Forensics

Week 8 Trace evidence is often the key to an investigation and may be your only evidence. It is critical to understand what trace evidence can do for the investigator.
What is the composition of vehicle paint layers?
What is the best way to examine paint chips and how are they evaluated?
How is soil collected and preserved at a crime scene.
What standard/reference samples need to be collected?
How is soil examined?
What does the scientist look for?

Trace evidence is anything left behind at a scene of a crime that can potentially link a suspect and a victim to a mutual location. Examples of trace evidence are hair, fibers, gunshot residue, soil and pollen. Any of these items can be transferred between two or more people, objects or environment with little contact, so during a crime its easily done (Trace, 2012).
Analysis of trace material begins with a visual examination of the evidence while
Macrophotography is taken to ensure approximate pictures are taken or all aspects of the scene and surrounding evidence. It’s then followed by micro-analysis, a process that allows scientists to investigate the evidence at a microscopic level to analyze substances like chemical residues
(Trace, 2012). Other equipment used when analyzing trace materials are electron microscopes- used for the analysis of gunshot residue, spectrometry, spectroscopy and chromatographs- used to analyze small explosives, volatile hydro-carbonic chemicals and vehicular paint samples (Corbis, 2006).
To analyze vehicle paint, scientist must breakdown its complex mixture of color. Paint is formed of pigments, modifiers, extenders, and binders. Pigment is what gives paint its color, modifiers control the gloss, extenders add bulk and covering capacity, while binders stabilize the mixture and form the film when spread. When investigators have to analyze a paint chip they use a technique called pyrolysis gas chromatography to determine the paints composition. This involves heating a sample until it becomes a vapor to separate its components to create a chemical fingerprint that can be compared to reference samples. Once complete, it can help narrow down the make, model, and sometimes the year of a car so I its easier for investigators to catch the perpetrator (Corbis, 2006).

REFERENCE
Trace Evidence (2012); National Institute of Justice. Retrieved December 26, 2012 from http://www.nij.gov/topics/forensics/evidence/trace/trace.htm Corbis, S (2006); Gas chromatograph-mass spectrometer. Retrieved December 26, 2012

from http://www.enotes.com/paint-analysis-reference/paint-analysis

Week 10
DNA is the evidence everyone wants to see in an investigation. It is extremely fragile and even has its limitations.
Identify and explain items that should be collected from the victim and the suspected perpetrator of a sexual assault.
What is CODIS?
What samples are included in the CODIS database?
What is PCR/STR analysis and how is it used?
What is mtDNA?
Where does mtDNA come from?
How can it help the investigation?

Deoxyribonucleic acid or DNA, is the building block of the human body. Every cell contains in the body contains that person’s DNA, their blood, skin, hair, semen, saliva and bone.
And since no two people, with the exception of identical twins, share the same DNA- investigators use this as a powerful tool in crime scene analysis (Arnold, 2012).
DNA evidence collected from a crime scene can link a suspect to a crime or victim through a biological match. During asexual crime, evidence like hair, skin, semen and/or blood can be left on the victim, suspect or crime scene and used by investigators to make theories and links. Collected DNA is compared with referenced samples and ran through the FBI’s Combined
DNA Index System (CODIS) to link suspects anywhere in the United States to each other (Arnold, 2012). Polymerase Chain Reaction or PCR is the most common form of DNA analysis. It allows investigators to analyze a limited quality of collected evidence to generate a general DNA profile that matches . Mitochondrial DNA or mtDNA is the specifically inherited maternal found on mitochondria cells of the hair, nails, bones, et cetera. The Mitochondrial DNA Unit uses collected evidence to from crime scenes to put together possible sequences in family history or to link individuals within a particular family (Frank, 2011).
REFERENCE
Arnold, Matthew W. Laboratory Services- Combined DNA Index System (2012); Retrieved December 26, 2012 from: http://www.fbi.gov/about-us/lab/biometric-analysis/codis
Frank, Terry M. Biometric Analysis- Mitochondrial DNA (2011); Retrieved December 26, 2012 from: http://www.fbi.gov/about-us/lab/biometric-analysis/mtdna