Physical Evidence. LEARNING OBJECTIVES Distinguish between class and individual characteristics. ...

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


Comparison Samples

Known samples Standard or reference sample Control or blank sample Elimination sample


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


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


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.


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.


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.


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


Major Fingerprint Patterns


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


Methods Of Developing Latent Prints Traditional powders Fluorescent Powders Chemicals Cyanoacrylate of superglue fuming Visualization under:

Laser Alternative light Ultraviolet illumination


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.


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)

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Portable Superglue Fuming Chamber Easy to use Produces remarkable results Low cost


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


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)

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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.


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


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.


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?


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.


Questioned Documents

Handwriting and handprinting examinations

There are three types of forgery: Traced forgery Simulated forgery Freehand forgery


Questioned Documents continued

Photocopier examination Paper examination Age of documents Burned or charred paper Altered or obliterated writing Writing instruments mechanical-impression instruments Typewriting


Physical Evidence. LEARNING OBJECTIVES Distinguish between class and individual characteristics. ...

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