UNIT 2: THE CRIME SCENE Collection, Protection and Analysis of Physical Evidence from the Crime Scene

UNIT 2: THE CRIME SCENE

Collection, Protection and Analysis of Physical Evidence from

the Crime Scene

UNIT 2: DAY 1

Do Now: What is the most important

thing for the first Police Officer to do

when they enter a crime scene?

LEARNING OBJECTIVES

Today Students will:

Define Physical Evidence

Understand the responsibilities of the First

Police Officer to arrive at a crime scene

Demonstrate the steps to be taken to

thoroughly record the crime scene

4

PHYSICAL EVIDENCE

As automobiles run on gasoline, crime laboratories “run” on

physical evidence.

Physical evidence encompasses any and all objects that can

establish that a crime has been committed or can provide a link

between a crime and its victim or a crime and its perpetrator.

If physical evidence is to be used effectively for aiding the

investigator, its presence first must be recognized at the crime

scene.

5

THE BEGINNING: THE CRIME SCENE

Forensic science begins at the crime scene.The investigator must complete 2 essential functions:

• recognize physical evidence• properly preserve it for laboratory

examination The techniques of crime-scene investigation are not difficult to master, it is expected that the average police officer be able to perform them properly.

6

THE FIRST STEP: SECURE THE SCENE

The first officer to arrive at the scene is responsible for securing the crime scene.

• However, first priority is given to obtaining medical assistance and/or to arresting the perpetrator.

As soon as possible, exclude all unauthorized personnel from the scene. Once the scene is secured, the preliminary exam must begin.

• Recording the crime scene becomes a critical piece to the investigation process.

7

CRIME SCENE RECORDING METHODS

Three methods for crime-scene recording• Photography • Sketching • Note taking

Ideally all three should be employed at each crime scene

• Often personnel and monetary limitations may prohibit the utilization of photography at every crime site.

8

PHOTOGRAPHY OF A CRIME SCENE

The crime scene must be in an unaltered condition.

Objects must not be moved until they have been photographed from all necessary angles, (unless there are injured parties involved).

As items of physical evidence are discovered, they are photographed to show their position and location relative to the entire scene.

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PHOTOGRAPHY

After the overviews are taken, close-ups should be taken to record the details of the object itself. •When the size of an item is of significance, a ruler or other measuring scale may be inserted near the object and included in the photograph as a point of reference.

PRACTICE PHOTOGRAPHING A SCENE

(15 min) In teams of 3-4• Experiment with how your camera works, please be

careful• Use your camera to photograph your table, like a

crime scene, according to the notes just given• Take at least five pictures which you think are

relevant.

(20 min)Share pictures and discuss their

effectiveness in documenting the scene.

UNIT 2: DAY 2

Do Now: What are two important things

to be sure to do when photographing a

crime scene?

LEARNING OBJECTIVE

Today students will:

Demonstrate the steps to be taken to thoroughly

record the crime scene

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SKETCHESRough Sketch— A draft representation of all essential information and measurements at a crime scene.

• This sketch is drawn at the crime scene.• It shows all recovered items of physical evidence,

as well as other important features of the crime scene.

Finished Sketch— A precise rendering of the crime scene, usually drawn to scale.

• This type is not normally completed at the crime scene.• The finished sketch is drawn with care and

concern for aesthetic appearance.

SKETCHING PRACTICE

(8 min) Each person should do a rough sketch of

everything on the lab table.

(3 min) Compare your sketches to those on your

table.• How are they different?• Did anyone see anything you did not? Why?• How can you be more accurate in the future?

WHY SKETCH?

Think (2 min), Pair (4 min) , Share(5min)

What is the value of sketching?

How does it compare, in importance, to

photography?

What additional value is added to the evidence by

sketching?

What are the essential characteristics of a sketch?

How are rough sketches and finished sketches

different?

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NOTESNote taking must be a constant activity throughout the processing of the crime scene. They must include a detailed written description of the scene with the location of all items of physical evidence recovered. They must identify:

• The time each piece of physical evidence was discovered• Who discovered it• How and by whom it was packaged and marked• What happened to the item after it was collected

This written record may be the only source of information for refreshing one’s memory .

