cte forensics/law & public safety 1-2 unit 4 trace evidence i: hairs and fibers

CTE Forensics/Law & Public Safety

1-2

Unit 4

Trace Evidence I:Hairs and Fibers

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

Learning Standards and Objectives

CTE: 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; Strand 2 - Concept 1 PO 1 - 4; Strand 3 - Concept 2 PO 2; Strand 4 - Concept 1 PO 1 - 5, Concept 2 PO 1 – 4; Strand 5 - Concept 1 PO 1,2, & 4; Strand 6 - Concept 3 PO 9.

Students will be able To:

evaluate the use of the microscope for trace evidence and hair/fibers. To distinguish the history, characteristics, physiology, patterns, types, development & preservation; Continue to evaluate trace evidence (glass, paint, soil) using a comparison microscope; practicum exercise.

Measurements: : Quizzes, class discussions, comprehension assessments, performance assessments (labs).

MEASUREMENTS: Quizzes, class discussions, comprehension assessments, performance assessments (labs).

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Learning Objectives

Identify and Describe the hair cuticle, cortex and medulla

Describe the three phases of hair growth

Identify and Explain the distinction between animal and human hair

List hair features that are useful for the microscopic comparison of human hairs

Explain the proper method of collection of hair evidence

Describe the role of DNA typing in hair comparisons

Classify fibers

Describe the structure of a polymer

List the properties of fibers that are most useful for forensic comparisons

Describe the proper method of collection of fiber evidence

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Key Terms – Be prepared for a Quiz

Anagen phase Monomer

Catagen phase Natural Fibers

Cortex Nuclear DNA

Cuticle Polymer

Follicular tab Telogen phase

Macromolecule

Manufactured fibers

Medulla

Mitochondrial DNA

Molecule

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Introduction

• Hair is encountered as physical evidence in a wide variety of crimes.

• Although it is not yet possible to individualize a human hair to any single head or body through its morphology, it still has value as physical evidence.

• When properly collected and submitted to the laboratory, accompanied by an adequate number of standard/reference samples, hair can provide strong corroborative evidence for placing an individual at a crime scene.


Morphology of Hair

• Hair is an appendage of the skin that grows out of an organ known as the hair follicle.

• The length of a hair extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end.

• It is the shaft, which is composed of three layers—the cuticle, cortex, and medulla—that is subjected to the most intense examination by the forensic scientist.


Cuticle and Cortex

• The cuticle is the scale structure covering the exterior of the hair.

– The scales always point towards > tip of the hair.

– The scale pattern is useful in species identification.

• The cortex is the main body of the hair shaft.– Its major forensic importance is the fact that it is embedded

with the pigment granules that impart hair with color.

– The color, shape, and distribution of these granules provide the criminalist with important points of comparison among the hairs of different individuals.

James O'Sullivan

Insert fig 13-1


Examination of Hair

Comprehension Assessment:Look familiar? Label the sections of the skin…


Medulla

The medulla is a cellular column running through the center of the hair.

• The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft.

• For humans, the medulla generally occupies less than one-third the diameter of the shaft, while for animals it is generally one-half or greater.

• The medulla may be continuous, interrupted, fragmented, or absent.

• The presence of the medulla vary from individual to individual and even among hairs of a given individual.

• Medullae also have different shapes, depending the species.


Root

• The hair root is determined by hair’s current growth phase:

- Anagen phase- Catogen phase- Telogen phase

• When pulled from the head, some white or clear looking tissue surrounding the hair’s shaft near the root may be found. This is called a follicular tag.

• By using DNA analysis on the follicular tag, the hair may be individualized.


Comparing Strands• The comparison microscope is an indispensable tool for

comparing the morphological characteristics of hair. • Scale structure, medullary index, and medullary shape are

particularly important in animal hair identification.• When comparing strands of human hair, the criminalist is

particularly interested in matching the color, length, and diameter. • Other important features for comparing human hair are:

–The presence or absence of a medulla.–The distribution, shape, and color intensity of the pigment granules present in the cortex.

• The most common request is to determine whether or not hair recovered at the crime scene compares to hair removed from the suspect.

• However, microscopic hair examinations tend to be subjective and highly dependent on the skills and integrity of the analyst. For this reason a reported hair comparison must contain DNA information.


GET A NUMBER 2 YELLOW PENCIL WITH ERASERPULL 1 STRAND OF YOUR HAIR OUT (BIG BABY!)

