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Physical Evidence
LEARNING OBJECTIVES
Distinguish between class and individual characteristics.
Contrast known and questioned sources. Describe the basics of taking soil samples. Explain how to cast a shoe impression using
Dental Stone. Summarize the proper way to collect loose paint
chips at a crime scene. Differentiate between radial and concentric
fractures. Explain minutiae. Describe how plastic prints are formed. Summarize dusting for latent prints using
traditional powder.© 2012 McGraw-Hill Higher Education. All rights reserved. 2
LEARNING OBJECTIVES
Identify five circumstances in which forensic odontology can be an asset.
What conclusions are possible from the examination of hair?
Define “touch DNA.” Explain how to locate “hidden blood” at a crime
scene. Describe how to process a revolver found near a
body at a crime scene. Discuss how to collect a tool impression in a
doorframe where a prying-type action was used to gain entry.
Define questioned document.
© 2012 McGraw-Hill Higher Education. All rights reserved. 3
Class Versus Individual Characteristics Class: a group of objects or persons
with characteristic physical evidence common to it Examples include soil and hair
Individual characteristics can be identified as having originated with a particular person or source Establishes individuality Examples include fingerprints and
footprints© 2012 McGraw-Hill Higher Education. All rights reserved. 4
Comparison Samples
Unknown or questioned samples Recovered crime scene sample whose
source is questioned Questioned evidence that may have
been transferred to an offender during the commission of a crime and been taken away by him/her
Evidence from an unknown or questioned source that can be used to link multiple offenses
© 2012 McGraw-Hill Higher Education. All rights reserved. 5
Comparison Samples
Known samples Standard or reference sample Control or blank sample Elimination sample
© 2012 McGraw-Hill Higher Education. All rights reserved. 6
Locating And Handling Soil Evidence Soil evidence is important when the
suspect drives/walks on unpaved areas It is picked up by:
tire treads shoe bottoms pants cuffs
It may also be located in: subject's vehicle articles in a suspect's trunk
© 2012 McGraw-Hill Higher Education. All rights reserved. 7
Preserving Footwear And Tire Prints And Impressions Footwear prints and impressions
should be photographed: As part of the general scene Also photograph with a scale
Dental Stone is used in casting impressions
© 2012 McGraw-Hill Higher Education. All rights reserved. 8
FOOTWEAR IMPRESSIONS
Photographs of footwear impressions at a crime scene Take general crime scene photos showing
the location of the footwear prints. Take photos from directly overhead using
lighting and a tripod. Include a linear scale next to, and on the
same plane as, the footwear prints. Place a label in the area being
photographed to correlate photos with crime scene and photo log records.
© 2012 McGraw-Hill Higher Education. All rights reserved. 9
Collecting Glass And Paint Evidence Paint may be collected from the
suspect's tools or clothing. Paint can often be collected in dried
chips. Glass is a common form of evidence
at burglary scenes. Before any glass fragments are
removed from a glass window it should be photographed.
© 2012 McGraw-Hill Higher Education. All rights reserved. 10
Cloth Fragments & Impressions Fibers are of greater value as
evidence than are rootless hairs. Fibers may be located on the body of
the victim and/or the suspect. Cloth fragments may be found at the
scene of a violent crime. Cloth fragments may also be found
at the suspect's point of approach or exit.
© 2012 McGraw-Hill Higher Education. All rights reserved. 11
Three Broad Categories Of Latent Fingerprints Plastic prints
Created when the fingers touch against some material such as putty
Contaminated/visible prints Formed when the fingers are contaminated
with such things as ink or blood and touch a clean surface
Latent/invisible prints Left on a surface from the small amounts of
body oil and perspiration that are normally found on friction ridges
© 2012 McGraw-Hill Higher Education. All rights reserved. 12
Major Fingerprint Patterns
© 2012 McGraw-Hill Higher Education. All rights reserved. 13
Conditions Affecting The Quality Of Latent Fingerprints The surface on which the print is
deposited The nature of the material
contaminating the fingerprint Any physical or occupational defects
of the person making the print How the object on which the prints
appear was handled The amount of the contamination
© 2012 McGraw-Hill Higher Education. All rights reserved. 14
Methods Of Developing Latent Prints Traditional powders Fluorescent Powders Chemicals Cyanoacrylate of superglue fuming Visualization under:
Laser Alternative light Ultraviolet illumination
© 2012 McGraw-Hill Higher Education. All rights reserved. 15
RUVIS (Reflected Ultraviolet Imaging System) Generic name for a class of lighting and
imaging systems that have been increasingly used in the past several years.