PRACTICE NOTE TAKING

(4 min) Complete a set of notes for this “Crime

Scene”

Be sure to include all relevant info.

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RECORDING THE CRIME SCENE

Investigators have only a limited amount of time to work a crime site in its untouched state. The opportunity to permanently record the scene in its original state must not be lost. Such records will not only prove useful during the subsequent investigation but are also required for presentation at a trial

• in order to document the condition of the crime site and to delineate the location of physical evidence.

Every step of the investigation should be documented thoroughly with an appropriate method.

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THE PRELIMINARY EXAM

A lead investigator will start the process of evaluating the area.

• First, the boundaries of the scene must be determined.

• Followed by the establishment of the perpetrator’s path of entry and exit.

• The investigator then proceeds with an initial walk-through of the scene to gain an overview of the situation and develop a strategy for the systematic examination and documentation of the entire crime scene.

This is done before processing the crime scene for physical evidence.

UNIT 2: DAY 3

Do Now: What are the steps that must

be taken to thoroughly record the

crime scene?

LEARNING OBJECTIVES


Describe proper procedures for conducting a

systematic search for physical evidence

Describe proper procedures for packaging

common types of physical evidence

Define and understand “chain of custody”

24

THE SEARCH OF THE CRIME SCENE

The search for physical evidence must be thorough and systematic. The search pattern selected will normally depend on:

• the size and locale of the scene • the number of collectors participating in the search.

For a factual, unbiased reconstruction of the crime, the investigator—relying upon training and experience—must not overlook any pertinent evidence. Physical evidence can be anything from massive objects to microscopic traces.

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THE SEARCH

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.

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BEYOND THE CRIME SCENE

The following are to be collected and sent to the forensic laboratory:1. Victim’s clothing2. Fingernail scrapings3. Head and pubic hairs4. Blood (for DNA typing purposes)5. Vaginal, anal, and oral swabs (in sex related

crimes)6. Recovered bullets from the body7. Hand swabs from shooting victims (for gunshot

residue analysis)

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BEYOND THE CRIME SCENE: AUTOPSY

The search for physical evidence must extend beyond the crime scene to the autopsy room of a deceased victim.

• The medical examiner or coroner will carefully examine the victim to establish a cause and manner of death. (Why and How)

• Tissues and organs will be retained for pathological and toxicological examination.

Arrangements must be made, between the examiner and investigator to ensure that a variety of items that may be obtainable from the body are secured.

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PACKAGING EVIDENCE

Each different item or similar items collected at

different locations must be placed in separate containers. • Packaging evidence separately prevents damage

through contact and prevents cross-contamination.

The well-prepared evidence collector will arrive at a

crime scene with a large assortment of packaging

materials and tools ready to encounter any type of

situation.

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PACKAGING TOOLSForceps and similar tools may have to be used to pick up small items. Unbreakable plastic pill bottles, with pressure lids, are excellent containers for hairs, glass, fibers, and various other kinds of small or trace evidence. Alternatively, manila envelopes, screw-cap glass vials, or cardboard pillboxes are adequate containers for most trace evidence encountered at crime sites.

• Ordinary mailing envelopes should not be used as evidence containers because powders and fine particles will leak out of their corners.

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PACKAGING TOOLS

Small amounts of trace evidence can also be conveniently packaged in a carefully folded paper, using what is known as a “druggist fold.”

This type of packaging is called a Paper Bindle

PRACTICE MAKING A PAPER BINDLE

Follow the directions on the hand out, carefully.When you have completed your first attempt, continue to practice until you can do it without the directions.When you are ready, work with a partner to each make a paper bindle and insert the provided trace evidence in it. Pass your bindle to your partner who will test it to see if any evidence is being lost.When your bindle is approved by your partner, let me know by posting a sticky note on your station.

UNIT 2: DAY 10

Do Now•What kinds of packaging tools should an investigator bring to the crime scene?•What one thing was frequently missing from our crime scene presentations?

