARE VOLATILE (EVAPORATE

EASILY) – SEALED PAINT CANS ARE INEXPENSIVE, AIRTIGHT, AND

UNBREAKABLE

• CANS SHOULD BE PACKED ONLY ONE HALF TO TWO THIRDS FULL TO LEAVE ROOM FOR VOLATILE GASES TO COLLECT (AND ULTIMATELY BE MEASURED)

• PLASTIC BAGS CAN REACT WITH VOLATILE COMPOUNDS FROM

FLAMMABLE SUBSTANCES

Standard/Reference Samples

• PHYSICAL EVIDENCE WHOSE ORIGIN IS KNOWN SUCH AS BLOOD, HAIR, GLASS OR SOIL

FROM A SUSPECT THAT CAN BE COMPARED TO THE CRIME SCENE EVIDENCE

• EXAMPLES

• SOIL SAMPLES FROM ALL TYPES OF SOIL AROUND THE CRIME SCENE

• BLOOD SAMPLES FROM THE VICTIM AND THE SUSPECT

• SAMPLES OF ALL MEDICATIONS FOUND AT THE CRIME SCENE

• HAIR SAMPLES FROM ALL PERSONS AT THE SCENE

• FINGERPRINTS FROM PEOPLE EXPECTED TO BE AT THE LOCATION

Control samples

A SAMPLE OF CHARRED CARPET IS THOUGHT TO HAVE ACCELERANT RESIDUE ON IT

IT IS COMPARED TO THE SAME KIND OF CARPET KNOWN TO BE FREE OF THE SUSPECTED MATERIALS.

A CARPET SAMPLE TAKEN FROM AN UNDAMAGED SECTION OF FIRE MAY PROVIDE THE KNOWN SAMPLE.

IF A SUSPICIOUS CHEMICAL IS PRESENT IN THE CHARRED CARPET BUT NOT IN THE KNOWN SAMPLE, THE LAB CAN BE MORE CERTAIN THAT THERE IS A FOREIGN CHEMICAL INVOLVED AND NOT A COMPONENT OF THE CARPET OR ADHESIVE

Evidence collection on deceased

AUTOPSIES ARE PERFORMED ON DECEASED VICTIMS WHEN DEATH IS UNEXPECTED OR SUSPICIOUS

• THE MEDICAL EXAMINER MUST GET ALL OF THE EVIDENCE OFF OF THE BODY BEFORE IT IS BURIED OR RISK LOSING IT

• EVIDENCE SUCH AS THE FOLLOWING MUST BE COLLECTED

• CLOTHING

• FINGERNAIL SCRAPINGS

• BLOOD

• DNA

• ONCE A BODY IS BURIED, GETTING EVIDENCE OFF OF IT TAKES TIME AND HAS TO GO THROUGH THE COURT SYSTEM (EXHUMATION)

Computer crimes evidence

• SEIZURE OF DEVICES CONTAINING ELECTRONIC EVIDENCE:

• CELLULAR TELEPHONES

• COMPUTERS

• MEDIA PLAYERS SUCH AS IPODS OR (PURCHASED MP3 PLAYER

FROM STORE ARE APPROVED.)

• CORRECTIONS STAFF SEIZING ELECTRONIC EVIDENCE SHOULD HANDLE EVIDENCE AS LITTLE AS POSSIBLE AND UNDER NO CIRCUMSTANCES SHOULD STAFF TURN THESE DEVICES ON OR ATTEMPT TO EXTRACT INFORMATION FORM THEM.

• THEY SHOULD BE HANDLED LIKE ANY OTHER EVIDENCE AND THEN TURNED OVER TO THE DIGITAL ANALYST

Chain of custody

• THE CHAIN OF CUSTODY BEGINS WHEN THE ITEM IS COLLECTED.

• ANY TIME EVIDENCE IS TURNED OVER FROM ONE PERSON TO ANOTHER, THE PERSON RECEIVING IT SHALL SIGN FOR IT BEFORE TAKING POSSESSION.

• USED IN COURT TO ACCOUNT FOR THE WHEREABOUTS OF EVIDENCE SINCE COLLECTION

• IF CHAIN OF CUSTODY IS BROKEN, THE INTEGRITY OF THE EVIDENCE COMES INTO QUESTION

• MAKE SURE YOUR INFORMATION IS ACCURATE

• INFORMATION MUST BE CONSISTENT ON ALL PAPERWORK; WHO, WHAT, WHEN, WHERE, ETC..

• DO NOT USE GENERIC TERMS WHEN DESCRIBING EVIDENCE (I.E. SHANK, ETC.)

• BE AS SPECIFIC AS POSSIBLE TO DESCRIBE ITEM

• DON’T MAKE ASSUMPTIONS, REPORT FACTS

• MUST LIST ALL OF THE PERSONS WHO COME IN CONTACT OR POSSESSION OF AN ITEM OF EVIDENCE

• ALL EVIDENCE MUST BE SECURED IN EVIDENCE LOCKER

THE CHAIN OF CUSTODY REQUIRES THREE TYPES OF TESTIMONY:

1. TESTIMONY THAT A PIECE OF EVIDENCE IS WHAT IT PURPORTS TO BE

2. TESTIMONY OF CONTINUOUS POSSESSION BY EACH INDIVIDUAL

3. TESTIMONY BY EACH PERSON WHO HAD POSSESSION THAT THE PARTICULAR PIECE OF EVIDENCE REMAINED IN SUBSTANTIALLY THE SAME CONDITION FROM POSSESSION OF ONE PERSON TO ANOTHER

Packaging

ALL PACKAGES SHOULD CONTAIN THE FOLLOWING INFORMATION:

1. DESCRIPTION OF THE ITEM – USE GENERIC TERMS, NOT JAIL LINGO LIKE “SHANK”

2. WHERE IT WAS FOUND

3. PERSON’S NAME AND NUMBER (IF APPLICABLE)

4. DATE AND TIME FOUND

5. NAME OF STAFF SEIZING THE ITEM

PAPERWORK ATTACHED TO PACKAGING IS NOT ENOUGH!!