When the UV light strikes an undetected fingerprint on most nonporous surfaces, it is “bounced” back to he RUVIS and the image is intensified.
Prints located in this manner can then be developed and photographed.
© 2012 McGraw-Hill Higher Education. All rights reserved. 16
Locating Prints
Crime Scene Technician This technician is using powder to
develop latent prints Technicians often wear protective
equipment Several points can
be seen
© 2012 McGraw-Hill Higher Education. All rights reserved. (Courtesy Nassau County, New York, Police Department)
17
Portable Superglue Fuming Chamber Easy to use Produces remarkable results Low cost
© 2012 McGraw-Hill Higher Education. All rights reserved. 18
Forensic Dentistry
Forensic odontology is a specialty that relates dental evidence to investigation
Analyses of bite marks had played a major role in many cases
Teeth marks may be left in food, pencils or other items left at crime scenes
Bite marks can help eliminate or identify suspects
© 2012 McGraw-Hill Higher Education. All rights reserved. 19
Dental Comparison
Dental records are very useful in helping to identify unknown persons who have been the victim of fowl play or who have been reported simply missing.
© 2012 McGraw-Hill Higher Education. All rights reserved.
(Courtesy Dr. Richard R. Souviron, D.D.S., ABFO, Chief Forensic Odontologist, Dade County Medical Examiner Department, Miami, Florida)
20
Hair Document by photos, the evidence log, and by diagram
where the hairs were recovered. Do not submit wet hairs to the lab; they should be allowed
to air dry. If they are firmly attached to an object, leave the hairs
intact and submit the object. When visible hairs are not firmly attached to an object or
the object is too large to submit to the lab, carefully remove them with clean tweezers.
If hairs were possibly transferred to the victim’s and/or suspect’s clothing, keep their clothes apart. Package each article of clothing separately and submit to the laboratory separately.
Do not overlook the potential probative value of animal hair; if a victim’s pets were present at the time of the offense, samples should be pulled from them and handled in the usual manner.
© 2012 McGraw-Hill Higher Education. All rights reserved. 21
Identifying And Analyzing Blood Stains If blood at the crime scene is fresh
and relatively uncontaminated, identification is not difficult
If the conditions at a crime scene are otherwise it is more difficult to identify
One preliminary field test involves the use of Hemident
Blood analyses is important because of the value of DNA typing
© 2012 McGraw-Hill Higher Education. All rights reserved. 22
Sources Of DNA Evidence
These are common sources of blood and DNA evidence that investigators need to be aware of in conducting crime scene searches.
© 2012 McGraw-Hill Higher Education. All rights reserved. 23
Firearm Evidence
Determination from firearms evidence lab examinations of firearm evidence may answer the following questions Was this bullet fired from this weapon? What else can be learned from the bullet? What determinations can be made from
cartridge cases? What miscellaneous determinations can be
made by examination of firearms evidence?
© 2012 McGraw-Hill Higher Education. All rights reserved. 24
Bullet Identification
25© 2012 McGraw-Hill Higher Education. All rights reserved.
When a bullet passes through the barrel of a weapon distinctive scratches are caused
These scratches can be compared to bullets fired through firearms in question
Identification is affected by the condition of the gun and of the bullets
Tool Marks
Identify the type of tool that made the mark or impression
Establish the action used to operate the tool Specify the size and other characteristics of
the tool Identify unusual features Establish whether two portions of a tool were
ever commonly joined Establish whether the evidence is suitable for
comparison purposes Determine whether “this” tool could have
made “that” impression or mark.
© 2012 McGraw-Hill Higher Education. All rights reserved. 26
Questioned Documents
Handwriting and handprinting examinations
There are three types of forgery: Traced forgery Simulated forgery Freehand forgery
© 2012 McGraw-Hill Higher Education. All rights reserved. 27
Questioned Documents continued
Photocopier examination Paper examination Age of documents Burned or charred paper Altered or obliterated writing Writing instruments mechanical-impression instruments Typewriting
© 2012 McGraw-Hill Higher Education. All rights reserved. 28