LEARNING OBJECTIVE

Today Students will:Justify their decision about what type of search pattern should be used at particular types of crime scenesIdentify indicators of where to find important evidence to collect based on the circumstances

Recognize techniques for handling evidence

Explain the importance of Chain of Custody

Understand when to collect “Reference Samples”

THE SEARCH FOR EVIDENCE

The investigator in charge assigns responsibility of searching a crime scene.Whenever possible, 1 person should supervise evidence collection

• A forensic scientist is usually NOT involved, their work begins in the lab

• Some police agencies have trained field evidence collection technicians who search for evidence

The type of search pattern used depends on the location and size of the area, as well as the actions of the suspect(s) and victim(s) at the scene.Proper control of the search is important, to minimize confusion and ensure that no evidence is left behind

SEARCH PATTERNS

When attempting to locate evidence, detectives must be methodical.

One way to be certain they’ve combed every inch of a crime scene

is to conduct structured, patterned searches, such as spiral or grid

searches.

Five Different Search Patterns1.Strip or Line Search2.Grid Search3.Spiral Search4.Wheel/Ray Search5.Quadrant or Zone Search

1. STRIP OR LINE SEARCH

One or two investigators start walking in a straight line,

perpendicular to the boundary edge

They walk straight across to the opposite side boundary

edge

They then move further over on the boundary and walk

back to the original side

They then repeat the walk back and forth until they cover

the entire search area

STRIP OR LINE SEARCH

• The space to be

searched is divided into a series of lanes

• One or more searchers proceed up and down the lane, continuing until the area has been completely searched.

2.GRID SEARCH

Consists of two strip

searches, the second

perpendicular to the first

Allows the area to be

viewed

from two angles therefore is

very thorough.

Must have well established

boundaries

Good for large search

areas

3. SPIRAL SEARCH

• Typically used outdoors• Normally launched by a

single person who begins at the outermost corner and walks in a decreasing spiral toward a central point.

• Inward is helpful because the investigator moves from an are light with evidence to an area with more

• Can also be conducted from the center out

• A perfect spiral is difficult to do

4. WHEEL/RAY SEARCH

• A search pattern in which the area is divided into pie-shaped sections, usually six in number.

• Several people move from the boundary straight toward the center

• This is not the preferred method because the area between the rays is not well searched

5. QUADRANT OR ZONE SEARCH

• The area is divided into quadrants, each of which is then examined with one of the other patterns.

• Team members are assigned to search specific quadrants

• Search must include all probable points of entry and exit

• Well suited for large search areas

LOCATING PHYSICAL EVIDENCE

The investigators skill in recognizing evidence is

very important in effective crime scene processing

Experience plays a major role in helping

investigators develop a successful strategy for

recovering relevant physical evidence

The circumstances of the crime help detectives

know what to look for

PHYSICAL EVIDENCE IN DIFFERENT CIRCUMSTANCES

Homicides: search centers on the weapon and cross-transfer evidence between the victim and the perpetrator, (hairs, blood, and fibers)Burglaries: search focuses on points of entry and tool marksA careful search for latent fingerprints is required at most crime scenes

PHYSICAL EVIDENCE IN DIFFERENT CIRCUMSTANCES

Vehicle Searches: Must be carefully planned and systematically executed

• The amount of detail paid in the search depends on the nature of the case• Hit and Run: careful search of outside and

undercarriage is important. (evidence from cross0transfer between car and victim (blood, tissue, hair, fibers, fabric impressions, paint traces or glass fragments)

• Homicide, Burglary, Kidnapping: all areas both inside and out are searched thoroughly

COLLECTING PHYSICAL EVIDENCE

Some evidence is obvious, other evidence can only be detected in the lab• Trace blood evidence, hairs and fibers may only be revealed through vacuum

sweeping or on clothes only after close scrutiny in the lab

It is essential to collect all possible carriers of trace evidence• Often all clothing worn by crime participants is collected• Each clothing item should be wrapped separately

Critical areas should be vacuumed and sweepings should be sent to the

lab• Sweepings from different areas should be packaged separately

Fingernail scrapings should be collected from anyone who was in contact

with others• Scrape undersurface with a dull object, like toothpick (do not cut skin)- to lab

HANDLING EVIDENCEHandled in a way that leaves evidence unchanged between the scene and the lab

