What two morphological characteristics does a criminalist first compare when examining fibers with a microscope? What other features may be important in such a comparison? Color and diameter. Striations (lined markings) , and the cross-sectional shape of the fiber.
What two aspects of hair morphology are most useful in species determination?
So the most useful characteristics for species determination by forensic analysis turned out to be the pigmentation of the cortex, the characteristics of the medulla and its medullary index .
What are the 3 primary characteristics of hair that are studied by forensics?
Hair viewed for forensic investigations is studied both macroscopically and microscopically . Length, color, and curliness are macroscopic characteristics. Microscopic characteristics include the pattern of the medulla, pigmentation of the cortex, and types of scales on the cuticle (Figure 3-12).
What are some of the morphological features used to compare fibers?
Other morphological features that could be important in comparing fibers are: ... * Cross-sectional shape of the fiber . Characteristics of Fibers. Color, diameter, birefringence, shape, presence or absence of delustering particles.
What are the 2 other uses of hair evidence in a criminal case?
In a criminal investigation, finding biological evidence such as hair proves helpful in establishing the scope of the crime scene, connecting a suspect to a weapon or the crime scene, supporting witness statements , or even connecting different crime scene areas.
What analytical technique does a criminalist?
What analytical technique does a criminalist use to analyze the composition of the dye in a fiber? Chromatographic separation of the dye constituents . Describe three analytical techniques for comparing the color of two fibers.
What characteristics can be used to identify hair samples?
A number of microscopic characteristics associated with the cuticle are used in a hair comparison. The thickness of the cuticle, the variation in the thickness, the presence of pigment, and the color are all useful characteristics.
What kind of characteristics were used to identify if two hairs came from the same individual?
Microscopic comparison of hair collected from two different places is used to determine if the hairs are from the same person or animal. Because hair can be moved from location to location by physical contact, the presence of a specific person’s hair can link a suspect or a victim to a crime scene.
What is the hairs most characteristic forensic feature?
what remains the hair’s most characteristic forensic feature? ... Cuticle — outer covering of hair consisiting of scales that come in 3 shapes: imbricate, coronel, and spinous.
Which characteristic of hair is most important?
Each hair type has its own shape and characteristics. The appearance of the tip of the hair shaft is an important comparative characteristic.
What are the two most common types of man made fibers?
There are two types of man-made fibres – synthetic fibres and regenerated fibres . Regenerated fibres are made from cellulose polymers that occur naturally in plants such as cotton, wood, hemp and flax. Materials like rayon and acetate two of the first man made fibres to be produced were made from cellulose polymers.
What are the different characteristics of a fiber filament and fabric?
What are the different characteristics of a fiber, filament, and fabric? A filament is a single strand of material; a fiber is many filaments twisted together; fabric is many fibers woven to make a textile . A gray cotton fiber was found on the red sweater of a victim.
What are two features that make hair a good subject for establishing identity?
Two of the features that make hair a good subject for establishing individual identity are its resistance to chemical decomposition and its ability to retain structural features over a long period of time . Much of this resistance and stability is attributed to the cuticle or outside covering of the hair.
What characteristic makes hair a useful forensic tool?
What characteristics make a hair a useful forensic tool? The color, the unique patterns, and textures and the opportunity to get DNA all help forensics analysis identify suspects.
What is meant by morphology of hair?
Morphology and Structure of Human Hair. – Hair consists of dead cells which are extruded from the base of the follicle . – Hair consist of two parts; the shaft, the root or follicle. The hair is formed by cells of the dermal papilla at the base of the follicle.
What type of evidence is hair?
Hair is considered class evidence when the follicle is not attached because the follicle is the part that contains DNA. When the follicle is attached, it is considered individual evidence.
What equipment does a criminalist use?
The criminalist uses a battery of analytical tools and their knowledge of chemistry to identify controlled substances in powders, pills, liquids, and body fluids. A criminalist may be called to a clandestine laboratory by investigators, where illegal drugs are produced.
What are the characteristics of hair?
- texture. the size or diameter of the hair shaft. ...
- porosity. The ability of hair to absorb and hold moisture and liquid. ...
- tenacity. the degree of difficulty with which the cuticle can be penetrated. ...
- density. -the quality of number of hairs per square inch on the scalp. ...
- elasticity.
What is the focus of criminalistics?
The main goal of criminalistics is to apply the principles of sciences to the examination of evidence in order to help the justice system determine that a crime has been committed, to identify its victim(s) and perpetrators, and finally, determine the modus operandi, or method of operation .
What is the role of a criminalist?
Criminalists cover a broad range of criminal justice jobs within the forensic science field that examine physical evidence to link crime scenes with victims and offenders . ... These criminalists consult with experts, examine and analyze a variety of evidence including fingerprints, hair, fibers, skin, blood, and more.
What are chemical properties of hair?
The overall chemical composition of hair is 45 % carbon, 28 % oxygen, 15 % nitrogen, 7 % hydrogen and 5 % sulphur . The hair shaft is essentially composed of keratin. Hair keratin is hard, compact and strong. This fibrous protein is gradually formed inside cells from the germinal layer.
