2.02 Evidence Collection

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Evidence Collection

Once investigators determine which pieces of evidence to collect, they must retrieve and process the evidence in a way that minimizes loss, degradation, or cross-contamination of evidence.

Common Types of Evidence and Collection Procedures

Read about each type of evidence to learn how it is collected, stored, and preserved:

Item of Evidence	Collection	Preservation/Storage
Blood (pooled, not dried)	Absorb blood with sterile gauze or cloth.	Air dried at room temperature and refrigerated or frozen as soon as possible. May become unusable if not preserved by 48 hours.
Blood (dried stain)	Wrap clothing or object in clean paper and tape closed. If it is not possible to bring the item to the lab, the technician will scrape the dried stain with a clean knife or instrument into a clean envelope and then seal it in an evidence container.	Bring to lab for processing.
Saliva	Collect on a sterile swab, gauze, or cotton cloth and allow to air dry.	Place swab, cloth, or gauze in a clean paper bag and seal. Do not store the sample in a plastic container.
Hair	Collect with tweezers or fingers and place in a paper bindle. A paper bindle is clean paper folded and used to contain trace evidence, sometimes included as part of the packaging for collecting trace evidence. See instructions on how to make an envelope bindle and a druggist bindle.	Package in a clean envelope or paper evidence container.
Fibers	Collect with tweezers or fingers and place in a paper bindle. Never put them directly into an envelope, because small fibers are easily misplaced in large envelopes!	Package in a clean envelope or paper evidence container.
Glass	Small pieces of glass can be packaged directly into a paper bindle. Larger pieces of glass should be placed in a box with cotton or tissue to prevent the edges from chipping or breaking off.	Once in bindles, the small glass pieces can be packed in boxes or canisters and labeled. Large pieces of glass should remain in the box originally packed in, sealed, and labeled.
Paint	Collect paint chips found at the scene in separate paper bindles. If paint is found on clothing, roll the clothing in clean paper and seal.	Package in container, seal, and label.
Firearms	Turn safety on and take out magazine (if indicated). Do not take shotguns or rifles apart. Never submit a loaded weapon.	Package in heavy cardboard or wooden box.
Tool Marks	Wrap item with tool marks or portion of item (like part of a door jamb) in paper, seal, and label. If the item is too large or impractical to send to the lab, casts can be made of the tool marks. The casts are not always reliable and may not be very useful.	Package in box or envelope as indicated by size.
Drugs	Put each drug evidence item in separate paper or specialty evidence containers (PCP, for example requires special containers.)	May package in box or larger envelope. Prescription drugs should be left in original container, sealed in an evidence container, and labeled.
Documents	Put into cellophane or plastic envelopes. Do not mark or deface the documents in any way. Charred documents should be placed on top of cotton and placed in a box.	Seal and label package and hand deliver to lab when possible. If mailed, it must be sent through certified or registered mail.
Fingerprints	Fingerprints can be lifted and then sealed and placed in an envelope. Photographed fingerprints should be labeled and scaled in the photo. Larger items should be handled as little as possible (even gloves or clean cloths used to lift the item can smear existing prints). The item should be packed in boxes and secured with string or peg board. Documents with possible fingerprints should be placed in cellophane or manila envelopes, sealed and labeled.	Seal and label packages as indicated by size/type.
Bullets and Cartridge Cases	Wrap bullets in paper and seal.	Package in small boxes or envelopes.

Source: Georgia Virtual Learning (OER)

You can download a copy of this Common Types of Evidence and Collection Procedures table here.

Knowledge Check #1

What is the best way to deliver documents to the lab for analysis?

1. UPS
2. FedEx
3. Hand deliver
4. Certified mail

Answer: c. Hand deliver. Hand delivery is the best option. Certified mail should be used if hand delivery is not possible.

Knowledge Check #2

Which of these needs to be analyzed within 48 hours?

1. Saliva
2. Blood (not dried)
3. Blood (dried)
4. Fingerprints

Answer: b. Blood (not dried). Blood that has not dried should be analyzed or preserved within 48 hours, or it rinks becoming unusable.

Tools of the Trade

View these videos to see some of the tools used to process and collect evidence. Note the tools used to collect evidence from bullet holes, print and impressions, trace evidence, and blood.

Ballistics (Watch from 3:10-3:58)

Open Evidence Collection - Tools in a new tab

Prints and Impressions (Watch 3:58-5:40)

Open Evidence Collection - Tools in a new tab

Trace Evidence (Watch 6:25-7:58)

Open Evidence Collection - Tools in a new tab

Blood (Watch 7:58-end)

Open Evidence Collection - Tools in a new tab

Knowledge Check #3

Match the following tools to the evidence they aid in collecting.

Tool	Evidence
Vacuum with filter	Trajectory of bullets
Metal detector	Impressions such as shoe prints
Rods and lasers	Prints on tile or hard surfaces
Dental stone and frames	Trace evidence
Electrostatic dust print lifter	Bullet casing or jewelry

Answers:

• Rods and lasers - Trajectory of bullets
• Dental stone and frames - Impressions such as shoe prints
• Electrostatic dust print lifter - Prints on tile or hard surfaces
• Vacuum with filter - Trace evidence
• Metal detector - Bullet casings or jewelry

Personal Protective Equipment

During evidence collection, investigators not only want to protect the evidence from contamination but also want to prevent contaminating themselves, especially if body fluids are present. For this reason, investigators wear personal protective equipment (PPE) whenever they are on the scene. Depending on the scene, PPE may include gloves, booties, hair covering, overalls and a mask.

PPE for Evidence Collection

What the video Evidence Collection - Methodology from 4:10-5:24.

Open Evidence Collection - Methodology in a new tab

Why Wear PPE?

The first reason reason investigators wear PPE is to protect themselves.

Crime scene investigators and forensic scientists are at risk for exposure to bloodborne pathogens infectious microorganisms found in human blood that can cause disease.

Bloodborne pathogens include hepatitis B, hepatitis C and human immunodeficiency virus (HIV). These pathogens may be found in human blood as well as body fluids and untreated cell or tissue cultures.

OSHA

The Occupational Safety and Health Administration (OSHA) lists law enforcement enforcement and forensic laboratory personnel among those at risk for exposure to bloodborne pathogens. OSHA sets standards for both employers and employees to follow to prevent on-the-job exposure to infectious materials.

OSHA sets standards for both employers and employees to follow to prevent on-the-job exposure to infectious materials.

A fundamental part of the bloodborne pathogen standard is universal precautions all potentially infectious materials are treated as though they were infected.

• Barrier protection – Gloves, coveralls and shoes covers are worn if contact with infectious materials may occur.
• Glove change – Change gloves often to prevent using the glove to contaminate another surface (such as your writing pen). Remove the gloves in a manner that will not contaminate skin or clothing.
• Eye and face protection – Protect against splashes or spatters by wearing eye protection such as goggles.
• Wash hands – Wash hands after removing goggles and after removing other PPE such as booties or coveralls.
• No eating, drinking, or applying makeup – Avoid putting things in or near your mouth such as food, drink, lipstick or Chapstick when potentially infectious materials are present.
• Clean equipment – Equipment should be decontaminated after use with bleach, alcohol, or other appropriate disinfectant.

Preventing Infection

The American Red Cross Fact Sheet provides additional information on preventing infection. Scroll down to page 3 to see how to properly remove disposable gloves.

Credits

"Evidence Collecting Techniques" from the Forensic Science course by Georgia Virtual Learning (OER) is licensed under CC BY 3.0.