Assignment 3.docx - Unit 5 CSI Crime Scene Investigation...

Unit 5 CSI
Crime Scene Investigation Assignment 5
Marlena Perkins
Crime Scene Investigation, Post University
CRJ 342_30, Prof. Dyer
November 27, 2022

Unit 5 CSI
1. You are the investigator assigned to collect evidence from a suspected arson.
Describe how you would collect evidence containing ignitable fluids.
As the investigator assigned to collecting evidence from a suspected arson, the evidence
containing ignitable fluids requires special care. Searching for the container is important as it
may contain fingerprints or other DNA evidence linking the suspect to the crime. It is suggested
to search for evidence by looking for items out of place, if a container is found, begin the search
from there. The search for evidence should be focused on finding the ignition device such as a
matchbook or lighter. Liquid residue samples are likely to be found at the point of origin,
however, searching in the pour pattern can produce the best evidence samples. The lowest areas
with insulation, porous plastic or manmade fibers, cloth and cardboard, seams, tears and cracks,
edges of the burn patterns, and floor drains or base walls are high evidence areas. Tools must be
cleaned before and after collecting evidence to avoid cross-contamination. Tools with steel
blades, such as shovels, hoes, trowels, and chisels, are the recommended tool of choice when
collecting ignitable liquid evidence. Like a paint can, one-quart and one-gallon evidence cans
store residue samples best. As with most evidence, photographing the pour pattern before taking
a sample, is necessary. Liquids tend to pool in low areas, so be sure to keep that in mind when
searching for evidence to collect. When collecting the evidence wearing gloves is common
practice, remove debris, and place the debris samples inside the evidence container leaving one-
third of the can empty. The one-third of the space left in the evidence container is called
“headspace” and is where the vapors from the collected debris will gather, these vapors are what
the lab will test. The evidence label needs to be placed on the side of the container, as lids are
sometimes removed and replaced (InterFIRE Resource Center, n.d.). Labels should include the
location where evidence was found, the date and time of evidence collection, and the name or

Unit 5 CSI
initials of the person collecting the samples. Finally, it is recommended to heat seal the bags to
avoid holes or gaps in the seal (California Department of Justice, Bureau of Forensic Services,
2018).