VI.+Trace+Evidence


 * __ Trace Evidence __**
 * Hair **
 * Most common type of trace evidence to be found.

Structure of Hair
 * Hair is a part of the skin which grows out of an organ known as the hair follicle.
 * Hair growth begins in the root and extends into the shaft which is comprised of three layers.

1) The Cuticle - 2) The Cortex - 3) The Medulla -
 * Scale structure which provides a protective coating for the hair.
 * It is strong and resistant to chemical decomposition.
 * The cuticle is not useful in identifying individual human hairs but can be a good indicator for distinguishing between human and animal hair.
 * The scale pattern can be looked at under a compound microscope or by placing the hair on a medium such as clear nail polish and when it has dried and hardened the hair is removed and what is left is a clear impression of the cuticle which can be looked at under the microscope.
 * Main body of the hair shaft which is contained within the layer of the cuticle.
 * Composed of spindle-shaped cells that are parallel to the length of the hair.
 * In the cortex are pigment granules which are important because they give the hair its colour.
 * The shape, colour, amount of pigment granules are important for the comparison of hair samples of different people.
 * Collection of cells that resembles a canal which runs through the middle of the hair.
 * The medulla is different in animals and humans, in animals it may be predominant and occupy more than half of the hair’s diameter.
 * The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft.
 * The medulla is not necessarily present in every hair and can vary in appearance.
 * It can be classified as continuous, interrupted, fragmented or absent.

The Root 1) Anagen Phase - 2) Catagen Phase - 3) Telogen Phase - Collection of Hair Evidence
 *  This is where DNA can be found.
 *  The root of a hair can distinguish whether the hair has been pulled out or has been shed naturally.
 *  Hair grows in three stages: anagen, catagen, and telogen phase.
 *  First stage of hair growth
 *  Hair follicle actively produces hair, with the root attached to the hair follicle.
 *  The follicular tag on the hair is important in the anagen phase because it contains DNA for individualizing the hair.
 *  This phase lasts from two to three weeks
 *  Hair growth continues but at a slower rate
 *  Roots become elongated as the root bulb is shrinking and pushed out of the hair follicle
 *  Occurs once the hair growth is complete.
 *  The root takes on a club-shaped appearance
 *  Between two to six months, hair is pushed out of the hair follicle and can now be shed naturally.
 * The examination of hair is often used to distinguish whether it is from a human or animal or to figure out if the human hair sample found at a crime scene relates to a reference sample.
 * The scale structure of the cuticle, medullary index and medullary shape are most important when dealing with hair identification.
 * When comparing human hair, the colour, length and diameter are often the most important
 * Hair samples must be submitted with reference samples from the victim of the crime and the suspect.
 * Reference samples must come from the same area in which the sample is taken. For example, from the head or other parts of the body.
 * The entire hair must be taken for analysis.


 * Fiber Evidence **
 *  Important in incidents that involve personal contact such as assaults or homicides.
 * Fibers can be classified by two groups: natural fibers and manufactured fibers.

1) Natural Fibers
 *  Animal and plant sources
 *  Comparison and identification of natural fibers are done with a microscopic examination of colour and morphological characteristics.
 *  Cotton is natural fiber that is the most common.

2) Manufactured Fibers Examination of Fiber Evidence
 *  Derived from natural or synthetic polymers
 *  Regenerated fibers are produced from regenerated cellulose, examples include rayon and acetate.
 *  Most manufactured fibres are produced from synthetic chemicals and are called synthetic fibers. Examples include polyester and nylon.
 *  First and most important step is the comparison of colour and diameter using a microscope.
 *  Other features that are important for comparing fibers are striations on the surface, presence of delustering particles and the cross-sectional shape of a fiber.
 *  The microspectrophotometer is one way that colours of fibers can by analyzed.
 *  Infrared microspectrophotometer is used to identify the composition of fibers.

Collection of Fiber Evidence Forensics Trace evidence, such as fibers, is useful in connecting people, places, and things with one another. Whether that’s determining where a victim was prior to death, or even what type of rope was used to physically commit the murder? Fiber trace can be extremely helpful in recreating the events of that day. There are a few test that fibers can be subjected to, to determine individually.
 *  Items of clothing which may have traces of fiber evidence should be packed separately in paper bags in order to avoid the cross-contamination of evidence.
 *  Special care should be taken to protect the areas of surfaces which may contain fiber evidence by playing sheets of polyethylene to protect the evidence.
 * Special care also must be taken to make sure that fiber evidence does not come in contact with fibers collected from other objects.

The first is ** Microscopic Comparison **, which looks at the colour & diameter characteristics of the fiber being examined. Other morpological features can include lengthwise striations on the surface of the fiber, cross-sectional shape of the fiber, or even compositional differences in the hues. The ** microspecrophotometer, ** which is a spectrophotometer along with a light microscope, analyzes the visible absorption of light using the light spectrum.

** Spectrometry ** is the measure of the quantity of radiation that a particular material absorbs as a function of wavelength and frequency. The ** spectrophotometer ** measures and records the absorption spectrum of a chemical substance. It measures the wavelength of the fiber dye composition.

** Chromotography ** is a means of separating and identifying the components of a mixture, such as the components that compose a fiber. It’s major premise is that chemical substances have a tendency to partially escape into the surrounding environment when dissolved in a liquid or when absorbed on a solid surface, which is known as the ** Moving Phase ** and the ** Stationary Phase. **  ** Gas Chromatography ** is when a sample substance is dissolved in solvent. It uses the ** Moving Phase, ** which is the carrier gas, to move the substance along the coil. As well as the ** Stationary Phase ** a thin film of liquid within the coil along with the carrier gas. A coiled glass tube is used allowing for the maximum amount of length in a smaller amount of space. Within the coil there is a separation of the substances, and at the end of the coil there is a detector that records the amounts of separated components, which is called a Chromatograph. To determine the class of a fiber you would use ** Infrared Spectrophotometry **. The polymers that compose a manufactured fiber, just as in any other organic substance, selectively absorb infrared light in a characteristic pattern. It provides a reliable method for identifying the genetic class, and in some cases the subclass, of fibers.


 * Soil Evidence **
 *  As with other trace evidence, soil evidence must be carefully collected and compared to soil samples from the crime scene it is taken from and areas near by.
 *  Soils can be distinguished by their appearance.
 *  Comparison of soil samples must be done in the laboratory and the samples must be dried out in the exact same way.
 *  Comparing the colour of the soil is the first step in the forensic examination of soil.
 *  By using a microscope to compare soil samples, the different minerals and rocks present can help distinguish the comparisons of the samples.

Collection of Soil Evidence
 *  Various collections of soil must be collected at the crime scene, most often at 100-yard intervals for reference samples to be compared with the soil sample in question.
 *  One or two tablespoons should be collected and packaged separately in individual containers like plastic vials and should be labelled accordingly.
 *  Evidence that is found on the suspect must be preserved by packaging the object as a whole instead of trying to remove it.

Forensics: Soil analysis can be useful in placing an object or person in a certain location. In the case of Clifford Olson, he frequently dumped his victim’s bodies in rural areas, allowing for soils to embed themselves in his shoes, tires, and on victim’s bodies.

** Mass spectrometry ** is a technique used for measuring the molecular weight and determining the molecular formula of an organic compound, soil being one of many organic compounds. The Mass Spectrometer separates components by using a beam of high-energy electrons, which produces ions that are unstable with excess energy. With the decomposition of ions, which are called the “Fingerprint” of test substances, electric or magnetic fields separate fragments based on their molecular mass.