Unit 9: Evidence Collection

Question 1

• Ignitable liquid.

Answer 1

Replaces accelerant

Question 2

• Fire debris analysis.

Answer 2

Replaces accelerant or arson analysis

Arson suggest intent

Question 3

Lowest temperature of a liquid at which the
liquid gives off vapors at a sufficient rate to
support a momentary flame across its
surface.

Answer 3

Flash Point

Question 4

Ignitable liquid
includes both flammable
and combustible liquids.

Answer 4

Flammable = < 100 degrees

Combustible = > 100 degrees

Question 5

Until scene is completed

it should be viewed as

Answer 5

“large” piece of evidence

Question 6

The unintended transfer of a material onto

the scene and/or onto evidence collected.

Answer 6

Contamination

Question 7

Locard’s exchange principle

Answer 7

• When two materials come into contact with
one another, there will be a transfer of
each material to the other.

Question 8

Suggested decon procedure for tool

Answer 8

• Rinse tool with strong
stream of water.

• Scrub entire tool
vigorously for 30s in a
1-to-3 part solution of
Simple Green

-to-water.
• Rinse tool completely with water.

• Let dry.

Question 9

IAAI AND NFPA 921 POSITION

ON CANINES

Answer 9

Both endorse the use of ignitable liquid
detection canines for the purposes of
locating and selecting samples.

• A canine alert must be confirmed by the
laboratory.

Question 10

Sample selection

Answer 10

• Location:
– From area of suspected
pour.

– Not from an area of extreme
charring.

• Consider the matrix:
– Porosity.
– Contributions from pyrolysis.

Question 11

Comparison Samples

Answer 11

• What are they?
– Comparison samples identify and may
minimize or eliminate sources of interference
in the analysis process.

• When are they needed?
– Almost always…

Question 12

Comparison samples should be collected when submitting:

Answer 12

–    Carpet and padding.
–    Vinyl flooring.
–    Soil.
–    Wood.
–    Shoes.

Question 13

Fire Debris Packaging

Answer 13

• Vapor tight packaging most important.

• Limit sample handling until after ignitable
liquid extraction.

• Prior processing for prints/DNA/explosives
may affect recovery of ignitable liquids.

Question 14

Paint Cans

Answer 14

• Paint cans are recommended.
– Lined or unlined acceptable.

• Clean and unused.
• No more than two-thirds full.

Question 15

Pros and Cons of Paint cans

Answer 15

Pros:
– Durable.
– Readily available.

• Cons:
– Rapid deterioration (rust) in unlined cans.
– Leakage of vapors (if NOTsealed properly).
–Bulky.

Question 16

3 questions in preservation of evidence

Answer 16

• What am I trying to preserve?
• How can I prevent its loss or damage?

• How can I prevent its contamination and
ensure its integrity?

Question 17

Evidence Containers

Answer 17

• Metal cans.
• Special evidence bags.
• Glass jars and vials.

Question 18

Special Evidence Bags

Answer 18

• Ampac
fire debris bags (tubular).
– Cut from roll to needed size.
– Require heat sealer on two ends.

• Nylon bags.
– Available in various sizes.
– Require high temperature heat sealer.

• May be taped, folded over multiple times,
and re-taped.
•
NO COMMON PLASTIC BAGS!!

Question 19

Soil Samples

Answer 19

• Hydrocarbon-eating microbes.
• Degradation within 24 hours.
• Refrigerate samples quickly.

Always collect comparison sample.

Question 20

Collection of Fluid Samples

Answer 20

Pipette 2 to 4 mills into clean glass vial

Place vial into bag then metal can

Question 21

Alternative method for collecting fluid sample

Answer 21

Alternative method:
– Absorb onto gauze or cotton, and place in
metal can or fire debris evidence bag.
– Submit comparison sample of absorbent.

Question 22

Preservation of liquid containers

Answer 22

• Photograph container.
• Note all manufacturer’s markings:
– Brand.
– Lot.
– Production location.
• Provide information with submission documentation.
• Only submit container if it is nearly empty

Question 23

residues: Evidence from suspect

Answer 23

• Skin is absorbent; however, clothing is much
better.
• If absolutely necessary, swab skin.

Submit unused swab as a comparison sample.

Question 24

Evidence from suspects clothes

Answer 24

• Package each garment individually — even
shoes.
• Package in container that allows for
sufficient headspace.

Question 25

Evidence from devices

Answer 25

•   Remember that the entire device is 
important!
•   Submit device for:
–Prints.
–   DNA.
–   Trace (hairs, fibers, etc.)
–   Toolmarks.
–   Ignitable liquids.

Question 26

IMPROPER PACKAGING

CONTAINERS

Answer 26

•   No paper bags.
•   No plastic or Ziplocbags.
•   No plastic bottles/containers.
•   No used containers.
•   Improper packaging results in leaks and 
evaporation of ignitable liquids!

Question 27

Sealing of Evidence

Answer 27

•   Sealing of evidence:
–   Prevents tampering 
–   Tamper-proof seal required.
--   Evidence tape or heat seal
–   Must seal across entire opening.
–   Initials and date on seal.
–   Case number.
–   Description of evidence.
–   Inventory number and item number.
–   Custom-made inventory labels.

Question 28

Petroleum products are

classified, not identified.

Answer 28

.

Question 29

PACKAGING OF CHEMICAL

INCENDIARIES

Answer 29

• Polyethylene or nylon bag.
• No direct contact with metal.
• Plastic bag may be placed in metal paint can.