QM Study Guide Review Forensic Science 2015-2016
Vocabulary Vocabulary: Keratin Neutron activation analysis A type of fibrous protein that makes up the majority of the cortex of a hair Neutron activation analysis A method of analysis that determines the composition of elements in a sample
Hair Shaft Epidermis Dermis Sebaceous Gland Hair follicle Cuticle Cortex Medulla Papilla Capillary
Chapter 3 the formula for calculating medullary index. Diameter of medulla/diameter of hair How is it used to determine an animal hair from a human hair? Animal hair has medullary index of 0.55 or higher Human hair has medullary index around 0.33 Let’s Practice:
Differences between an animal and human hair What are some characteristics that can be studied by looking at a hair and examining it under a microscope? Color, pigment distribution, cuticle scale patterns, medulla patterns, direction of top of hair, if follicular cells are present Differences between an animal and human hair Patterns of pigmentation, the medullary index and the cuticle type.
Rate of growth for a human hair 1.3 cm/month 0.44mm/day How can you use this information to determine an estimated time of death or estimated time of drug use? Divide the length of hair from scalp to area of interest by the rate of growth for an estimated time of drug usage or time of death. Let’s practice… A person was suspected of chronic drug use so a hair was taken to be tested for presence of drugs. The person stated “I stopped using drugs 2 months ago man.” Analysis of the hair revealed traces of THC and cocaine at 2.6cm and beyond all the way to the tip of the hair. Based on these results has the guy been clean or off drugs for 2months? Yes, he has been off drugs for 2 months. Hair grows at an approximate rate of 1.3cm per month and the drugs were not detected in the last 2 months of hair growth or 2.6cm. Evidence 2.6cm/1.3cm = 2 months
Where can DNA be found on hair? Hair follicle or follicular tag What type of evidence is hair classified as? Class evidence, trace evidence, circumstantial evidence If the hair follicle is present and DNA can be extracted it can be used to identify an individual.
Chapter 4 Direct transfer Secondary transfer Synthetic fibers Evidence transferred from one source to another. Secondary transfer Evidence transferred from one source to another and then to another source. Synthetic fibers Made from man made substances such as plastic Natural fibers harvested from plants, animals or mineral sources Yarn Fibers that have been spun together Monomer A mall molecule that may bond to more of the same units to become a polymer
What types of evidence can fibers be classified as? Trace evidence, class evidence and circumstantial evidence What types of information can be learned from fiber evaluation? Type of fiber, fiber color, number of fibers found may suggest the level of violence in the crime, location of fibers, textile type, number of different types of fibers. What major health hazard has asbestos been linked to? Lung cancer How can fiber evidence be used by forensic scientists to help link multiple crimes to a suspect? Fiber evidence can link multiple crimes committed by the same suspect(s) if matching fibers are found at more than one crime scene or more than one victim. Example several serial killers have left behind fiber evidence on the bodies of several of their victims. This evidence along with other similarities among how the crime was committed can be enough to get a confession, or a conviction.