• THE STRUCTURE OF A HAIR CAN BE COMPARED TO A NUMBER 2 PENCIL

• LAY YOUR PENCIL DOWN NEXT TO THE STRAND OF HAIR

• NOW THINK OF THE PENCIL AS YOUR HAIR AND ANSWER THE QUESTIONS ON THE WORKSHEET WITH THE PENCIL.

COMPREHENSION ASSESSMENT: NEXT PAGE

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Questions

• Can the body area from which a hair originated be determined?

• Can the racial origin of hair be determined?

• Can the age and sex of an individual be determined from a hair sample?

• Is it possible to determine if a hair was forcibly removed from the body?

• Are efforts being made to individualize human hair?


ANSWERS TO YOUR ASSESSMENT

1. ORIGINATION CAN ONLY BE ASSUMED/SOMATIC ORIGIN (UNLESS MITOCHONDRIAL DNA IS FOUND) IT WILL BE CHALLENGED IN COURT BY LAWYERS.

2. RACIAL ORGIN CAN ONLY BE ASSUMED (UNLESS MITOCHONDRIAL DNA IS FOUND) IT WILL BE CHALLENGED IN COURT BY LAWYERS.

3. AGE AND SEX OF HAIR SAMPLES CAN NOT BE DETERMINED ONLY ASSUMED (UNLESS MITOCHONDRIAL DNA IS FOUND) IT ALL WILL BE CHALLENGED IN COURT BY LAWYERS.

4. YES, IF HAIR IS FORCIBLY REMOVED FROM THE BODY, THE DYNAMICS OF THE HAIR STRAND WILL SHOW “TEARING, CUTTING, PULLED OR RIPPED OUT ROOTS, ETC. AGAIN, IT WILL ALWAYS BE CHALLENGED IN COURT.

5. YES! FORENSIC SCIENCE IS ALWAYS LOOKING FOR NEW TECHNOLOGY AND METHODS TO IDENTIFY TRACE EVIDENCE.

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Major Elements of Hair

1. Keratin is a protein that makes up most of the hair shaft. 2. Melanin is a pigment that gives hair its color.


3. Redheads have pheomelanin instead of melanin.

Baby Hair

Typical Adult HairSplit Ends(Cuticle Damage)

Human Hair with split ends

HairTreatments

Dark, Blonde White

African

Asian

Caucasian


1. The cortex is the main body of a hair (compared to the wooden portion of a pencil)


2. The medulla is the central cell of the cortex (compared to the lead of a pencil). The medulla is not present in every hair.


3. The cuticle is a layer of scales covering the hair shaft (compared to a layer of yellow paint on a pencil).


4. The root is also known as the “proximal end” (compared to the eraser on a pencil).


5. The tip is also known as the “distal end” (compared to the sharpened tip of a pencil).


1. Pigment colors (light, medium, dark, reddish brown, brown, black, etc.)2. Pigment Sizes (fine, moderate, large) 3. Pigment density (light, moderate, heavy)

Characteristic Comparisons


Hair and DNA

• Recent major breakthroughs in DNA profiling have extended this technology to the individualization of human hair.

• The probability of detecting DNA in hair roots is more likely for hair being examined in its anagen or early growth phase as opposed to its catagen (middle) or telogen (final) phases.

• Often, when hair is forcibly removed, a follicular tag—a white/clear looking piece of tissue surrounding the hair ’s shaft near the root—may be present.

• This has proven to be a rich source of nuclear DNA associated with hair.


Hair and Mitochondrial DNA

• Mitochondrial DNA can be extracted from the hair shaft.

• Mitochondrial DNA is found in cellular material located outside of the nucleus and it is transmitted only from the mother to child.

• Mitochondrial DNA has a high frequency of occurrence in a population and thus cannot be used to individualize a hair, but it does provide valuable corroboration of a morphological hair comparison.

• As a rule, all positive microscopical hair comparisons must be confirmed by DNA analysis.


HAIR TYPING

SOMATIC ORIGIN – hairs from different parts of the body have different characteristics

1. Head hairs are typically straighter than other hair on the body. They are generally softer, and are the most likely to have color treatments.

2. Pubic hairs are typically shorter in diameter, with wide variations. Buckling is a special characteristic found in pubic hairs.

Draw what you believe buckling means on your paper

Be appropriate Gomers!

