Forensics Lesson: Fiber Analysis in Forensics (updated) — Transcript

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1. 0:00all right welcome back forensic students
2. 0:02we are moving through our Fiers section
3. 0:05of our forensic evidence unit and today
4. 0:07we're focusing on fiber analysis and how
5. 0:10fibers can be useful to a forensic
6. 0:13investigator as always feel free to
7. 0:15pause the video as needed now we have
8. 0:18learned about different types of fibers
9. 0:20and how they're classified so in the
10. 0:22previous lesson we learned that we have
11. 0:25two classifications for fibers we have
12. 0:27natural fibers and synthetic fibers and
13. 0:30we talked about some different
14. 0:31characteristics of each of those today
15. 0:34in this lesson we're going to learn how
16. 0:35investigators use those fibers to solve
17. 0:39crimes now fiber evidence is not one of
18. 0:41the more common pieces of evidence found
19. 0:43at a crime scene but nonetheless it can
20. 0:46be an invaluable tool in helping to
21. 0:48solve crimes so fibers can reveal
22. 0:51critical information about and
23. 0:52connections between suspects and victims
24. 0:55and their environment and fibers can
25. 0:58come from a multitude of different
26. 0:59places so clothing and carpet Furniture
27. 1:03curtains bedding insulation
28. 1:06rope now since fiber evidence isn't
29. 1:09specific to an individual or Source we
30. 1:12classify it as class evidence
31. 1:15furthermore fiber evidence can also be
32. 1:17classified as either biological evidence
33. 1:19or physical evidence but this is
34. 1:21dependent on the type of fiber that's
35. 1:23found so again in the last lesson we
36. 1:25learned that we have synthetic fibers
37. 1:27and natural fibers synthetic fibers are
38. 1:30man-made and so synthetic fibers are
39. 1:32considered physical evidence now natural
40. 1:35fibers since they're derived from plants
41. 1:37animals or minerals these fibers are
42. 1:40going to be classified as biological
43. 1:43evidence when fibers are found at a Chom
44. 1:46scene it's important to be very accurate
45. 1:48in recording the location of the fiber
46. 1:50evidence and there are different ways
47. 1:52that investigators can collect fiber
48. 1:54evidence so some of those ways might be
49. 1:56adhesives or forets which are similar IL
50. 2:00to tweezers even vacuums so
51. 2:03investigators can vacuum a large area in
52. 2:05hopes that they collect fibers that they
53. 2:08can use to analyze fibers can be
54. 2:10collected at crime scenes but they also
55. 2:13can be collected in the laboratory and
56. 2:15even during an
57. 2:18autopsy now the first task in fiber
58. 2:21analysis is to identify the fiber and
59. 2:23its characteristics so essentially an
60. 2:25investigator wants to determine what
61. 2:28type of fiber they're working with and
62. 2:30hopes that they can match it to a source
63. 2:32or a point of origin so next the
64. 2:35investigator is going to attempt to
65. 2:36match that fiber to a suspect or Source
66. 2:39either the suspect's home or car or
67. 2:43clothing and if you'll remember from
68. 2:45unit one we talked about low cards
69. 2:47exchange principle which basically says
70. 2:50every contact leaves a trace and what
71. 2:52that means is if somebody commits a
72. 2:54crime they are likely to leave behind
73. 2:57trace evidence at the crime scene or or
74. 3:00even pick up evidence uh from the crime
75. 3:02scene and so using that principle low
76. 3:05cards exchange principle um this is very
77. 3:08helpful when looking into to fiber
78. 3:10evidence so fibers often fall off and
79. 3:12are picked up during normal activities
80. 3:15uh the same is true of crumb scenes now
81. 3:19very small fibers easily Shed from most
82. 3:21textiles and can become trace evidence
83. 3:25and fiber evaluation can show things
84. 3:27like type of fiber color the possibility
85. 3:30of violence um location of suspects and
86. 3:34ultimately point of
87. 3:37origin now there's different ways that
88. 3:39fibers can be transferred um and so it's
89. 3:42important that you know you can have
90. 3:43direct transfer you can also have
91. 3:45secondary transfer so indirect transfer
92. 3:48of fibers can easily be transferred
93. 3:50directly from a victim to a suspect or
94. 3:53vice versa um so example would be a
95. 3:56jacket fiber from a suspect is
96. 3:59transferred to the body of a
97. 4:01victim now we can take that one step
98. 4:04further and add an additional transfer
99. 4:07um and that would be called a secondary
100. 4:09transfer and in a secondary transfer
101. 4:11fibers are going to be transferred from
102. 4:12a source to a suspect and then to a
103. 4:15victim or maybe from a source to a
