University:
John Jay College of Criminal Justice
Course:
PSY 421 | Forensic Social and Experimental Psychology
Academic year:

2019
Views:

354

Pages:

4
Author:

Kristopher Elliott

Weave Pattern Analysis Objectives: By the end of this activity, you will be able to: 1. Compare textiles based on their physical appearance. 2. Identify the weave patterns of textile samples. 3. Apply comparative data to solve a forensic science problem scenario. Prelab question: 1. Do some fibers have more value than others? Explain. (2) Yes, Since fibers are typically distributed and manufactured in large quantities they are mostly considered to be class evidence. However if you were to find a fiber with an origin to a limited number of sources then it would become much more valuable. Materials: Different textile samples Microscope Microscope slides Scenario: Weave patterns can help identify a fabric associated with a crime scene. In this lab, you are investigating an assault, in which the victim tore off a piece of his attacker’s shirt. Five suspects have been taken in for questioning, and a judge has issued a warrant to allow the CSI to look for shirts in the suspects’ homes that might match the torn sleeve obtained during the assault. Your task will be to examine each of the suspects’ shirts and determine if any of the fabrics match the torn piece from the crime scene. Procedure: 1. 2. 3. 4. Obtain different textile samples. Using a microscope, examine and identify the weave pattern of each fabric. Use the attached pictures for help. *NOTE* Look at an individual thread in the warp or weft. Follow that one thread and see where it goes (under one over two, over two under two, etc.) Gently tug on each fabric. Note any difference in stretchability. Record your answers in the data table. Plain weave (tabby) Satin weave Leno weave Twill weave Basket weave Data Table (9) Name of textile Weave pattern Stretchability (no stretch, some stretch, easily stretches) Other characteristics (feel, appearance, etc) Polyester Plain weave No stretch Felt like cloth and was white in color. Rayon Plain weave A tiny bit stretchy Not soft but not rough Nylon Leno weave Not stretchy Feels like a bandaid Cotton Twill weave Not stretchy Feels very tight knit Silk Satin Weave Not stretchy Soft and fuzzy Crime Scene Plain weave Not stretchy Not soft but no rough Conclusion: 1. a. Which fiber matched the crime scene? (2) Polyester b. Which characteristics were most helpful in determining a match. Explain at least two. (4) The weave pattern and whether the fabric happened to be stretchy or not helped to determine a match. This is because I had found two fabrics with a plains weave yet one had a little stretch and the other completely didn’t. When it came down to it the stretchiness really helped. 2. Do you think the fiber match is enough to convict the assailant? Explain your answer. (3) Probably not because polyester happens to be one of the most popular fabric blends in the world. 9 out of 10 times you will probably find that someone is wearing a polyester shirt. 3. You are the accused attacker. Explain how the victim obtained the torn piece of your clothing. (4) 4. What other evidence could be used to convict the attacker of the crime? (4) Hair or plant fibers as scene on CSI could be used to convict the attacker depending on where the setting of it had taken place.

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