Trace Evidence Part II

Summary Microscopic Analysis Types of Trace Evidence Glass Hair (fur) Fibers Paint Soil Gunshot Residue

Hair What is hair? What crimes are hair involved in? How is hair collected? How is hair analyzed in the lab?

What is hair? Natural fibers of animal origin Trace > Hair What is hair? Natural fibers of animal origin Terms: human = hair; animal = fur Usually growing (live root)

What is hair? Cellular material in the hair shaft (mtDNA) Trace > Hair What is hair? Cellular material in the hair shaft (mtDNA) Good DNA in the hair root for forcibly removed hairs (STR)

What crimes are hairs involved in? Trace > Hair What crimes are hairs involved in? Hairs are shed from people; can link a person to a crime scene. Animal fur may also link a person to a crime scene.

How is hair collected? Visually by hand or with forceps. Trace > Hair How is hair collected? Visually by hand or with forceps. Possibly tape lift. Packaged in sealed containers.

How is hair analyzed? Look at class characteristics (microscope): Trace > Hair How is hair analyzed? Look at class characteristics (microscope): Color Medulla, Cortex, Cuticle

How is hair analyzed? Medulla: Line down middle of hair Trace > Hair How is hair analyzed? Medulla: Line down middle of hair Species ID or human ID Present, absent, or fragmented

How is hair analyzed? Cortex: Color of hair Species ID or human ID Trace > Hair How is hair analyzed? Cortex: Color of hair Species ID or human ID May contain pigment blotches May contain air pockets

How is hair analyzed? Cortex: Humans = 1 color entire length Trace > Hair How is hair analyzed? Cortex: Humans = 1 color entire length Animals = color can vary at root/middle/tip

How is hair analyzed? Cuticle: “Scales” on outside of hair Trace > Hair How is hair analyzed? Cuticle: “Scales” on outside of hair Species ID only Humans = imbricate

How is hair analyzed? (cuticle) Trace > Hair How is hair analyzed? (cuticle) Procedure: Put clear nail polish on slide. Place hair in nail polish; wait to harden. Remove hair; look at indentations in nail polish (microscope).

Fibers Fibers are very useful as trace evidence: Vary widely in class characteristics color, shape, chemical composition, etc. Easily transferred from one source to another (carpets, clothes, etc.) Significant persistence (won’t degrade)

How are fibers used as evidence? Trace > Fibers How are fibers used as evidence? As with other trace evidence, fibers can be transferred to/from a person or objects linking them to one another.

How long do fibers persist? Trace > Fibers How long do fibers persist? Most fiber evidence is lost (fall off) a short time after the transfer occurs. The fibers that do remain will be persistent.

Fibers can be classified into three main categories: Trace > Fibers Fibers can be classified into three main categories: Natural (animal, plant, mineral) Manufactured Synthetic

Natural Fibers: Found in nature Can be artificially colored or treated Trace > Fibers > Natural Natural Fibers: Found in nature Can be artificially colored or treated Cotton Wool Hemp

Animal Fibers Wool - Hairs from sheep Silk - comes from silkworm Trace > Fibers > Natural Animal Fibers Wool - Hairs from sheep Most common of animal fibers Hairs are spun to form thread Silk - comes from silkworm Spun as double filament (separated before use) Because of length, doesn’t shed easily Other Hairs from Animals

Plant Fibers Cotton - seed hairs of cotton plant Trace > Fibers > Natural Plant Fibers Cotton - seed hairs of cotton plant by far most common fiber (find almost everywhere) Under microscope, fibers resemble twisted ribbon

Other Plant Fibers: Linen - stem fiber from flax plant Trace > Fibers > Natural Other Plant Fibers: Linen - stem fiber from flax plant Kapok - from seed hairs of kapok plant Other fibers - Manila, hemp, sisal, jute

Mineral Fibers Asbestos - crystalline material Trace > Fibers > Natural Mineral Fibers Asbestos - crystalline material Used to be used for insulation Fractures into thin rods that can get into your lungs; can kill you Not used much anymore

