Chem

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Basic Terms
• forensic (adj)
1. pertaining to, connected with, or used in court of law or public discussion and debate 2. adapted or suited to argumentation; rhetorical

Forensic Chemistry

• Forensic science (n.)
– the application of science to criminal and civil laws. – Emphasizes the application of science to criminal and civil laws that are enforced by police agencies in a criminal justice system. • Adversarial system

– owes its origins to individuals such as Bertillon, Galton, Lattes, Goddard, Osborn, and Locard, who developed the principles and techniques needed to identify or compare physical evidence.

Basic Terms
• criminalistics (n)
– the science dealing with the detection of crime and the apprehension of criminals – derived from the German “Kriminalistic” • coined in early 1900’s to attempt to better describe the emerging discipline of “police science”.

• Forensic CHEMISTRY
– Applied analytical chemistry
• Qualitative, quantitative AND Comparative
– LOTS OF STATS AND PROOF!

• Identify, classify and qualify

What makes a Science Forensic?
• An experimental result has no standing until it is disseminated to the rest of the scientific community – peer-reviewed journal – allows the experiment to be repeated & the results reproduced

What makes a Science Forensic?
• A product of the scientific community not individuals • Review of forensic experiments – another analyst in the laboratory – an analyst assisting opposing counsel

• Review necessary
– to catch any clerical errors – establish that conclusions are supported by data

• Data is not considered valid until reproduced by an independent source

The Null Hypothesis
• The stated idea is untrue • Often assumed in forensic science – “bullet didn’t come from this gun”

The Scientific Method
1.State an hypothesis (What is the question?)
– “I think that this bullet came from that gun” – we often set out to prove the null hypothesis – formulating a hypothesis is not bias although bias can cause the wrong question to be asked • “How did O.J. kill Nicole Brown Simpson & Ron Goldman?” (wrong) • “Did O.J. Simpson kill Nicole Brown Simpson & Ron Goldman?” (appropriate)

• Failure to disprove the null hypothesis
– provides evidence that the bullet did pass through the gun

The Scientific Method
2. Design an experiment to test the hypothesis
– compare the bullet microscopically with other test bullets known to have been fired from the gun – test bullets are the reference samples to which the crime scene bullet will be compared

The Scientific Method
3. Make observations and record data
– photograph the questioned & reference bullets through the microscope – record the number of features in common • how many • where they are located

– a general impression that they were the same or that they were not the same is not acceptable

Standards and Controls
• Experiments include standards & controls
– controls
• samples for which the results are known • show that the experimental system is working properly – microscope must be calibrated so the two bullets fired from the same gun can be matched up

Standards and Controls
• Normally in research, only one variable at a time is changed – allows the establishment of cause & effect
• when temp is varied (the variable), water assumes different forms (the outcome)

– standards
• devices with which the results of an experiment can be measured

• In forensic science, the original conditions that produced the sample are unknown – many conditions may have acted to produce the sample as it was found

Standards and Controls
• Forensic analysis is an uncontrolled experiment • You can establish that lab tests have worked properly • Some aspects of the sample will remain unknown

The Scientific Method
4. Analyze and interpret the data
– once data is collected, it must be analyzed – bullet comparison • analysis
– scrutinize the marks to determine if any differences between...
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