Forensic Science: Final Exam Review 2013

Forensic Science: Final Exam Review Unit 1: Crime Scene Investigation Forensic Science: The study and application of science to matters of the law Physical Evidence: An object or substance that is used to prove elements of a crime Testimonial Evidence: A verbal account of events or details of a crime given by a witness and/or expert Circumstantial Evidence: Evidence that is collected (either physical or testimonial) that is used INDIRECTLY to prove elements of a crime. This type of evidence DOES NOT PROVE GUILT! Expert Witness: A person who is specially trained and certified in an area that allows him or her to testify in court (i.e. Medical Examiner, Blood Spatter Expert) The Frye Standard: Expert opinion based on a scientific technique is admissible only where the technique is generally accepted as reliable in the relevant scientific community (The “General Acceptance Rule”) The Daubert Standard: Scientific technique admissible in court if it is: Testable Peer-Reviewed Rate of Error must be given (exception to rule #3: fingerprints) Miranda Rights: Rights that are guaranteed by the Constitution of the United States of America. An individual MUST be read his or her rights prior to being arrested. Right to remain silent Anything you say can and will be used against you Right to an attorney If you cannot afford an attorney, one will be appointed to you If you answer questions without an attorney, you have the right to stop Probable Cause: The standard by which an officer has the grounds to obtain a warrant to search and/or arrest an individual Individual Characteristics: Features or details that link a piece of evidence to one single source (i.e. DNA, Fingerprints, Serial Numbers) Class Characteristics: Features or details that link a piece of evidence to a group of sources (i.e. Tire Tracks, Shoe Prints) Crime Scene Reconstruction: To recreate the crime scene in order to determine the chain of events that led up to a crime Motive: The reason a crime was committed Means: The weapon, tool, or strength used to commit the crime Opportunity: The window of time during which the crime was committed Chain-of-Custody: A written record of all people who have had possession of an item of evidence (to ensure its validity and avoid contamination) Control Sample: A known evidentiary sample that is collected in order to compare unknown evidence samples collected from the crime scene, victim, and/or suspect. (i.e. A suspect’s fingerprints are collected as a control sample to compare it to the fingerprints found on a knife near the victim) Crime scene protocols: First Responder Responsibilities: Secure/Isolate the scene Safety of victims Witnesses/statements Safety precautions Crime Scene Investigator Responsibilities: Documentation: pictures, sketches, notes Search Method Collection/Packaging of evidence Deliver evidence to the lab (chain-of-custody) Order of protocol: Secure and isolate the crime scene Help anyone who is injured Process the crime scene Documentation Photographs As many as possible!! Overall views, Medium views, Close-up views Sketches Floor plan (“Bird’s Eye View) Triangulation Measurements (for Reconstruction purposes) Notes Observations using ALL of your senses (except taste!!) Conduct a systematic Search Spiral Outdoors, wooded area Quadrant/Zone Car/Vehicle Line/Strip Open Field Grid Indoor room/warehouse Collect, package, and label evidence properly! Biological evidence Must be dried COMPLETELY and then packaged in a breathable bag or envelope. Trace evidence Tape-lifted, then packaged in breathable bag or envelope Arson and explosive evidence Contained in an air-tight canister (metal/plastic) IMMEDIATELY! Don’t forget to collect CONTROL SAMPLES!! sexual assault cases victim(s), suspect(s), sexual partner(s) homicides victim(s), suspect(s), others who have been in contact with CS hit-and-run accidents glass, paint, plastic, tire prints from suspect’s car braking-and-entering window glass, paint, tool marks from items within suspect’s possession Legal Considerations: Must have a warrant to arrest and/or search UNLESS: Emergency Circumstances Injury? Danger? Life-threatening circumstances? Prevent loss or destruction of evidence “flushing drugs down toilet?”