1. Physical Evidence
Chapter 4

2. 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.
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3. 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.
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4. 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
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5. 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
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6. Comparison Samples Known samples Standard or reference sample
Control or blank sample
Elimination sample
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7. 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
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8. 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
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9. 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.
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10. 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.
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11. 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.
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12. 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
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13. Major Fingerprint Patterns
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14. 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
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15. Methods Of Developing Latent Prints
Traditional powders
Fluorescent Powders
Chemicals
Cyanoacrylate of superglue fuming
Visualization under:
Laser
Alternative light
Ultraviolet illumination
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16. 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.
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17. Locating Prints Crime Scene Technician
This technician is using powder to develop latent prints
Technicians often wear protective equipment
Several points can be seen
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(Courtesy Nassau County, New York, Police Department)

18. Portable Superglue Fuming Chamber
Easy to use
Produces remarkable results
Low cost
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19. 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
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20. 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.
(Courtesy Dr. Richard R. Souviron, D.D.S., ABFO, Chief Forensic Odontologist, Dade County Medical Examiner Department, Miami, Florida)
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21. 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.
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22. 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
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23. 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.
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24. 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?
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25. Bullet Identification
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
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26. 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.
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27. Questioned Documents Handwriting and handprinting examinations
There are three types of forgery:
Traced forgery
Simulated forgery
Freehand forgery
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28. Questioned Documents continued
Photocopier examination
Paper examination
Age of documents
Burned or charred paper
Altered or obliterated writing
Writing instruments
mechanical-impression instruments
Typewriting
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