[2015] Ekta Patel (IMS Grade 7 SFMandell, IMS GRADE 8 SFMandell): Forensic Science (cont.)

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by WoodbridgeGT
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[2015] Ekta Patel (IMS Grade 7 SFMandell, IMS GRADE 8 SFMandell): Forensic Science (cont.)

Forensic Science(cont.)

Testimonial evidence is the evidence provided from an eyewitness. The eyewitnesses give oral or written statements about the event and testimony in court. Eyewitnesses can be a useful tool, but not entirely reliable. Eyewitnesses can also heavily influence the result of an investigation or trial. Eyewitnesses also help create facial composites. Software programs, such as FACE, are used to help the eyewitnesses create the facial composites. These composites are used internally to help investigators solve the crime or externally to the public to receive leads from the public. There are many witness factors that can affect the statement given. Age may play a role in the accuracy of a statement or identification of a suspect, the race of the witness can play a role and so can the use of drugs, as it can alter a person’s ability to recall the events of a crime even after they are no longer under the influence. Other witnesses, investigators, the media, etc. may also influence the witness’ memory.


Hair is composed of keratin, the primary component of fingernails and toenails. Pigments, chemical compounds that reflect certain wavelengths of visible light, results in hair color. Genes influence hair shape and texture heavily. In order to test hair evidence for DNA, the root of the hair must be present. The three different parts in the strands of hair are the cuticle, cortex, and medulla. The cuticle varies on certain circumstances; such as its scales, texture, and presence of pigment. The cortex varies in thickness, texture, and color and the medulla may vary in thickness, continuity, and opacity. Fiber is a type of fabric found at crime scenes and on victims’ bodies. Matching unique fibers on the clothing of a victim to fibers on a suspect’s clothing can be very helpful to an investigation, whereas the matching of common fibers would be less helpful. The discovery of cross transfers and multiple fiber transfers between the suspect’s clothing and the victim’s clothing dramatically increases the likelihood that these two individuals had physical contact.

Impression evidence is created when one object is pressed against another material with enough force to leave an impression of the object. Examples of impression evidence is shoeprints, tool marks, tire tracks, bite mark, and marks on a fired bullet. Impressions may be found in or many different types of materials. The quality of the impression depends on the object making the impression and the surface conditions, such as how hard or soft it is and what type of material it is. Investigators analyze the impression evidence to find unique characteristics to link shoes, tires, tools, and other objects found in a suspect’s possession to evidence at a crime scene. 2-D impression is documented using photography. 3-D impression is documented using photography and casting.

Latent prints are impressions left by friction ridge skin on a surface. Prints may be collected by revealing them with a dusting of black powder and then lifted with a piece of clear tape. Some investigators use fluorescent powder and UV lights to help them find latent prints on multi-colored or dark surfaces at a crime scene to examine them and find out who left the fingerprint. Magnetic powder also can reveal a latent print. This powder works better than black powder on shiny surfaces or plastic. The cyanoacrylate fuming method is a process that is used to develop latent prints on a variety of different objects. Ninhydrin is a chemical that bonds with the amino acids in fingerprints and will produce a blue or purple color and is used to lift prints from surfaces such as paper and cardboard.




Impressive Evidence

Latent Prints

A forensic scientist investigates skeletons. The things investigators want to know about a skeleton to solve a crime us the sex, age, stature, and race. Skulls are most useful when examining a skeleton as they display sex, teeth, age, etc. Sex is determined by examine the skull, pelvis, humerus, and the femur. Age and stature is determined by analyzing the development of the teeth, bone growth, cranial suture lines, and the length of specific bones, such as the femur. The race is determined by analyzing the skull for characteristics that are common among of different races. In a crime, skeletons and bones can also help determine injuries and the cause of death.


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