104. 4:18victim and then to a suspect so an
105. 4:21example would be carpet fibers from a
106. 4:23suspect's house is transferred to the
107. 4:25suspect who then might transfer those
108. 4:28fibers to a victim or to the victim's
109. 4:33clothing now there are different ways
110. 4:35that fibers are tested um and so
111. 4:38investigators are going to first try to
112. 4:39identify fibrous characteristics by
113. 4:41looking at it under a microscope um
114. 4:44these are not going to be basic
115. 4:45microscopes though these are um pretty
116. 4:47Hightech pieces of equipment that
117. 4:49they're working with but lab analysts
118. 4:51are going to make observations about the
119. 4:52color the texture the diameter the shape
120. 4:56pattern and even the cross-section
121. 4:58appearance of these five
122. 5:00fibers now if there isn't enough fiber
123. 5:03evidence present investigators are going
124. 5:05to use what's called a non-destructive
125. 5:07test um or non-destructive technique to
126. 5:11analyze and view these fibers um so
127. 5:13they'll use something like polarizing
128. 5:15light microscopy or infrared
129. 5:18spectroscopy uh to view those fibers
130. 5:21there are some newer non-destructive
131. 5:23techniques that I listed on the screen
132. 5:25so one of those is MSP that combines
133. 5:27microscopy and um with UV light um and
134. 5:32it that is great for very very small
135. 5:35samples of fibers there's also another
136. 5:38non-destructive test being used it's
137. 5:40newer to the field it's called FTI it
138. 5:43uses wavelengths of light to identify
139. 5:46different molecular groups that are
140. 5:47found within the fiber um microscopy and
141. 5:51spectroscopy were both used in the
142. 5:54Atlanta child murderers case so if
143. 5:56you're in my class we're actually going
144. 5:58to look into that case study um in the
145. 6:01future but if you are not familiar with
146. 6:03that case you might want to look it up
147. 6:04because it's very interesting they used
148. 6:07um these non-destructive methods to uh
149. 6:11identify fibers found at the crime scene
150. 6:13and ultimately match these fibers from
151. 6:15the victims uh to the suspect's
152. 6:20home now if there is enough fiber
153. 6:23evidence present investigators can do
154. 6:24what's called a fiber burn analysis and
155. 6:27now this is a destructive test basically
156. 6:30uh investigators will burn a fiber and
157. 6:33they will note characteristics of the
158. 6:36fiber as it burns they'll use the
159. 6:38dichotomus key to ultimately identify
160. 6:41the fiber so fibers when they burn are
161. 6:44pretty predictable synthetic VI fibers
162. 6:47tend to melt when they approach a flame
163. 6:50uh after they burn after they melt they
164. 6:53solidify when cooled so synthetic fibers
165. 6:56do not form an ash after they burn they
166. 6:59form like a hard plastic um
167. 7:03piece when synthetic fibers burn you
168. 7:06know it because they give off a pretty
169. 7:08strong chemical odor if you've ever
170. 7:10smelled uh like a burning tire that's
171. 7:14the the odor um it's very strong now I
172. 7:18do want to note that the the fiber burn
173. 7:21test is a simple way to identify whether
174. 7:24a f fabric is made from natural or
175. 7:26synthetic fibers however the test is
176. 7:30definitely not foolproof it can be
177. 7:32affected by tons of different things
178. 7:33such as blends of
179. 7:36fibers natural fibers burn in a pretty
180. 7:39predictable way too so these fibers they
181. 7:42don't shrink when they approach a flame
182. 7:44they they catch on fire and they burn
183. 7:46pretty quickly um natural fibers burn to
184. 7:49Ash so when they're finished burning
185. 7:51they create ashes which are brittle uh
186. 7:55they smell like burning wood so when
187. 7:57natural fibers burn it smells like a
188. 8:01campfire if you're not familiar with a
189. 8:03dichotomus key I wanted to show you one
190. 8:06I put this one on the screen if you're
191. 8:08in my class we're actually going to do a
192. 8:09fiber burn analysis lab where I give you
193. 8:12some unknown fibers we're going to catch
194. 8:14them on fire and we're going to use a
195. 8:15dichotomous key to match the burn
196. 8:18characteristics to the identity of the
197. 8:21fiber um but if you're watching this
198. 8:24online and you're not in class um this
199. 8:27is an example of a dichotomus key so you
200. 8:29can see here that we would burn the
201. 8:31fibers and just sort of work through
202. 8:34this key to identify what fiber we are
203. 8:39burning all right that ends our lesson
204. 8:42for those of you that are watching from
205. 8:43home and I will see you in the next
206. 8:45lesson