• Avoid contamination, breakage, evaporation, scratching or bending which can occur as a result of poor packaging or careless handling

Use latex gloves and/or forceps when touching evidence• Be sure to sanitize tools between each piece of evidence

Investigators should not remove blood, hairs, fibers, soil particles, or anything else from clothes, weapons or other articles

• Send the entire object to the labUse common sense when dealing with evidence on a large structure (door, wall, or floor) remove it with appropriate tool

HANDLING BLOOD EVIDENCE

Bloodstains, options• Scrape stain off the surface• Transfer the stain to a moistened swab• Cut out the area of the object bearing the stain

Which to do must be decided by the

investigators on scene

PACKAGING

Although pill bottles, vials, pillboxes, or manila envelopes are good universal containers for most trace evidence, one frequent find at crime scenes warrants special attention.

• bloodstained materials (collect with disposable tools)• if stored in airtight containers, the accumulation of

moisture may encourage the growth of mold, which can destroy the evidential value of blood.

• In these instances, wrapping paper, manila envelopes, or paper bags are recommended packaging materials

DNA EVIDENCE

Can be found in really tiny samples on evidence which has come

into contact with sweat, saliva or skin cells

Search should include all objects which the suspect or victim may

have come into bodily contact with

Likely sources• Stamps and envelopes• Cup or can• Gum, sweatband of a hat or bed sheet

Collect wearing a face mask , as well as disposable gloves and

forceps, (sometimes coveralls and shoe covers are also worn)

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CHAIN OF CUSTODYChain of Custody—A list of all persons who came into possession of an item of evidence.Continuity of possession, or the chain of custody, must be established whenever evidence is presented in court as an exhibit. Adherence to standard procedures in recording the location of evidence, marking it for identification, and properly completing evidence submission forms for laboratory analysis is critical to chain of custody.

• This means that every person who handled or examined the evidence and where it is at all times must be accounted for.

CHAIN OF CUSTODY

Fill out preprinted id forms or attach an evidence tag to every

container

Investigator initials as well as the date must be written on the

evidence seal tape

Every person who possesses the evidence must maintain a

written record of its acquisition and disposition

Often all people involved in the collection and transport of

evidence must testify in court; minimize those in contact with it

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OBTAINING REFERENCE SAMPLES

Standard/Reference Sample—Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence.The examination of evidence, whether it is soil, blood, glass, hair, fibers, and so on, often requires comparison with a known standard/reference sample. Although most investigators have little difficulty recognizing and collecting relevant crime-scene evidence, few seem aware of the necessity and importance of providing the crime lab with a thorough sampling of standard/reference materials.

APPLY YOUR KNOWLEDGE

Each Investigative team will be given a scenario, it is your job to answer all

of the following questions about how you would find and collect the physical

evidence.

Be prepared to report out, write your answers and justifications on a chart

paper:

1. What search method should you use?

2. What type of evidence should you especially be looking for and where

should you look? Why?

3. What special handling and packaging considerations will you have to

address? Why?

4. Should you collect reference samples? If so, from whom or where?

SCENARIOS

1.At a public park, there was a hit and run accident, car vs

pedestrian.

2.Carjacking and abandonment in alley

3.Burglary and assault in Cumberland Farms store

4. Jewelry store robbery, when closed

5.Homicide in car and on pavement in the mall parking

garage

6.Burglary at a private home when owners were on vacation

UNIT 2: DAY 11

Do Now: Why are the procedures for

collecting, packaging and transporting

physical evidence important?

LEARNING OBJECTIVES


Demonstrate ability to select proper search

techniques.

Demonstrate understanding of procedures which will

maintain health and safety standards at the crime scene

Understand the implications of the “Mincey” and

“Tyler” Cases

PREPARE TO REPORT OUT

15 min

Chart your answers

Prepare to explain choices

REPORT CHOICES

20-25 min

Each group has 3-4 minutes

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CRIME SCENE SAFETY

The increasing spread of AIDS and hepatitis B has sensitized the law enforcement community to the potential health hazards that can exist at crime scenes.

• In reality, law enforcement officers have an extremely small chance of contracting AIDS or hepatitis at the crime scene.

