Forensics Study Guide Unit 1

Professions

Forensic Anthropologist- Assist with human remains(bones). Can assist in determining time of death, damages and establishes biological information

\
Document Examination Unit- studies the handwriting and typewriting on questioned documents to determine  authenticity and/or source(white collar crimes)

\
Forensic Odontologist- identifies and compares dental evidence in criminal cases

\
Forensic Entomologist- Examines bugs near/on/in the body to tell the stages of decomp.

\
Toxicologist- Analyze a person's body to determine if various substances are present.  They do this to tell: if judgment was impaired, altered behavior and if it contributed to cause of death

\
Firearms examiner- A firearm examiner examines different firearms, weapons, bullets, and other criminal investigations. They also collect physical evidence at crime scenes and testify in court explaining the results of the examination.

\
Fingerprint analyst- ACE-V(analyze,compare, evaluate, verify) finger prints, hand prints etc. preserve them and take samples

\
Forensic Serology- Processes, Compare, and/or identify biological Evidence in a crime case. Determines if samples are human or non-human

\
Forensic  Psychiatrist or Psychologist- They interview suspects and analyze the answers from the interviews. They use their extensive knowledge of human psychology to determine whether or not a suspect is suffering from mental illness and if they are mentally fit to stand trial

\
Forensic Botanist- Help law enforcement officers analyze plant materials at a crime scene

\
Forensic Pathologist (Medical Examiner)- A medical doctor who performs the autopsy on a victim to determine cause of death, manner of death, and approximate time of death

\
Forensic Engineer- main role is to find the cause of failures in structures,show how to make improvements, and aid in legal proceedings.

\
Computer Forensic Technician- Use different techniques to find and store information from electronic devices and data recovery.

Forensic Artist- A professional responsible for facial reconstruction or the sketching of a crime scene, recreates face with skulls

\
Forensic Trace Evidence Analyst- Identifies hairs/fibers and finds traits within them to link it to crimes and suspects.

\
HAIRS AND FIBERS

• It’s more resistant to decomposition than body tissues.(It can hold up for several years)
• Hair is made of keratin, which is a very strong protein
• Each species of animal possesses hair with characteristic length, color, shape, root appearance, and internal microscopic features that distinguish one animal from another.
• Within the Human body there is variability within hair

Follicle

• part of the skin where hair is grown
• this part of the hair is alive; DNA can be found here
• humans develop hair follicles during fetal development
• no new follicles are produced after birth

\
Hair Shaft

Hair shaft has three layers:

Medulla

• Central core of cells  (inside)
• They can look different in each person(broken,continuous,hollow, dark/light ect)

Cortex

• Thickest layer containing most of the pigment which gives hair its color
• Distribution of pigment varies from person to person
• Pigment is denser near the cuticle

Cuticle

• Outermost layer
• Made of overlapping scales that protect the inner layers (shaft) of hair

Animal Hair(fur) and Human Hair

• Pigmentation in animal hair is denser toward the medulla.
• Pigmentation in human hair is denser toward the cuticle.
• Animal hair can abruptly change colors in a banded pattern.  Human hair can’t.
• The medulla is much thicker in animal hair than human hair.
• The hair shaft (cuticle) differs:
• Cuticle scales in animals tend to resemble petals (spinous)or they give the appearance of a stack of crowns (coronal)
• Cuticle scales in humans commonly are flattened and narrow (imbricate)

SPINOUS                 Coronal                IMBRICATE

\
\
\
TYPES OF HAIR

Cross section of hair:

• Circular
• Triangular
• Irregular
• Flattened which influences the curl

HAIR COLLECTION

• Hairs can be recovered from items using a number of different techniques.
• Some of the methods used to collect hairs from clothing and bedding items are scraping, shaking, taping and picking.
• Debris from large carpeted surfaces might be vacuumed into a filtered canister.
• If the specific location of a hair on a clothing item is important, it might be necessary to pick off the hair or tape the item and record where the hair was removed.
• Head hairs and pubic hairs exhibit a greater range of microscopic characteristics than other human hairs; therefore, head and pubic hairs are routinely forensically compared.
• Twenty-five randomly selected head hairs are generally considered adequate to represent the range of hair characteristics of that individual.
• It is recommended that the same number of hairs be collected from the pubic region.

FIBERS

• Fibers often fall off and are picked up during normal activities.
• Very small fibers are easily shed from most textiles and can become trace evidence
• In an investigation, collection of fibers within 24 hours is critical.
• Fiber evaluation can show such things as the type of fiber, its color, the possibility of violence, location of suspects, and point of origin.

