CTE Forensics/Law & Public Safety 1-2 Unit 2 Physical Evidence.

CTEForensics/Law &

Public Safety1-2

Unit 2 Physical Evidence

© 2013 by Pearson Higher Education, IncUpper Saddle River, New Jersey 07458 • All Rights Reserved

Learning Standards and Objectives

CTE: 4.0 = Compare/Contrast Safety Precautions & Procedures in Law, Public Safety, & Security (4.1); 6.0 = Analyze Investigative Procedures (6.1 - 6.7); Science: Strand 1 - Concept 1 PO 1 - 4; Concept 2 PO 1 - 5; Concept 4 PO 1 - 4

Students will be able To:

evaluate various evidence collection techniques and crime scene preservation. Evaluate the process of crime scene investigation: searching, photography, sketching, measuring, identification, labeling, collecting, and packaging of evidence.

MEASUREMENTS:

Quizzes, class discussions, comprehension

assessments and Performance Assessments (Labs).

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Learning Objectives

STUDENTS WILL BE ABLE TO AND COMPREHEND:

•Define Physical Evidence

•Discuss the Responsibilities of the first police officer who responds to a crime scene (responding officer).

•Explain the steps taken in recording a crime scene

•Describe proper procedures for conducting a systematic search of a crime scene for physical evidence

•Describe proper collection and packaging of common types of physical evidence.

•Define “chain of custody”

•Discuss the roles and duties of Forensic Scientists at a crime scene.

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KEY TERMS – Be prepared to have a Quiz

PHYSICAL EVIDENCE

CHAIN OF CUSTODY

STANDARDS/REFERENCE SAMPLE

SUSTRATE CONTROL

ROUGH SKETCH

FINISHED “FINAL SKETCH”

ALGO MORTIS

LIVOR MORTIS

RIGOR MORTIS

AGGLUTINATION

AUTOPSY

BUCCAL SWAB

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Crime Scene Physical Evidence

• Write the following above the tri-circle graph

Forensic science begins at the crime scene.

Physical evidence - objects that can establish that a crime has or has not been committed or can provide a link between a crime and its victim or a crime and its perpetrator.

If the investigator cannot recognize physical evidence or cannot properly preserve it for laboratory examination, no amount of sophisticated laboratory instrumentation or technical expertise can salvage the situation.

http://youtu.be/oIr-svyUDKo

http://youtu.be/TqKq6nYK9mA

http://youtu.be/0S9oks0-rqU


Types of Physical Evidence

Blood, semen, and saliva

Documents

Drugs

Explosives

Fibers

Fingerprints

Firearms and ammunition

Glass

Hair

Impressions

Organs and physiological fluids

Paint

Petroleum products

Plastic bags

Plastic, rubber, and other polymers

Powder residues

Soil and minerals

Tool marks

Vehicle lights

Wood and other vegetative matter


Crime Scene Physical Evidence

• Almost anything can be physical evidence.

http://youtu.be/EQUE8IeVmpA

• The purpose of recognizing physical evidence is so that it can be collected and analyzed.

• It is difficult to ascertain the weight a given piece of evidence will have in a case, as ultimately the weight will be decided by a jury

http://youtu.be/jcypaqcKesU

Write in the Tri-Circle Graph


Purpose of Examining Physical Evidence

• Identification to determine the physical or chemical identity of a substance.

http://youtu.be/TKeHnqkvrEw

• Comparison analysis subjects a suspect specimen and a standard/reference specimen to the same tests and examinations for the ultimate purpose of determining whether or not they have a common origin

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Identification

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The object of an identification is to determine the physical or chemical identity with as near absolute certainty as existing analytical techniques will permit.

• The process of identification first requires the adoption of testing procedures that give characteristic results for specific standard materials.

• Once these test results have been established, they may be permanently recorded and used repeatedly to prove the identity of suspect materials.

• Second, identification requires that the number and type of tests needed to identify a substance be sufficient to exclude all other substances.


Common Types of Identification

1. Chemical composition of illicit drugs

2. Gasoline residues from debris of a fire

3. Explosive residues; for example, dynamite, TNT

4. Blood, semen, hair, or wood

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Comparison and Procedure

A comparative analysis has the important role of determining whether or not a suspect specimen and a standard/reference specimen have a common origin.

Both the standard/reference and the suspect specimen are subject to the same tests.

1. Combinations of select properties are chosen from the suspect and the standard/reference specimen for comparison.

2. Once the examination has been completed, the forensic scientist must be prepared to render a conclusion with respect to the origins.

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Role of Probability

• Simply defined, probability is the frequency of occurrence of an event.

• In flipping a coin, probability is easy to establish.

• With many analytical processes exact probability is impossible to define. (or is it…)

http://youtu.be/uzkc-qNVoOk

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Classifying Characteristics

Evidence that can be associated to a common source with an extremely high degree of probability is said to possess individual characteristics.

• In all cases, it is not possible to state with mathematical exactness the probability that the specimens are of common origin.

• It can only be concluded that this probability is so high as to defy mathematical calculations or human comprehension.