The International Association for Identification Safety Committee has proposed guidelines to protect investigators at crime scenes containing potentially infectious materials that should be adhered to at all times.

GUIDELINES TO PROTECT INVESTIGATORS

1.Double glove and shoe covers, sometimes liquid repellant

coveralls

2.Particle mask/respirator, goggles or face shield : when

potentially infectious dust or mist may be encountered

(scraping collection)

3.Be alert to sharps and properly package, use special

fingerprint brush which can be decontaminated

4.Biohazard red bag for glove, clothing, mask, etc disposal

GUIDELINES TO PROTECT INVESTIGATORS

5.Note taking should be done with clean gloves. Pens used to

mark contaminated evidence should be biohazard disposed

6.Remove soiled or torn protective equipment immediately then

decontaminate affected areas

7.Food, drink, makeup application and smoking are prohibited

at crime scene with biological evidence

8.Infectious linen bag (yellow) for non disposable items, washed

by specialized laundry service, through the department –

NEVER TAKE IT HOME

LEGAL CONSIDERATIONS

Pg 46-bottom

In pairs; read the given section and answer the

following questions.

What is unreasonable search and seizure?

What are 4th amendment privileges?

What circumstances allow for a police search,

without a warrant, according to the supreme court?

THE MINCEY AND TYLER CASES

What Important Findings came out of each of these

cases?

In your groups, you will read the synthesis of the

assigned case and explain the implications of the

ruling and explain how it relates to the legal

considerations of evidence collection.• Post your answers on chart paper for report out

UNIT 2: DAY 12

Do Now: What procedures are required

to maintain health and safety standards

at the crime scene?

LEARNING OBJECTIVES


Demonstrate the process of Securing, Isolating and

Recording a crime scene

Explain the Forensic challenges in “ The Enrique

Camarena Case”

Demonstrate understanding of Crime Scene

Processing and Evidence Documentation

QUIZ: THE CRIME SCENE

CASE STUDY: ENRIQUE CAMARENA CASE (50 MIN)

Explain the Forensic challenges in “ The Enrique

Camarena Case”

Work in your groups to address the case study

questions.

Be prepared to report out

UNIT 2: DAY

Do Now: What types of physical

evidence may be collected at the crime

scene?

LEARNING OBJECTIVES (5)


Review common types of evidence

Understand the significance and value of

physical evidence

Compare and contrast identification and

comparison of physical evidence

PHYSICAL EVIDENCEIt is impossible to list all the objects that could conceivably be of importance to a crime.Almost anything can be physical evidence.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 that will be decided by a jury.Although you cannot rely on a list of categories, it is useful to discuss some of the most common types of physical evidence.

TYPES OF PHYSICAL EVIDENCE

1. Blood, semen, and saliva: in a form suggesting a relationship to the crime or the people involved• Set out for serological and biochemical analysis

2. Documents: submitted for authenticity or to determine source3. Drugs: in violation of laws regulating sale, distribution, use or manufacturing4. Explosives: objects containing residue of a discharged explosive or containing and

explosive charge5. Fibers: natural or synthetic; able to establish a relationship between objects and

people6. Fingerprints: latent and visible 7. Firearms and ammunition: all firearms and ammunition, discharged or intact,

suspected to be involved in a criminal case8. Glass: particle or fragment that may have been transferred during a criminal act

( including windows with holes)9. Hair: animal or human which could link a person to a crime10. Impressions: Tire marks, shoe prints, depressions in soil, glove or fabric

impressions, bite-marks on food or skin11. Organs and physiological fluids: submitted for toxicology, looking for drugs or

poisons (blood included)

TYPES OF PHYSICAL EVIDENCE

12.Paint: transferred during a crime, dry or wet13.Petroleum products: gas residue removed from arson scene, grease or oil stains whose presence suggests involvement in a crime

14.Plastic bags: particularly in homicide or drug investigations, links suspect to similar bag in their possession ( reference sample)

15.Plastic, rubber, and other polymers: pieces of these manufactured materials may be linked to objects in possession of suspect

16.Powder residues: items suspected to contain evidence of a discharged firearm

17.Soil and minerals: could link a person or object to a location 18.Tool marks: objects suspected to contain impressions of another object suspected used in a crime

19.Vehicle lights: headlights and tail lights examined to determine if it was on or off at time of impact

20.Wood and other vegetative matter: wood sawdust, shavings, plant material on shoes or tools which may be used to link crime to person or object.