Filament vs. Staple Filament: Long continuous fiber (like silk) Trace > Fibers Filament vs. Staple Filament: Long continuous fiber (like silk) Staple: Filament is cut into smaller pieces; staples are spun together to form thread (like cotton)

Manufactured Fibers Regenerated Fibers Example: Rayon Trace > Fibers > Manufactured Manufactured Fibers Regenerated Fibers Cellulose is dissolved, then resolidified to form the polymer fiber Can occur in filament or staple form Example: Rayon

Synthetic Fibers Man made Can also be filament or staple Examples: Trace > Fibers > Synthetic Synthetic Fibers Man made Can also be filament or staple Examples: Nylon and Polyester

Synthetic Fibers Acrylics More common as evidence Trace > Fibers > Synthetic Synthetic Fibers Acrylics More common as evidence Usually in staple form Staples spun together, similar to wool

Trace > Fibers > Analysis Begin by identifying and comparing class characteristics for unknown sample (evidence) and known sample. Known Unknown

Fibers from rug in a van. Fibers found on victim. Trace > Fibers > Analysis Fibers from rug in a van. Fibers found on victim.

Class characteristics Trace > Fibers > Analysis Class characteristics Color: microscopic examination Size: length and width can be measured Shape: cross section is viewed

Class characteristics Trace > Fibers > Analysis Class characteristics Refractive Index – n. The ratio of the speed of light in air or in a vacuum to the speed of light in another medium. Other microscopic properties (PLM)

Class characteristics Trace > Fibers > Analysis Class characteristics Chemical Composition: determined by advanced instrumentation

Threads, Yarn, Rope, Cordage Trace > Fibers > Cordage Threads, Yarn, Rope, Cordage Smallest component is fibers (staple) twisted together to form thread or is a filament. This thread can then be twisted with other threads to form a thicker thread (string, etc.) This thicker cord can then be twisted with other thicker cords, etc.

Threads, Yarn, Rope, Cordage Trace > Fibers > Cordage Threads, Yarn, Rope, Cordage Small cords or fibers twisted together to form larger cords At each step, the number of cords can be counted. At each step, the twist direction is either “S” or “Z”

Fiber niso nll n Biref MP (ºC) K1 1.518 to 1.528 1.544 to 1.551 1.505 to 1.516 0.035 to 0.039 Does not melt K2 1.777 to 1.877 2.050 to 2.350 1.641 to 1.646 0.200 to 0.710 K3 1.512 to 1.521 1.510 to 1.520 1.512 to 1.525 -0.001 to -0.005 K4 1.538 to 1.539 1.530 to 1.539 -0.000 to -0.002 192 – 210 K5 1.533 to 1.545 1.568 to 1.583 1.515 to 1.526 0.049 to 0.061 210 – 230 K6 1.540 to 1.541 1.577 to 1.582 0.056 to 0.063 250 – 264 K7 1.522 1.553 1.507 0.046 182 – 186 K8 1.535 to 1.539 1.568 to 1.574 1.518 to 1.522 0.050 to 0.052 133 – 138 K9 1.567 to 1.575 1.632 to 1.642 1.534 to 1.542 0.098 to 0.102 282 – 290 K10 1.474 to 1.478 1.474 to 1.479 1.473 to 1.477 0.002 to 0.005 245 – 260 Q 1.520 1.515 1.513 -0.003

Glass What is glass? What crimes are glass involved in? How is glass collected? How is glass analyzed in the lab?

What is glass? Made from fused inorganic materials Trace > Glass What is glass? Made from fused inorganic materials Amorphus; not crystalline (molecules not arranged) Varies in elemental formula Many shapes and colors

How is glass involved in crime? Trace > Glass How is glass involved in crime? Small fragments can be used as trace evidence (link objects/people) Crime scene reconstruction

Trace > Glass How is glass collected? For reconstruction, detailed photographs can be taken or the entire pane of glass is collected.