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Individual Characteristics

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Examples: • The matching ridge characteristics of two fingerprints• The comparison of random striation markings on bullets

or tool marks• The comparison of irregular and random wear patterns

in tire or footwear impressions• The comparison of handwriting characteristics• The fitting together of the irregular edges of broken

objects in the manner of a jigsaw puzzle • Matching sequentially made plastic bags by striation

marks running across the bags


Class Characteristics

• Surprising to the inexperienced is the frequent inability of the laboratory to relate physical evidence to a common origin with a high degree of certainty.

• Evidence is said to possess class characteristics when it can be associated only with a group and never with a single source.

• Nevertheless, the high DIVERSITY of class evidence in our environment makes their comparison very significant in the context of a criminal investigation.

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Procedures for Collection

Often, many items of evidence are clearly visible but others may be detected only through examination at the crime laboratory.

For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fingernail scrapings, in addition to more discernible items.


Class Evidence

Evidence is said to possess class characteristics when it can be associated only with a group and never with a single source.

Nevertheless, the high DIVERSITY of class evidence in our environment makes their comparison very significant in the context of a criminal investigation.

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Value of Class Evidence

• One of the current weaknesses of forensic science is the inability of the examiner to assign exact or even approximate probability values to the comparison of most class physical evidence.

• For example, what is the probability that a nylon fiber originated from a particular sweater, or that a paint chip came from a suspect car in a hit and run?

• There are very few statistical data available from which to derive this information, and in a mass-produced world, gathering this kind of data is increasingly elusive.

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Value of Class Evidence Cont.

• One of the primary endeavors of forensic scientists must be to create and update statistical databases for evaluating the significance of class physical evidence.

• Most items of physical evidence retrieved at crime scenes cannot be linked definitively to a single person or object.

• The value of class physical evidence lies in its ability to provide corroboration of events with data that are, as nearly as possible, free of human error and bias.

• Because of its DIVERSITY, the chances are low of encountering two indistinguishable items of physical evidence at a crime scene that actually originated from different sources.

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Value of Class Evidence Cont.

• When one is dealing with more than one type of class evidence, their collective presence may lead to an extremely high certainty that they originated from the same source.

• Finally, the contribution of physical evidence is ultimately determined in the courtroom.

• Just as important, a person may be exonerated or excluded from suspicion if physical evidence collected at a crime scene is found to be different from standard/reference samples collected from that subject.

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Pick a Penny LAB

Object:

1. Describe and understand the importance of observation skills in identification.

2. Improve your attention to detail

3. Explain the importance of ethics in Law & Public Safety.

LAB:

Continue to read the instruction and complete activity

Questions must be answered in detail when finished.

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Crossing Over

Crossing over the line from class to individual does not end the discussions.

• How many striations are necessary to individualize a mark to a single tool and no other?

• How many color layers individualize a paint chip to a single car?

• How many ridge characteristics individualize a fingerprint?

• How many handwriting characteristics tie a person to a signature?

These are all questions that defy simple answers and are the basis of arguments.

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Nature vs. Evidential Limits

There are practical limits to the properties and characteristics the forensic scientist can select for comparison.

• Modern analytical techniques have become so sophisticated and sensitive that natural variations in objects become almost infinite.

• Carrying natural variations to the extreme, no two things in this world are alike in every detail.

• Evidential variations are not the same as natural variations.

• Distinguishing variations of evidential use from natural variations is not always an easy task.

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Forensic Databases

The Integrated Automated Fingerprint Identification System (IAFIS) is a national fingerprint and criminal history system maintained by the FBI and launched in 1999. It contains fingerprints for nearly 68 million subjects.

The Combined DNA Index System (CODIS) enables federal, state, and local crime laboratories to electronically exchange and compare DNA profiles. Launched in 1998, it contains 350,000 profiles in its forensic index from unsolved crimes.

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Forensic Databases Cont.

The National Integrated Ballistics Information Network (NIBIN) allows firearm analysts to acquire, digitize, and compare markings made by a firearm on bullets and cartridge casings. Nearly 1.6 million items have been entered into the database and 34,000 hits have been recorded.

The International Forensic Automotive Paint Data Query (PDQ) database contains chemical and color information pertaining to original automotive paints. Contains information about 13,000 vehicles

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Forensic Databases Cont.

SICAR (Shoeprint Image Capture and Retrieval) is a shoeprint database. This product has a comprehensive shoe sole database (SoleMate®) which contains more than 22,000 footwear patterns.

A second database, TreadMate®, also has been created to house tire tread patterns. Currently, it contains 6,000 records

Comprehension Assessment:

Can you find a free online data bank that starts with a G…?26

Add to the bottom of the Database Slide


Forensic Palynology

Forensic palynology involves the collection and examination of pollen and spores connected with crime scenes, illegal activities, or terrorism. The microscope is the principal tool used in the field of forensic palynology.

The information gained from the analysis of pollen and spore evidence has many possible uses. It can link a suspect or object to the crime scene or the victim, prove or disprove a suspect ’s alibi, include or exclude suspects, track the previous whereabouts of some item or suspect, or indicate the geographical origin of some item

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CTE Forensics/Law & Public Safety 1-2 Unit 2 Physical Evidence.

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Transcript of CTE Forensics/Law & Public Safety 1-2 Unit 2 Physical Evidence.