Forensics DSL Didn't Wilbur make a lovely chocolate cake last week? Answer: Burma. Didn't Wilbur make a lovely chocolate cake last week?

Forensics Agenda DSL Hair and Fiber analysis notes Worksheet – Due Friday 1/16

Forensics Objectives I can explain the methods used to examine fibers in forensic science. I can describe why fiber analysis is important in the realm of forensic science.

Hair & Fiber Analysis

Can be used to match a suspect with a crime scene Can be microscopically analyzed for similarity Comparisons continue to improve as forensic techniques improve

Part 1 Hair Background Grows from a collection of cells called a follicle The hair shaft is composed of three parts: 1.cuticle – outside covering of hair shaft, can look like overlapping roof shingles

2.Cortex – inside the cuticle, a pigmented layer 3.Medulla – runs down the center of the hair shaft

Many photos can be obtained from hair dressing publications. Many of the following are from this publication.

Hair texture can vary considerably depending upon the ratio of cuticle to medulla

How a hair grows

Hair fibers are excellent for ID study because: They resist decomposition May indicate drug use or poisoning

To distinguish between animal and human hair use a Medullary Index diameter of hair’s medulla Medullary Index = diameter of the hair M.I. = <.33 hair is human M.I. =>.5 or more, hair is animal

Appearance of different hair (or fur) types will vary from animal to animal

Cat hair

Dog hair

Rabbit hair

Other animal hair DeerMuskrat

Deer – no cortex, medulla filled with spheres Mouse – parallel rows of beads

Human Medullary Patterns has three types: Continuous medullary canal Interrupted medulla (regular interruption) Fragmented medulla (interruption irregular)

Hair Photos Can you identify the type of medullary pattern- continuous, interrupted and fragmented?

Caucasoid Oriental Negroid

Hair from different races NegroidMongoloidCaucasoid

Hair cannot be absolutely identified as to race. Traits associated are often and characteristics of races are less distinct.

Some Caucasoid natural colors

Additional Information Individuals of Oriental origin usually have a continuous medulla Dyed hair shows color distributed in cortex and medulla Bleached hair has a yellowish tint As hair grows, natural color returns

Normal hair

Damaged hair BurnedSplit endsRazor cut

Hair is ‘class evidence’ not individual evidence What’s the difference? Varies in texture from one region of the body to another Round or oval in cross-section in Caucasians Oval or flat in cross-section in African Americans

DNA Analysis Only possible if ‘bulb’ at the base of the hair is intact Bulb

Forcibly removed Follicle intactPulled

A Baseline Up to 50 hairs from each body region (head, pubic area, facial hair, etc., are needed to provide a baseline for comparability

Pubic hair

Hair Comparison- Error rates (study done by FBI)  Hair evidence ( ) was DNA tested & microscopic examination  11% of hairs that were “matches” by examiners via microscopes were actually non- matches according to DNA.  Conclusion: Microscopic matches are presumptive in nature and must be confirmed by DNA.

Central Park Jogger Case  5 teens convicted of brutally beating & raping “Central Park Jogger” (1989)  Evidence: confessions by teens & hair on one defendant that “resembled” victim.  Another man came forward & confessed to crime & had matching DNA (2002)

Fiber Analysis  Are considered class evidence (they are very hard to individualize)  Have probative value (can prove something)  common at a crime scene  Analyzed based on physical & chemical properties

Types of Fibers Natural Silk Cotton Wool Cashmere (goats) Synthetic had to learn how to chemically manufacture polymers first) Rayon (1911) Nylon (1939) Acetate Acrylic Spandex Polyester

Natual vs. Synthetic CottonRayon

Individual vs. Class Evidence Individual Evidence Really high probability of being linked to one, unique source Ex: Fingerprints, DNA, Bullets, Tire/ footwear patterns, Tool marks, Broken glass Class Evidence Object has characteristic common to a group of similar objects Ex: Hair, Fibers, Blue jeans Can increase the probability of class evidence by finding things that can make it unique: Ex: stains, wear patterns on jeans

Probability & Class Evidence Product Rule- Used to determine the probability of finding a particular characteristic in a population. Uses probability of each individually occurring and then multiply them together, you can determine the chances of all the characteristics occurring at one time. Increases the probative value of the class evidence. Ex: suspect seen wearing a white tshirt, jeans, and white tennis shoes.

Product Rule Example: Ex: Suspect seen leaving student parking lot where window was broken & ipod stolen. Witness says suspect had: brown hair, wearing white shirt, and jeans. (assume: 1400 students) Brown hair = 70% of students have white fibers = 10 % student have on denim fiber= 20% students wearing How many people should be called in? (.7)(.1)(.2) = or 1.4% of students will be wearing this combination of items. Roughly 20 students/1400.