Forensic Science

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Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Isolate and secure the scene  Document the scene  Search for evidence  Collect and package the evidence while maintaining the chain of custody  Submit the evidence for analysis 3

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. A – Assess the crime scene and assist the injured D – Detain the witness(es) A – Arrest the perpetrator P – Protect the crime scene T – Take notes 4

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. 1) Look for signs of life 2) Cordon off the scene (only allow authorized personnel in) 3) Bodies should be certified as “dead” by a medical examiner (ME) before being moved 5

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  A walkthrough is performed by the crime scene investigator, the first officer, and sometimes the lead detective  Record initial observations of who, what, where, when, and how  Make a plan of action 6

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Record the crime scene and potential evidence with  Notes  Photography  Sketches  Videography 7

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Record the following while at the crime scene (details are the key):  Date  Time  Description of the location, weather, and environmental conditions  Description of the crime  Location of the evidence relative to other key points  Names of all people involved  Any other relevant information 8

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Nothing should be moved until photographed  Take photos of the scene and the surroundings  Photograph entrances and exits  Take wide and close-up photos  Use various angles for each piece of evidence  Use a ruler to show size 9

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Draw a rough sketch at the scene (reconstruct it better later)  Include  Date, time, and location  Scale  Recovered items  Important features  Accurate distance measurements of objects (from two fixed points)  A legend for description of items  A compass designating north  Names of investigators, victims, and suspects 10

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. 11

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Narrate the video  Be objective  Record from different perspectives 12

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Triangulation  For each piece of evidence being recorded, use two permanent objects as reference points that are not likely to be moved  The two reference points and the piece of evidence form a triangle, hence the term triangulation  Whatever object you are measuring to or from, use the same spot on the object every time 13

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Rectangular Coordinates – Baseline  The simplest form of the rectangular coordinate system  Using a straight line between two known points, items are measured along the line and then measured perpendicular to the line  Inside or outside of a house, this line can be a straight wall  Outdoor scenes can use a string or long measuring tape as the reference or baseline 14

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Rectangular Coordinates – Grid  Measure the distance of items from two perpendicular baselines  This technique is particularly appropriate in a room with perpendicular walls or outdoors with perpendicular streets 15

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Polar Coordinates  Measure both the distance and the direction (angle) an object is from a known reference point  For example, 40 feet from the edge of the house and 15 degrees east of north 16

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  When searching a crime scene, wear the following, if available, to minimize contamination  Disposable gloves  Masks  Coveralls with a hood  Slippers 17

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Depend on the size and the location of the crime scene and the number of investigators available  Stick to one pattern and one supervisor  Better to collect everything and not need it than fail to collect something and need it later 18

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Spiral – may move inward or outward; best used where there are no physical barriers  Grid – basically a double-line search; effective, but time-consuming  Line (Strip) – best in large, outdoor scenes  Zone (Quadrant) – most effective in houses or buildings; teams are assigned small zones for searching 19

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission. SpiralGrid Strip or Line Quadrant or Zone 20

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Physical evidence must be packaged and collected before time and weather can alter it  Physical evidence – any object that can establish that a crime has been committed or links a crime and the victim or suspect  The Golden Hour – the window of opportunity to collect time-sensitive information or evidence 21

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Each item must be placed in a separate container, and sealed and labeled  The most fragile evidence is collected and packaged first  Different types of evidence require specific or special collection and packaging techniques  The body is the property of the coroner or medical examiner; collection of evidence on the body is done by that department 22

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Containers such as vials, envelopes, plastic bags, paper bags, canisters, and cardboard boxes are good packaging devices  Most items should be placed in a primary container and then in a secondary container  Trace evidence may be placed on a piece of paper which is then folded in a “druggist fold” and placed in a secondary container 23

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Containers should be sealed with tamper proof tape, and dated and initialed  Each package should contain  Date, time, and location  Case number  Agency and collector’s name  Victim’s name(s)  Description of contents  Never package two items from two different sources or locations 24

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  There must be a written record of all people who have had possession of an item of evidence, beginning at the time of collection  Every person who handled or examined the evidence must be accounted for  Chain of Custody should include  Date and time of transfer  Location of transfer  To/From names  Purpose of the transfer 25

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  Crime Scene Investigators can submit evidence for analysis to several national databases based on the type of evidence  Examples include  Automated Fingerprint Identification System (AFIS)  Integrated Automated Fingerprint Identification System (IAFIS)  Combined DNA Index System (CODIS)  Integrated Ballistics Identification System (IBIS)  International Forensic Automotive Paint Data Query (PDQ) 26

Copyright © Texas Education Agency All rights reserved. Images and other multimedia content used with permission.  , Saferstein, Richard. Forensic Science: An Introduction. New Jersey: Pearson Prentice Hall,  , Ball-Deslich, Barbara and John Funkhouser. Forensic Science for High School. 2 nd Edition. Kenall/Hunt,