Statistical Significance of Evidence in Wayne William case: Forensic experts found 28 different pieces of microscopic evidence (dog hairs, various fibers)

Yellow-green carpet fiber: This fiber found on several victims had been made and sold to various carpet manufacturers from 1970 to 1971. During this period approximately 16,397 square meters of carpet were sold in the southern U.S.

The fibers were manufactured by the Wellman Corp sold during 1967-74 sold undyed to other companies. West Point Pepperell Corp, of Georgia, made Luxaire carpet in English Olive green- only between 1970-1971

Calculate the following: It was estimated that 82 average sized rooms in the state of Georgia had this carpeting. Since there were 638,995 houses in the Atlanta area, what is the probability of a house having this type of carpet? 1 out of __________ or ________%

Only about 16,000 yd2 were sold The odds were 1 in 7,792 now. (out of 16 billion yd2 total) only 82 homes in Georgia should have that same carpet, ten years later. The odds were 1 in 7,792 now. BUT, Jimmy Ray Payne (killed a month earlier) had fibers that also matched carpets in the Williams’ car! This was a 1 in 3828 odds. SO- the odds of both fibers found on victims matching Wayne Williams’ carpeting was 1 in 30 million!

What this proved: The carpet in the William’s home was quite uncommon, thus finding one of these fibers on a victim made it highly probable that the victim had been in contact with Williams. In this case, the presentation of statistical data was as important as the data itself.

Verdict The jury found Wayne Williams guilty of two counts of murder in the first degree (Police suspected that Williams killed up to 28 males, but the prosecution focused on the last two found in the Chattahoochee river). Wayne Williams is currently serving two life sentences

Fiber Evidence A fiber the smallest unit of a textile material that has a length many times greater than its diameter. can be spun with other fibers to form a yarn that can be woven or knitted to form a fabric. Transfer of fibers and the significance of fiber associations are affected by: The type and length of fiber used the type of spinning method the type of fabric construction http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidence

Matching unique fibers on the clothing of a victim to fibers on a suspect’s clothing can be very helpful to an investigation whereas the matching of common fibers such as white cotton or blue denim fibers would be less helpful. The discovery of cross transfers and multiple fiber transfers between the suspect's clothing and the victim's clothing dramatically increases the likelihood that these two individuals had physical contact.

the smallest unit of a textile material that has a length many times greater than its diameter. can occur naturally as plant and animal fibers, but they can also be man-made. can be spun with other fibers to form a yarn that can be woven or knitted to form a fabric. Transfer and significance of fibers type and length spinning method construction

Fiber Evidence Fibers are gathered at a crime scene with tweezers, tape, or a vacuum.  They generally come from clothing, drapery, wigs, carpeting, furniture, and blankets.  For analysis, they are first determined to be natural manufactured mix of both

Natural Fibers Many different natural fibers that come from plants and animals are used in the production of fabric. Cotton fibers are the plant fibers most commonly used in textile materials The animal fiber most frequently used in the production of textile materials is wool, and the most common wool fibers originate from sheep. http://www.fireflydiapers.com/articles/diaperarticle_naturalfibersabsorb.htm

Synthetic Fibers More than half of all fibers used in the production of textile materials are synthetic or man-made. Nylon, rayon, and polyester are all examples of synthetic fibers. Fibers under a microscope Cross-section of a man-made fiber Images: http://www.trashforteaching.org/phpstore/product_images/YarnWS.JPG http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidence http://www.jivepuppi.com/images/fiber_evidence.jpg

Types of Fibers Synthetic Natural Rayon Nylon Acetate Acrylic Spandex Polyester Natural Silk Cotton Wool Mohair Cashmere

Fiber Comparison Can you tell the difference(s) between the cotton on the left and the rayon on the right?

Protein Fibers Wool—animal fiber coming most often from sheep, but may be goat (mohair), rabbit (angora), camel, alpaca, llama, vicuna Silk—insect fiber that is spun by a silk worm to make its cocoon; fiber reflects light and has insulating properties

Mineral Fibers Asbestos—a natural fiber that has been used in fire-resistant substances Rock wool—a manufactured mineral fiber Fiberglass—a manufactured inorganic fiber

Synthetic Fibers (Made from derivatives of petroleum, coal and natural gas) Nylon—most durable of man-made fibers; extremely light weight Polyester—most widely used man-made fiber Acrylic—provides warmth from a lightweight, soft and resilient fiber Spandex—extreme elastic properties

Polymers Synthetic fibers are made of polymers which are long chains of repeating chemical units. The word polymer means many (poly), units (mer). The repeating units of a polymer are called monomers.

Steps of Fiber Analysis Bag clothing items individually in paper bags. Make sure that different items are not placed on the same surface before being bagged. Make tape lifts of exposed skin areas of bodies and any inanimate objects Removed fibers should be folded into a small sheet of paper and stored in a paper bag.

The first step in fiber analysis is to compare color and diameter.  Microscopic observation Burning—observation of how a fiber burns, the odor, color of flame, smoke and the appearance of the residue Thermal decomposition—gently heating to break down the fiber to the basic monomers Chemical tests—solubility and decomposition

Microscopy Fibers should be first examined with a stereomicroscope. Physical features such as: crimp, length, color, relative diameter, luster, apparent cross section, damage, and adhering debris should be noted. Fibers are then tentatively classified into broad groups synthetic, natural, or inorganic. If the sample contains yarns, threads, or sections of fabric, construction should be recorded

The Scanning Electron Microscope (SEM) bombards a specimen with a beam of electrons instead of light Produces a highly magnified image from 100x to 100,0000 Depth of focus 300X better than optical systems at similar magnification

Bombardment of the specimen’s surface with electrons Produces x-ray emissions Characterize elements present in the material under investigation

Dental Plaque

Bread Mold Aspergillus sp.)

Penecillium sp.

SEM: Hair and Hair follocles

SEM: hafnium nitride interface coating on carbon fibers

Dust Mite Family Reunion

PBS video about FBI needing to revise http://video. pbs PBS video about FBI needing to revise http://video.pbs.org/video/2255300469/ CSI school: http://www.youtube.com/watch?v=BjLHW7qQEl0 NCSSM analysis video http://www.youtube.com/watch?v=e3ZlA5GoFVw