Trace > Glass How is glass collected? For trace evidence, usually visually collected with forceps and packaged in plastic bags.

Trace > Glass For reconstruction: Radial cracks Concentric cracks

For reconstruction: Trace > Glass Concentric cracks Radial cracks

Determine the direction of projectile. Trace > Glass For reconstruction: Determine the direction of projectile. When looking at a radial section, conchoidal fractures point back to the origin of the break Core usually on opposite side of the origin

Determine the order of projectiles when dealing with more than one. Trace > Glass For reconstruction: Determine the order of projectiles when dealing with more than one. 2 1 3

Determine the order of projectiles when dealing with more than one. Trace > Glass For reconstruction: Determine the order of projectiles when dealing with more than one. 2 1 3

Trace > Glass For trace analysis: Associate unknown glass found at the crime scene with known samples to determine the source. Done with microscopic analysis Color, curve, thickness, etc. Refractive index: Determined by placing glass in oils of different refractive indexes

Trace > Glass Refractive index: Low relief = no outside line R.I. of glass and oil are similar High relief = thick outside line (Becke line) R.I. of glass and oil are different

Paint What is paint? What crimes are paint involved in? How is paint collected? How is paint analyzed in the lab?

What is paint? Colored chemical coating Covers cars and houses Trace > Paint What is paint? Colored chemical coating Covers cars and houses

What is paint? Paint contains 3 things: Trace > Paint What is paint? Paint contains 3 things: Vehicle – binds components together Pigment – gives paint color Extenders – used to modify gloss, texture, opacity, etc.

What crimes are paint involved in? Trace > Paint What crimes are paint involved in? Hit and Runs – paint from car left at scene Other vehicular accidents Home invasion – windows; on suspect

How is paint collected? Visually by hand or with forceps. Trace > Paint How is paint collected? Visually by hand or with forceps. Packaged in sealed containers.

How is paint analyzed? Possibly a physical match (jigsaw-like) Trace > Paint How is paint analyzed? Possibly a physical match (jigsaw-like) Associate the unknown paint with a known sample (class characteristics)

Chemical composition determined by FT-IR Trace > Paint > Analysis How is paint analyzed? Chemical composition determined by FT-IR Chemical “Fingerprint”

Paint can be in multiple layers Trace > Paint > Analysis Paint can be in multiple layers Each layer is analyzed to determine its physical and chemical properties.

Soil What is soil? What crimes involve soil? How is soil collected? How is soil analyzed in the lab?

What is soil? Mixture of animal and vegetable materials, and minerals Trace > Soil What is soil? Mixture of animal and vegetable materials, and minerals In many ways, soil has a unique composition in a given area.

What crimes involve soil? Trace > Soil What crimes involve soil? Due to the widespread location of soil (earth), it can be used to associate people, objects, and scenes in numerous cases.

How is soil collected & analyzed? Trace > Soil How is soil collected & analyzed? Collected in jars or vials. Materials in soil are identified and quantified. Analysis relies on soil composition being: Consistent over time in one location Different in different locations

Gun Shot Residue (GSR) What is gun shot residue (GSR)? What crimes are GSR involved in? How is GSR collected? How is GSR analyzed in the lab?

Trace > Gun Shot Residue What is GSR? Mixture of materials that originate from the firing of a gun. From the chamber From the barrel

What is GSR? GSR will fall onto hands of person firing the gun. Trace > Gun Shot Residue What is GSR? GSR will fall onto hands of person firing the gun.

What crime is GSR involved in? Trace > Gun Shot Residue What crime is GSR involved in? Crimes with guns

How is GSR collected & analyzed? Trace > Gun Shot Residue How is GSR collected & analyzed? Hand/glove/paw is swabbed Analysis: Elements barium and antimony are found in high levels. Use powerful microscopy (SEM) Use chemical tests (color change reactions)