—VERY difficult to prove!! Search of person or property in connected to a lawful arrest DUI—once someone is placed under arrest they, their vehicle, and anyone in the vehicle may be searched Search made with consent of person(s) involved Investigators are invited into someone’s home, office, etc… Criminal Databases NCIC: National Crime Information Center General Crimes (burglary, larceny, etc…) VICAP: Violent Criminal Apprehension Program Sexual assault and homicides (serial crimes) AFIS: Automated Fingerprint Identification System Fingerprints CODIS: Combined DNA Identification System DNA GRCF: General Rifling Characteristics File Firearms IBIS: Integrated Ballistics Identification System Bulletproof: bullet analysis Brass Catcher: cartridge casing analysis Unit 2: Physical Evidence Individual Evidence: Evidence that can be linked to ONE (1) individual source (i.e. person, animal, thing,…) Class Evidence: Evidence that can be linked to a group of sources (i.e. persons, animals, things,…) Biological Evidence: Physical evidence that IS/WAS/WAS FROM a living thing Trace Evidence: Extremely small or “invisible” physical evidence General Physical Evidence: A tangible item or substance that is used to prove any element/part of a crime Deductions from observations include… Color, approximate size, texture, smell, shape, …. Examinations/Forensic Analyses include… Mass, volume, density, thickness, temperature, microscopic, refractive index, chromatography, chemical analysis, …. Examples of Equipment…. Balance, graduated cylinder, microscope, thermometer, laser, super glue fuming chamber, gas chromatograph/mass spectrometer, …. Unit 3: Trace Evidence Locard’s Principle: “Every contact leaves a trace” Transfer of Trace Evidence Primary: Direct Transfer (from Source to suspect/victim/crime scene) Secondary: Indirect Transfer (from source to intermediate carrier to S/V/CS) Soil: Applications: On Shoes Tires At the crime scene On victim and/or suspect Analysis: Color Texture Grain size Density Hair: Appendage of the skin that grows out of the hair follicle (an organ) Parts of Hair: Bulb Root Cuticle Cortex Medulla Fibers: The smallest unit of a textile material that has a length many times greater than its diameter Types: Natural: Animal or Plant source Synthetic: “Man-Made” Analysis: Fiber Structure Comparison Microscope Scanning Electron Microscope (SEM) Cross-section of fiber (triangular, star-shaped) Fiber Colors Microspectrophotometer spectral patterns and Becke lines crystallinity? Thin Layer Chromatography: separate components (colors) in dyes Fingerprints The Scientific Method Identify a Question Gather Information and Resources (Research the Problem) Form a Hypothesis/Suggest a Solution Test the Hypothesis/Solution Analyze Data Interpret Data/Draw Conclusions --Accept or Reject Hypothesis/Solution Re-test!! Report Results/Publish Results Why the Scientific Method? -To decrease bias -To provide a systematic, consistent procedure (PROTOCOL) -To validate results (3 or more trials resulting in the same/similar data) Fingerprints Who: All primates (including humans) have friction ridge patterns (fingerprints, palmprints, footprints) What: Raised ridges and furrows that are designed to help grasp items At the top of the ridges are sweat pores that release: 99% H2O 1% oils, fatty acids, esters, salts, urea, amino acids Total volume of 1 adult fingerprint = a few microliters (µL) Where: On every surface that a person touches Three types: Latent (“invisible”) Patent/Visible Plastic (mold/cast of fingerprint) Why: Two Rules that allow us to use fingerprints for identification: Unique to every individual *including identical twins Permanent for an individual’s lifetime *friction ridge patterns are formed in the 12th-16th week of fetal development *exceptions: scars and growth (size) When: More likely to leave a lasting print when fingers are warm and perspiring (oily) Categorizing and Analyzing Fingerprints HENRY CLASSIFICATION!!! ACE-V Analysis: Qualitative and Quantitative Assessment Comparison: Agreement or Discrepancies between 2 fingerprints Evaluation: Consistent? Inconsistent? Inconclusive? Verification: A second independent analysis, comparison, and evaluation by another qualified examiner. Categorization Level 1: General ridge-flow *Pattern Arch Loop Whorl Level 2: Formations and combinations *Minutiae Points Level 3: Details within the formations *dimensional attributes of a ridge Unit 4: Biological Evidence Sources of Biological Material: Blood Semen** Saliva Urine Hair, Teeth, Bone, Tissue Types of Crimes Involving Body Fluids Sexual Assaults** Assaults Homicides** Burglaries Desecrations Process of Forensic Examination of Evidence Recognition “What is important?” SCREENING/PRESUMPTIVE TESTS Identification “What is it?” (class category) CONFIRMATORY TESTS Individualization “Who or What did it come from?” (uniqueness) Serology: The study of bodily fluids using specific antigen and serum antibody reactions Secretors: 80% of population have blood antigens (A & B) in other bodily fluids Types of Bodily Fluids: Urine, Saliva, Semen, Blood Urine: Waste secreted by the Kidneys Water, salts, inorganic ions, and organic compounds (urea & creatinine) Tests: Azostix: detects Urease *false (+) for sweat, semen, vaginal secretion Jaffe Test: detects Creatinine *also in sweat, bile, gastrointestinal fluids AT LEAST 5-20 mL necessary for possible DNA testing Saliva: 99.5% water, and 0.5% mixture of mucous, inorganic ions, proteins, epithelial cells Tests: Phadebas Test, Procion Red Amylopectin Test Both tests detect ?