Is human hair Hollow?
The unique coaxial structure of human hair, composed of medulla, cortex, and cuticle, resulted in a hollow structure of carbon fibers through pyrolysis.
What is the importance of comparing two different samples of hair in forensic examinations?
Hair samples are one of the most important resources in the forensic analysis of crime scenes , often providing valuable information that can help to lead to the identification of a suspect or victim.
Do all hairs from the same person have the same microscopic characteristics?
The basic morphology of human hairs is shared by each individual in the population , but the arrangement, distribution, and appearance of individual microscopic characteristics within different regions of hair routinely allow a skilled hair examiner to differentiate hairs between individuals.
What are the 2 steps in the process of identifying hair with a light microscope?
Hair Microscopy
Examination of human hairs in the forensic laboratory is typically conducted through the use of light microscopy. Two-step process— the identification of questioned hairs and the comparison of questioned and known hairs using comparison microscopy .
Do fibers have cuticles?
With fiber, the cuticle is the outer layer of the hair which consists of dead cells that overlap in layers that form scales. The scales are uni-directional, point away from the skin and provide strength and structure around the shaft of the fiber.
What two types of hair are found in most animals?
One of the distinguishing characteristics of mammals is the protective growth known as hair. Two major kinds of hair provide either protection (guard hairs) or insulation (underfur) .
Which race has the most hair on their head?
Caucasians have the most dense hair. Blondes have more strands on their scalp – about 146,000 hairs. The black-haired have about 110,000 hairs, brunettes 100,000 and redheads about 86,000. In spite of the density, genetic hair loss is highly prevalent in this race.
Are all hairs identical?
Hair is composed of a protein called cellulose. All hairs on the head of a person are identical . The cortex may contain pigment granules.
Can you distinguish a hair that has been bleached or dyed from a natural hair explain?
Can you distinguish a hair that has been bleached or dyed from a natural hair? ... If the hair has been dyed or colored, it shows a smooth uniform look . Naturally-colored hair has granules that have a similar texture to a crayon.
What does the cortex do in hair?
The cortex forms the main bulk and pigment (colour) of your hair . It consists of long keratin filaments, which are held together by disulphide and hydrogen bonds. The health of your cortex depends largely on the integrity of the cuticle protecting it.
What aspects of the hairs are criminalist particularly interested in matching?
When comparing strands of hair, the criminalist is particularly interested in matching the color, length, and diameter . Other important features for comparing hair are the presence or absence of a medulla and the distrib- ution, shape, and color intensity of pigment granules in the cortex.
Does hair consist of two parts?
Hair is a derivative of the epidermis and consists of two distinct parts: the follicle and the hair shaft . The follicle is the essential unit for the generation of hair. The hair shaft consists of a cortex and cuticle cells, and a medulla for some types of hairs.
What are the characteristics of man-made Fibres?
- Luxurious feel and appearance.
- A wide range of colors and lusters.
- Excellent drapability and softness.
- Relatively fast-drying.
- Shrink-, moth-, and mildew-resistant.
What are the two categories of synthetic fibers?
- Rayon.
- Nylon.
- Polyester.
- Acrylic.
What are the two groups of synthetic fibers?
Polyamides and polyesters are two groups of synthetic fibres with high strength, not easily stretched and used as textile. Nylon is an example of polyamide polymers. Terylene is an example of polyester polymers. Nylon and terylene are produced through condensation polymerisation.
What are the different characteristics of a fiber?
- Strong.
- Crisp, soft hand.
- Resistant to stretching and shrinkage.
- Washable or dry-cleanable.
- Quick drying.
- Resilient, wrinkle resistant, excellent pleat retention (if heat set)
- Abrasion resistant.
- Resistant to most chemicals.
What different characteristics of a fiber do forensic scientists identify?
Fibers as Evidence
Fibers can be compared to specific sources, such as pieces of clothing and vehicles, to see if they match. The fiber’s type, color, and even its texture are all helpful in identifying the origin of the fiber. Fibers can also help determine whether physical contact occurred.
What are the characteristics of fibers observed in the lab that can be analyzed?
These types of fibers can be readily distinguished from animal fibers in that they have no medulla or scale pattern. When examining fiber evidence, characteristics such as fiber type, shape, diameter, color, variation of color in the fiber, length of fiber, and lengthwise striations on the fiber’s surface are noted.
What analytical technique does a criminalist?
What analytical technique does a criminalist use to analyze the composition of the dye in a fiber? Chromatographic separation of the dye constituents . Describe three analytical techniques for comparing the color of two fibers.
What is the hairs most characteristic forensic feature?
what remains the hair’s most characteristic forensic feature? ... Cuticle — outer covering of hair consisiting of scales that come in 3 shapes: imbricate, coronel, and spinous.
What is the MI of a dog could such hair be confused with human hair if so could it definitely be differentiated from human reason out your answers?
Usually animal hair has an M.I. greater than 33, so this could be construed as human; it can be differentiated by the cuticle . The medulla is found on the interior of the hair; it may be continuous, fragmented, or absent. The cuticle is found on the outside of the hair shaft; it has a scale pattern.