3. Limb hairs tend to be short and soft. Their tips are usually frayed or abraded.

4. Facial hairs are very short with irregular or triangular cross sections. Their medullae may be very broad, even double.

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Collection and Preservation

• As a general rule, forensic hair comparisons involve either head hair or pubic hair.

• The collection of 20-50 full-length hairs from all areas of the scalp will normally ensure a representative sampling of head hair. Most departments do not collect that many hairs.

• A minimum collection 12-24 full-length pubic hairs should cover the range of characteristics present in pubic hair.

• Hair samples are also collected from the victim of suspicious deaths during an autopsy.


Vocabulary Quiz AH GEEZ

TOLD YOU SO!

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Types of Fibers

• Natural fibers are derived in whole from animal or plant sources. For example:

– Wool– Mohair– Cashmere– Furs– Cotton

• Man-made fibers are manufactured.– Regenerated fibers are manufactured from natural raw

materials and include rayon, acetate, and triacetate.– Synthetic fibers are produced solely from synthetic chemicals

and include nylons, polyesters, and acrylics.

http://youtu.be/yeAwJwuUQH8


Fiber Evidence

• The quality of the fiber evidence depends on the ability of the criminalist to identify the origin of the fiber or at least be able to narrow the possibilities to a limited number of sources. The forensic value of fiber evidence is its diversity in our environment.

• Obviously, if the examiner is presented with fabrics that can be exactly fitted together at their torn edges, it is a virtual certainty that the fabrics were of common origin.

• Microscopic comparisons between questioned and standard/reference fibers are initially undertaken for color and diameter characteristics, using a comparison microscope.

• Other morphological features that could be important in comparing fibers are:

1. Lengthwise striations on the surface of the fiber.2. The presence of delustering particles that reduce shine.3. The cross-sectional shape of the fiber.


Methods for Fiber Comparison

• The microspectrophotometer is a combination of a traditional light microscope and a spectrophotometer. It allows a forensic analyst to view an object under a microscope while simultaneously obtaining its visible of infrared absorption pattern.

• The visible light microspectrophotometer is a convenient way for analysts to compare the colors of fibers through spectral patterns.

• Infrared spectrophotometry is a rapid and reliable method for identifying the generic class of fibers.

• The molecules that compose a manufactured fiber selectively absorb infrared light to form a characteristic pattern.


Fiber Collection and Preservation

• FORENSIC investigator’s search/collect strands of fibers to identify and preserve potential crime scene fiber evidence.

• Clothing should be packaged carefully in separate brown paper or brown paper bags. Depends on team policy.

• If it is necessary to remove a fiber from an object, the investigator must use clean forceps (tweezers), place it on a small sheet of paper, or plastic sheet. Carefully cover the hair with another piece of paper or plastic and label. Label and Package in an evidence envelope to size.


Vocabulary Quiz

Crime scene investigators (yah, yah, yah, students count)

DON’T WHINE!AFTER YOU ARE DONE WITH YOUR VOCAB.

1. READ & ANALYZE THE HAIR AND FIBER ARTICLE. DON’T HIGHLIGHT THE ENTIRE THING. WRITE 5 “GOOD” TEXT DEPENDENT QUESTIONS.

2. MAKE SURE YOU ARE ABLE TO IDENTIFY HAIR TYPING AND OTHER CHARACTERISTICS OF HAIR AND FIBER TO BE SUCCESSFUL ON THE TEST.

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Forensic Science Hair LabFollow the directions in your teams

(Lead Detectives delegate orders and are responsible)

“Trouble goes to the top and runs down from there”

1. Each individual in the team must make 10 fold packages. (we will be using the extras later in labs)

2. Collect 2 hairs from each of your team members.

3. All Team members place 1 of the 2 hairs in a container. Label Control “Case # is 2014 1234567 (also referred to as DR #)

4. Take the second hair and place individual hairs in separate fold packages. Label Evidence.

5. Should have (if) 4 team members, 4 control packages and 4 crime scene packages.

6. Now, swap your 8 with another team. (repeat with every team)

7. Identify which crime scene hair matches which control sample.

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Forensic Science Fiber Lab

Discover fiber typing using the microscopes.

Document the differences amongst fiber types.

Compare the fibers to your unit packet fiber picture examples.

Note and document the differences between NATURAL AND SYNTHETIC FIBERS

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cte forensics/law & public safety 1-2 unit 4 trace evidence i: hairs and fibers

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