-Amylase (digestive enzyme) activity (?-Amylase is found in plants and bacteria) Also found in: semen, vaginal secretion, serum, feces, perspiration, breast milk Semen: Seminal Fluid/Plasma + Spermatozoa Screening Tests: UV/Alternate Light Source Visualization Fluorescence properties of 4-methyl umbelliferyl phosphate (MUP) with APase Seminal Acid Phosphatase (APase) Test: Fast Blue B dye +?-naphthyl-phosphate APase is a Very stable enzyme (tested after 20 years in dried stains) Positive result:: insoluble pink/purple colored product Confirmatory Tests: “Christmas Tree” Staining (using microscope) Spermatozoa is stained red (head), green (middle), and yellow (tail) Abacus One Step ABA card p30 Test Prostate Specific Antigen (PSA or P30) = human seminal fluid protein that is secreted by prostate gland Positive result: dye-colored insoluble band on card Individualization: DNA Tests Sexual Assault Crimes: Statistics and Information 78 rapes/hr in USA and 9/10 victims are female 80% victims are under 30 years old (high risk: 12-34 years old) 76% of female victims knew their assailant What to collect? -Clothing -Bedding -Fingernail/toenail scrapings, -Combings (head and pubic hair) -Blood: within 12-24 hours after assault -Urine: within 36-72 hours after assault -Semen: within 24-48 hours after assault **4 swabs from each orifice DON’T FORGET CONTROLS!! Blood: A complex mixture of cells, enzymes, proteins, and inorganic substances Components: -Plasma = 55% of blood 90% water + 10% metabolites, waste, salts, ions, and proteins -Solid portion: Erythrocytes = Red Blood Cells (RBC) (no DNA) Contain Hemoglobin which transports O2 from lungs to cells and CO2 from cells to lungs Leukocytes = White Blood Cells (WBC) Primary cells of the immune system—they produce antibodies Thrombocytes = Platelets (no nuclei) Start the clotting process by initiating the production of fibrin If clotted material is removed, left with yellow liquid = serum Blood Type: Antigens are found on RBCs and Antibodies are produced by WBCs Blood Type Antigens on RBC Antibodies in Serum Donor For Recipient For A A B A, AB A, O B B A B, AB B, O AB A and B None AB All O None A and B All O Rh + D ---- Rh - ---- D Universal Donor: O- Universal Acceptor: AB+ *Blood has 100 sub types to further identify victim or perpetrator Screening Tests: IS IT BLOOD?? **All use an oxidizable colorless chemical + an oxidizing agent that is catalyzed by “heme” (hemoglobin) to produce a visible product (color or light) Luminol = product fluoresces when in presence of heme Kastle-Meyer test = phenolphthalein (PHTH) that turns bright pink Hemastix (Benzidine test) Ortho-tolidine test Leucomalachte green test Confirmatory Tests: IS IT HUMAN BLOOD?? Teichmann Crystal Test forms brown visible crystals under the microscope Takayama Crystal Test forms pink needle-shaped crystals under the microscope Precipitin Test animal blood that has developed antibodies against human antigens when exposed to human blood will form a coagulated band at intersection Hematrace immunological test—utilizes the antibody-antigen reaction dye changes color when antibody-antigen coagulation occurs Individualization: DNA Tests Physical properties of Blood: -A viscous liquid that has the potential to dry!! -Consider all of the following when recreating a crime scene based on blood spatter: surface texture direction the blood traveled degree of circular distortion (angle of impact): sin-1(width/length) stain convergence lines (point of origin = where all droplets originated from) DNA Uses for DNA/Human Identity Testing: Forensic Criminal Cases CODIS = Combined DNA Index System What type of forensic case is DNA mostly used for? Rape/Sexual Assault (more than 2 out of 3 cases) Paternity Testing Historical Investigations Missing Persons Investigations Mass Disasters Military DNA (“dog tag”) What part of a DNA is used for forensic purposes? NON-CODING DNA = Spacer DNA = “junk DNA” ? 