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FORENSICS

FORENSICS. Dante Chavez Trujillo. The discipline in which professionals use scientific means to analyze physical crime evidence Applies scientific method of discovery to legal issues Forensic scientists collect, preserve, and analyze scientific evidence during the course of an investigation.

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FORENSICS

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  1. FORENSICS Dante Chavez Trujillo

  2. The discipline in which professionals use scientific means to analyze physical crime evidence • Applies scientific method of discovery to legal issues • Forensic scientists collect, preserve, and analyze scientific evidence during the course of an investigation

  3. Fingerprinting – one of the first applications • Used by the ancient Chinese to identify business documents • First crime lab established in France in 1910 • First American crime lab establish in Los Angeles in 1924 • FBI did not have their own forensic crime laboratory until 1932 • By the end of the 20th century, scientists had many high-tech tools for analyzing evidence at their disposal

  4. UV spectrophotometry, Gas Chromatography, Mass spectrometry, solvent tests, various chemicals • Forensic Drug Testing • Paint Analysis • Arson Investigations • Gunshot Residue • Fibers • Fingerprints • Body fluids

  5. Also known as DNA profiling or DNA fingerprinting • First developed in 1984 by Sir Alec Jeffreys • Most commonly associated with forensic science • Analyzes DNA sequences to recognize patterns and comparison points that allows one set of DNA to be compared to another after a sample has been obtained

  6. RFLP analysis • Polymerase Chain Reaction (PCR) analysis • STR analysis • DNA family relationship analysis • Y-chromosome analysis • Mitochondrial analysis

  7. Restriction Fragment Length Polymorphism • One of the first methods used for DNA profiling • DNA collected and cut into small pieces using restriction enzymes • Different sizes of DNA fragments are generated and separated through the use of gel electrophoresis • Southern Blot • Requires large amounts of non-degraded sample DNA • Difficult to discern individual alleles

  8. Polymerase Chain Reaction • Made huge strides in the ability to recover information from very small or degraded DNA samples

  9. Short Tandem Repeat • One of the most useful methods in molecular biology used to compare specific loci on DNA from two or more samples • A short tandem repeat is a microsatellite consisting of two to thirteen nucleotides repeated hundreds of times in a row on a DNA strand • Nuclear DNA extracted > Amplification by PCR > Amount of repeats of STR sequence determined with gel • Different from RFLP – no restriction enzymes • Chances of two people having the exact same 13 STR regions virtually impossible

  10. Liquid or dry blood • Saliva • Hard tissues • Bone, teeth • Hair follicles • Various other biological secretions

  11. DNA efficiently recovered and extracted from the biological sample • Harvested on EDTA • Retains original shape and size of cells • PCR used to determine quantity of DNA and amplification • Detection and analyzation of amplified products • Interpretation

  12. DNA evidence difficult to prevent • Greater certainty than standard fingerprinting • Collected evidence can be stored long-term in databases • No specific sample size needed– can be amplified • 99.9% accurate

  13. An imperfect science – errors still happen • Relies on human accuracy • Technologists • Incorrect processing/handling techniques • Unreliable result interpretation • Not as easy and quick as TV makes it out to be • Wrongful conviction

  14. Wrongfully convicted of rape when his DNA was found on a genital swab • DNA was a perfect match and was the only evidence used to convict him • Scott claimed that he was more than 200 miles away on the night of the incident • Spent 5 months in custody until a technician from the crime lab came forward • Technician admitted to reusing a plastic plate that contained a sample of Scott’s saliva from an unrelated case • Case changed views on using DNA evidence as only type of proof

  15. Female serial killer linked to 40 crimes, “Woman without a face” • 6 out of the 40 crimes were murders • DNA from one individual found at every crime scene pointing to the same perpetrator • Evidence inconclusive • Never captured on a security camera and described as looking like a man by witnesses • March of 2009 case was closed • Investigators came to the conclusion that the Phantom did not exist and recovered DNA had been a result of contamination of the cotton swabs being used

  16. “The DNA on a weapon might come from the person who actually touched the object or the person who shook hands with the person who touched the object” • Christopher Philips, forensic geneticist • Study completed in 2015 to test this theory • Subjects were asked to shake hands with a partner for two minutes and then handle the same knife between the two • DNA was found on 85% of the knives handled • 20% of the cases showed more DNA present from the secondary source

  17. Show paternity or other familial relationships • Identify endangered/protected species • Prosecution of poachers • Detect bacteria polluting air, soil, water, and food • Match organ donors with organ receivers

  18. Gasiorowski-Denis, Elizabeth. “The Mystery of the Phantom of Heilbronn.” ISO, 6 July 2016, www.iso.org/news/2016/07/Ref2094.html. • “THE BEST REVIEW OF STR'S (SHORT TANDEM REPEAT) MUTATION | APPLIED TO THE FORENSIC.” YouTube, 23 Sept. 2015, youtu.be/9bEAJYnVVBA. • “Application of Next-Generation Sequencing Technology in Forensic Science.” Genomics, Proteomics & Bioinformatics, Elsevier, 14 Oct. 2014, www.sciencedirect.com/science/article/pii/S1672022914001053. • Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature News, Nature Publishing Group, 1 Oct. 2004, www.nature.com/articles/nrg1455. • Jamieson, Allan, and Scott Bader. “A Guide to Forensic DNA Profiling.” Wiley.com, 8 Mar. 2016, www.wiley.com/en-us/A+Guide+to+Forensic+DNA+Profiling-p-x000673241. • Murnaghan, Ian. “STR Analysis - Short Tandem Repeat.” STR Analysis - Short Tandem Repeat, 2018, www.exploredna.co.uk/str-analysis.html. • Jack Doyle for the Daily Mail. “Adam Scott: Innocent Man Spent FIVE MONTHS in Prison after Forensics Mix-up Meant He Was Falsely Accused of Rape.” Daily Mail Online, Associated Newspapers, 1 Oct. 2012, www.dailymail.co.uk/news/article-2211365/Adam-Scott-Innocent-man-spent-FIVE-MONTHS-prison-forensics-mix-meant-falsely-accused-rape.html. • “DNA Profiling.” Wikipedia, Wikimedia Foundation, 28 Oct. 2018, en.wikipedia.org/wiki/DNA_profiling#DNA_profiling_process. • Corazon, Dulce, and W. Everett. “What Is an EDTA Anticoagulant?” WiseGEEK, Conjecture Corporation, 20 Oct. 2018, www.wisegeek.com/what-is-an-edta-anticoagulant.htm. • Dumache, Raluca, et al. “Molecular Genetics and Its Applications in Forensic Sciences.” IntechOpen, IntechOpen, 7 Sept. 2016, www.intechopen.com/books/forensic-analysis-from-death-to-justice/molecular-genetics-and-its-applications-in-forensic-sciences. • Watson, Stephanie. “How Forensic Lab Techniques Work.” HowStuffWorks Science, HowStuffWorks, 8 Mar. 2018, science.howstuffworks.com/forensic-lab-technique4.htm. • Roos, Dave. “Why DNA Evidence Can Be Unreliable.” HowStuffWorks Science, HowStuffWorks, 15 Feb. 2018, science.howstuffworks.com/why-dna-evidence-can-be-unreliable.htm.

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