SIGNIFICANCE

For Identification or For Comparison

Identification to determination the physical or chemical

identity of a substance with as near absolute certainty as

existing analytical techniques will permit.

A 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.

IDENTIFICATIONThe 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 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

The crime laboratory is frequently requested to identify the chemical composition of an illicit drug.It may be asked to identify gasoline in residues recovered from the debris of a fire, or it may have to identify the nature of explosive residues—for example, dynamite or TNT.The identification of blood, semen, hair, or wood are also very common and as a matter of routine, include a determination for species origin.

COMPARISONA 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.The forensic comparison is actually a two-step procedure.

• First, combinations of select properties are chosen from the suspect and the standard/reference specimen for comparison.

• Second, once the examination has been completed, the forensic scientist must be prepared to render a conclusion with respect to the origins.

ROLE OF PROBABILITY

To comprehend the evidential value of a comparison, one must appreciate the role that probability has in ascertaining the origins of two or more specimens. 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.

CLASSIFYING CHARACTERISTICS

Individual Characteristics• Evidence that can be associated to a

common source with an extremely high degree of probability is said to possess individual characteristics.

Class Characteristics• Evidence associated only with a group is

said to have class characteristics.

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.

CHARACTERISTICSExamples:

• 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 forensic scientist 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.Here again, probability is a determining factor.Nevertheless, the high diversity of class evidence in our environment makes their comparison very significant in the context of a criminal investigation.

CLASS EVIDENCEOne 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.

CLASS EVIDENCEOne 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.

CLASS EVIDENCEThe chances are low of encountering two indistinguishable items of physical evidence at a crime scene that actually originated from different sources.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.

UNIT 2:

Do Now: What is the difference

between comparison and identification

of physical evidence?

Homework: Prepare for unit test on

Friday!



Explain the differences between types of

evidence and the importance of probability in

their use

Understand the significance of natural

variations

TURN AND TALK (9 MIN)

Provide three examples of evidence collected which would most likely

have individual characteristics• What types of evidence?• How could it be used?• Why do you think this is true?• Is probability important? explain

Provide three examples of evidence collected which would most likely

have class characteristics• What types of evidence?• How could it be used?• Why do you think this is true?• Is probability important? explain

SHARE FINDINGS( 14 MIN)

3 individual characteristic

3 class characteristic

Are there certain types of evidence which usually fall into

one of these categories? Why or why not?

Is one of these types more valuable than the other? Explain

What role does probability play?

How does this compare with common understanding of

evidence value as portrayed on TV?

CROSSING OVERCrossing 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.

NATURAL 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

USING PHYSICAL EVIDENCE

As the number of different objects linking an

individual to a crime scene increases, so does the

likelihood of that individual’s involvement with the

crime.

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.

EXIT TICKET(7 MIN)

1.What are 5 common types of evidence

2.How is physical evidence significant?

3.Is all physical evidence of equal value? Explain as it relates

to probability

4.Compare and contrast identification and comparison of

physical evidence

5.How are class and individual classifications different?

6.What is natural variation and why is it important?

UNIT 2: MARCH 20

Do Now: What is the difference

between natural limits and evidential

limits?

HOMEWORK: Read the case study



List and explain the function of Forensic

Databases

Explain the importance of Forensic

Pathologists, Anthropologists and

Entomologists

DATABASESA database is an organized list of facts and information.

Databases usually contain text and numbers, and frequently hold still

images, sounds and video or film clips.

Government and private forensic databases can help both law

enforcement investigators and the scientists who support their work in the

lab.

They allow the crime lab to link evidence to suspects or crimes

committed using the same tool or pattern.

They make the crime lab a more active component of the investigation by

allowing them to access people and cases in all 50 states and around the

world.

DATA BASESThe Integrated Automated Fingerprint Identification System (IAFIS), a

national fingerprint and criminal history system maintained by the FBI.