0.1% (3 million bases) is unique to an individual person ? 99.9% same genome fore every person DNA = Deoxyribonucleic Acid “The Blueprint for Life” Structure of DNA: CELL ? NUCLEUS ? CHROMOSOME ? GENE ? BASE PAIR Double Helix structure composed of base pairs Base Pairs: Adenine-Thymine, Cytosine-Guanine Genes are what “code” for bodily structures and functions Mutations are changes within the genes from one generation to the next Steps for DNA Processing: 1. DNA Extraction 2. DNA Quantification 3. PCR Amplification 4. Analysis Two Methods of Processing DNA: 1. Restriction Fragment Length Polymorphism (RFLP) 2. Polymerase Chain Reaction (PCR) + Short Tandem Repeat (STR) Restriction Fragment Length Polymorphism (RFLP): Larger sample size necessary (dime-quarter sized drop/stain) Uses gel electrophoresis Restriction enzymes (“chemical scissors”) cut the DNA at specific recognition sites. This “cutting” process generates different sized pieces of DNA. The DNA fragments are placed in an electrophoresis gel and a charge is applied (+ at one end and - at the other end). The different sized fragments migrate towards the + end of the gel. The smaller pieces move the fastest and farthest. The different sized fragments produce bands along the gel. To visualize the bands, x-ray film is used. PCR + Short tandem repeats (STR) PCR: makes many copies of a segment of DNA (DNA amplification) Short Tandem Repeats (STR) How it works: Restriction enzymes recognize a specific repeating pattern and cuts the DNA fragment at the beginning and end. This generates different sized fragments. Gel electrophoresis or capillary electrophoresis is then run to separate the different fragments. Mitochondrial DNA (mtDNA) Analysis: mtDNA comes from Mother If we cannot obtain nuclear DNA (nDNA) it can be used for identification purposes Unit 5: Forensic Toxicology Toxicology: Endogenous Substance: Naturally Occurring in the Body. Exogenous Substance: Foreign substance (drug or toxin) in the body Toxin: Any material exerting a life-threatening effect upon a living organism. A toxic response requires: Exposure Dose Mechanism (how it interferes with bodily functions) Toxicology: The science of adverse effects of chemicals on living organisms. Toxic effect depends on Depend on: Age Weight Health Dose Toxic effect can be: Hemolytic: Attacking the circulatory system and muscle tissue Neurotoxic: Attacking the central nervous system (CNS) causes heart failure and breathing difficulties Receptor: A large molecule on the cell’s surface where neurotransmitters induce their normal effects. Agonist: The drug or poison mimics the action of the transmitter. Antagonist: The drug or poison binds to a receptor and blocks the transmitter. Routes of entry: Orally Tablets, capsules, liquids Rectally Suppositories Intravenously Injected in liquid form through a needle Inhaled through lungs Gases, vapors, or particles Absorption through skin Patches on skin Absorption through mucous membranes Snorting, sniffing, or under the tongue In the body: Absorption: The drug/toxin enters the body Distribution: The drug/toxin moves throughout the body Metabolism: The breakdown or digestion of the drug/toxin into smaller molecules or products Elimination: The removal or excretion of the metabolites ED50: The dose size that produces the desired effects of a drug/toxin in 50% of a population/test group LD50: The dose size that produces a lethal effect of a drug/toxin in 50% of a population/test group Therapeutic Index = LD50/ED50 toxic dose/therapeutic dose Poisons: Venom is composed of many different Proteins Tissue damage (necrosis) caused by: Metalloproteinases Muscle damage (necrosis) caused by: Myotoxin-a (MA) Coagulopathy (Defibrination: loss of fibrin): Fibrin-like enzyme Platelet Deficiency caused by: Phospholipases Cardiotoxins: Myocardial depressant protein Neurotoxins: Causes weakness and paralysis Hemolysin: Loss of hemoglobin from RBCs Lecithinase A Hemolytic: Targets Circulatory/Muscle Systems Neurotoxic: Targets CNS/Heart 12 Heavy Metals have the potential to be toxic at high levels High molecular weight Interfere with enzyme systems and the metabolism of the body Drugs: Depressants Alcohol, barbiturates, tranquilizers, inhalants, GHB, rohypnol Hallucinogens THC, LSD, PCP, Mescaline, Psilocybin, Ketamine Stimulants Cocaine, Amphetamines, Meth, Caffeine Narcotics (Opiates, Opioids) Morphine, Codeine, Heroin, Darvon, Methadone Steroids Corticosteroids, Anabolic Steroids Antidepressants Tricyclics, MAOI’s, SSRI’s Unit 6: Ballistics Unit 7: Serial Killers