persicoscience.weebly.com · Web viewFiber Make-up Lab Directions: You will be comparing a crime...
Transcript of persicoscience.weebly.com · Web viewFiber Make-up Lab Directions: You will be comparing a crime...
Name: _________________________________________________________ Date: ____________
Fiber Make-up Lab
Directions: You will be comparing a crime scene sample to 5 standard reference samples. Through observation you will have to match and identify which standard reference sample matches the crime scene through microscopic cross sectional views of fibers as well as fiber burn-test analyses.
A crime has been committed and the female victim was found in her apartment with several red fibers left behind. The victim despised the color red and did not own anything that was red.
Below you will view the crime scene fiber.
Crime Scene Fiber: The following is a microscopic and cross-sectional view of the fiber found at a crime scene and on the female victim.
Along with the microscopic examination of the unknown fiber, a fiber-burn test was completed. The results of the burn test are as follows:
Fabric Approaching the flame
In flame Removed from flame
Odor Residue
Unknown No change Ignited like a wick, created dark yellow to orange flame
Continued to burn like a candle wick, until extinguished
Burning paper or leaves type odor
Grayish, fluffy, almost power-like
Use the following standard reference samples of cross sectional view an burn test table to narrow down and identify the type of fiber that was left behind.
Answer Analysis questions.
FABRIC FLAME QUALITY ODOR ASH QUALITY COMMMENTS
WOOL orange color, sputteryburning hair or feathers
blackish, turns to powder when crushed
flame will self-extinguish if flame source is removed, no smoke
SILK burns slowlyburning hair or feathers
grayish, turns to powder when crushed
burns more easily than wool but will self extinguish is flame source removed
COTTON yellow to orange color, steady flame
burning paper or leaves
grayish, fluffy slow burning ember
LINEN yellow to orange color, steady flame
burning paper or leaves
grayish, fluffytakes longer to ignite than cotton, but otherwise very similar
RAYON fast orange flameburning paper or leaves
almost no ashwill continue to burn after flame source removed
POLYESTER orange flame, sputterysweet or fruity smell
hard shiny black bead
black smoke
ACETATE burns and melts, sizzlyacidic or vinegary
hard black beadwill continue to burn after flame source removed
NYLONburns slowly and melts, bluse base and orange tip, no smoke
burning celery
hard grayish or brownish bead
will self extinguish if flame source removed
ACRYLIC burns and melts, white-orange tip, no smoke
acrid black hard crustwill continue to burn after flame source removed
Analysis questions:
1. From the cross-sectional analysis, what fiber most closely resembles the unknown fiber. Describe the characteristics they have in common.
2. From the burn test, what type of fiber is most similar to the unknown fiber taken from the victim? Describe the characteristics they have in common.
3. What overall fiber matched the crime scene fiber? Explain how you were able to identify the unknown fiber.
4. If you were the examiner on the case, list at least two other analyses or examinations you would complete on this fiber.
5. If you were the examiner on this case and you were called to testify about the fiber evidence. How confident are you in your prediction of the type of fiber you identified the unknown to be. Would you say you were 100% confident in your prediction? Why or why not?