The Combined DNA Index System (CODIS) enables federal, state, and local

crime laboratories to electronically exchange and compare DNA profiles.

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.

The International Forensic Automotive Paint Data Query (PDQ) database

contains chemical and color information pertaining to original automotive paints.

SICAR (shoeprint image capture and retrieval) is a shoeprint database.

JIGSAW(20MIN)

Explain the role of Pathologist, Anthropologist, Entomologists in

evidence collection

What kinds of samples do they collect? Be as specific as

possible

How does it inform investigators?• What can they tell us about the victim, perpetrator, crime details?• How accurate are their findings? Probabilities? • Is it usually class or individual?• Are there clear standards used to identify natural variations?

Why are they important?

REPORT OUT

UNIT 2:MARCH 21

Do Now: What type of evidence was

most important in the Wayne Williams

Case?

Homework: Complete chapter 3

review and study for the unit test

which is tomorrow!

LEARNING OBJECTIVES

Today Students Will:

Review the roles of the Forensic Pathologists,

Anthropologists and Entomologists

Evaluate the role of fiber evidence in presenting a case at

trial

Perform a Case Study Analysis

Present findings from a case study of “ the Wayne Williams

Trial”

FORENSIC PATHOLOGY

What is it?

This field involves the investigation of sudden,

unnatural, unexplained, or violent deaths.

What do they do?

The primary role of the medical examiner is to determine

the cause of death.

If a cause cannot be found through observation, an autopsy

is normally performed to establish the cause of death.

FORENSIC PATHOLOGY

How do they do that?

There are several stages of death, these stages are used to establish time of death

Rigor mortis results in the shortening of muscle tissue and the stiffening of body parts

in the position at death (occurs within the first 24 hours and disappears within 36 hours).

Livor mortis results in the settling of blood in areas of the body closest to the ground

(begins immediately on death and continues up to 12 hours). It can also be used to

determine if a body has been moved, (No settling where contacted with surface).

Algor mortis results in the loss of heat by a body (a general rule, beginning about an

hour after death, the body loses heat by 1 to 1-1/2 degrees Fahrenheit per hour until the

body reaches the environmental temperature).

FORENSIC ANTHROPOLOGY

What is it?

Forensic anthropology is concerned primarily with the identification and

examination of human skeletal remains.

What do they do?

Because of their resistance to rapid decomposition, skeletal remains can provide a

multitude of individual characteristics such as sex, approximate age, race, and

skeletal injury.

How do they do it?

The gender of the decedent can be determined by the size and shape of various

skeletal features, especially those in the pelvis and skull or cranium.

The height of the victim when alive can be estimated by measuring the long bones

of the skeleton especially in the lower limbs.

FORENSIC ENTOMOLOGYWhat is it?

The study of insects and their relation to a criminal investigation is known as forensic

entomology.

What do they do?

They estimate the time of death when the circumstances surrounding the crime are unknown.

How do they do it?

This determination can be carried out by studying the stage of development of maggots or

insect sequence of arrival.

After decomposition begins, insects that feed on the dead tissue infest the body and lay eggs,

usually within 24 hours. • The most common and important of these is the blowfly recognized by its green or blue

coloration.

Forensic entomologists can approximate how long a body has been left exposed by

examining the stage of development of the fly larvae.

CASE STUDY ANALYSIS

Analyze the evidence and explain the forensic case

in the Wayne Williams Trial

Work in assigned pairs to address the case study

questions.

Be prepared to report out

REPORT OUT

How was the use of fiber evidence unique, in this case?

What two fibers were of particular importance?

How did investigators gather the evidence provided by the fibers?

What did this evidence tell them, and how did they use it to locate the

perpetrator?

What role did reference samples play in this case?

How were the samples compared? Be specific

How was the concept of probability used in this case?

Why do you think the suspect was only charged with 2 murders?

UNIT 2: MARCH 22

Do Now: Review Unit Concepts

LEARNING OBJECTIVES

Today Students Will:

Demonstrate understanding of unit concepts

on unit assessment

JEOPARDY TIME!(20 MIN)

Compete with your classmates to earn bonus

points on the unit test

CRIME SCENE UNIT TEST

Read the questions carefully and do your best!