SAMPLES and TESTING

• Weaving spun fibers (yarns) together produces clothing and many textiles.
• Most common form of fiber transfer is from the shedding of an article of clothing or textile.
• An ordinary microscope can be used to find characteristic shapes and markings on natural fibers.
• Infrared spectroscopy can reveal something of the chemical structure of other fibers, that otherwise, may look very much alike.  
• If a large quantity of fibers is found, some can be subjected to destructive tests such as burning them in a flame (see analysis key) or dissolving them in various liquids.
• Crimes can be solved in this way by comparing fibers found on different suspects with those found at the crime scene.

FIBER CLASSIFICATIONS

NATURAL

Wool-Sheep: Cashmere/mohair-Goats

Angora-Rabbits:/Hair-Alpaca/Llama/Camels: Shimmering Silk-Caterpillar

Plant Fibers(polymer cellulose)

• Can absorb water but insoluble
• Very resistant to chemical damage
• Dissolved by strong acids
• Cotton is common

Mineral Fibers

• Fiberglass is a fibrous form of glass
• Asbestos is a natural occuring mineral with a crystalline structure.

SYNTHETIC FIBERS

• Until the nineteenth century, only plant and animal fibers were used to make clothes and textiles
• Half the products used today are artificially produced

Types

• Rayon
• Acetate
• Nylon
• Acrylics
• Polyester

LOCARD PRINCIPLE-the perpetrator of a crime will bring something into the crime scene and leave with something from it,

SENSES

HEARING

The two main roles of the ear in sensory perception is sound detection and maintenance of equilibrium

Tympanic membrane(Ear drum) This receives sound waves and transfers it to ear bones

Auditory Bones(Malleus, incus, stapes) Conduct the sound waves to the oval window

Cochlea-Sense of hearing and participates in auditory transduction

The loudness of sound is determined by the velocity of the vibration of the soundwave.

VISON

Rods and Cones are located on the retina except the optic nerve

Rods take in black and white images and night vision

Cones is the ability to take in colors

The blind spot is where the optic nerve enters the eye, there are no rods/cones in this area.

\
TASTE/SMELL

The 5 main tastes are salty, sweet, bitter, sour, umami

Smell and Taste are so closely related due to they are both dependent on chemoreceptors

Chemoreceptors-They detect different chemical molecules in substances

There can be a great connection between taste and smell. You can smell something and then taste it.

Chemoreceptors are located on the nasal cavity, tongue, soft palate, pharynx, and epiglottis

Taste and smell is when the right chemical hits the right chemoreceptors

TOUCH

The 3 mechanoreceptors are

• Free nerve endings(sensitive to light touch, service of skin)
• Meissner Corpuscles(sensitive to light touch, service of skin)
• Pacinian Corpuscles(heavy pressure and deep in skin)

Mechanoreceptors are what creates touch and are dependent on them

These are responsive to mechanical stimuli aka pressure and gravity

Thermoreceptors are how we feel temperature  and there are three types

• Heat Receptors(25-45C)
• Cold receptors(10-20C)
• Pain receptors(>45 and <10C)

SENSORY ADAPTATION

• The first is that the receptor itself has adapted to the stimuli and stops transmitting the signal to the brain
• The second way is that the lower parts of the brain adapt to the information being received and decide that the information is not important enough to relay to the areas of the brain where you would be consciously aware of the sensation
• Continuous stimulation of the receptors cells, at a constant level results in a sensory adaptation
• A large increase of these stimuli can result in the stimulus coming back.

EYE-WITNESS TESTIMONY

• Testimonial evidence includes oral or written statements given to police as well as testimony in court by people who witnessed an event.
• They have an important outcome of the trial but can be extremely inaccurate
• People can perceive the same situation in many different ways
• 75% of the convictions are overturned through DNA evidence

WITNESS FACTORS

-Age of the Witness- there can be mistaken identities

- Race of Witness- The cross race effect can cause people of the same race to recognize and remember each other faces together

- Drug or Alcohol usage at the time of crime

- Other people-  Can be influenced by other witnesses, investigators, and/or the media.

CRIME SCENE FACTORS/SUSPECT FACTORS

-Extremely traumatic scene(An suspect confronted with a weapon may focus more on the weapon than the suspect)

-Timing(How long you see a suspect matters for how you remember it)

-Facial Features(You’re more likely to remember someone with facial piercings or tattoos)

- Time or Day/View of Scene(The night/day can impact your own vision or from what perspective you see the crime take place)

FACIAL COMPOSITES

Investigators work with sketch artists and eyewitnesses to create facial composites, or sketches of a person’s face.  Today many police departments are using facial reconstruction software to help them with this task.

• Externally circulated local or national media
• Internally through police stations

CHANGE BLINDNESS

• Change blindness is a failure to detect that an object has moved or disappeared.
• There is simply too much information for your brain to process everything that’s going on around you at once.
• Our expectations for what should happen in the environment can play a role in what we notice about the world.

\