Forensic Science: Final Exam Review – Quick Curriculum Overview
· There are some sections where there is a little more information than we covered in class. It can’t hurt to review some of that, so I included it in this basic overview.
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:
o Testable
o Peer-Reviewed
o 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.
o Right to remain silent
o Anything you say can and will be used against you
o Right to an attorney
o If you cannot afford an attorney, one will be appointed to you
o 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:
o Secure/Isolate the scene
o Safety of victims
o Witnesses/statements
o Safety precautions
· Crime Scene Investigator Responsibilities:
o Documentation: pictures, sketches, notes
o Search Method
o Collection/Packaging of evidence
o 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
o Photographs
· As many as possible!!
· Overall views, Medium views, Close-up views
o Sketches
· Floor plan (“Bird’s Eye View)
· Triangulation Measurements (for Reconstruction purposes)
o Notes
· Observations using ALL of your senses (except taste!!)
· Conduct a systematic Search
o Spiral
· Outdoors, wooded area
o Quadrant/Zone
· Car/Vehicle
o Line/Strip
· Open Field
o Grid
· Indoor room/warehouse
· Collect, package, and label evidence properly!
o Biological evidence
§ Must be dried COMPLETELY and then packaged in a breathable bag or envelope.
o Trace evidence
§ Tape-lifted, then packaged in breathable bag or envelope
o Arson and explosive evidence
§ Contained in an air-tight canister (metal/plastic) IMMEDIATELY!
· Don’t forget to collect CONTROL SAMPLES!!
o sexual assault cases
· victim(s), suspect(s), sexual partner(s)
o homicides
· victim(s), suspect(s), others who have been in contact with CS
o hit-and-run accidents
· glass, paint, plastic, tire prints from suspect’s car
o 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
o General Crimes (burglary, larceny, etc…)
· VICAP: Violent Criminal Apprehension Program
o Sexual assault and homicides (serial crimes)
· AFIS: Automated Fingerprint Identification System
o Fingerprints
· CODIS: Combined DNA Identification System
o DNA
· GRCF: General Rifling Characteristics File
o Firearms
· IBIS: Integrated Ballistics Identification System
o Bulletproof: bullet analysis
o Brass Catcher: cartridge casing analysis
Physical Evidence
· Individual Evidence:
o Evidence that can be linked to ONE (1) individual source (i.e. person, animal, thing,…)
· Class Evidence:
o Evidence that can be linked to a group of sources (i.e. persons, animals, things,…)
· Biological Evidence:
o Physical evidence that IS/WAS/WAS FROM a living thing
· Trace Evidence:
o Extremely small or “invisible” physical evidence
· General Physical Evidence:
o A tangible item or substance that is used to prove any element/part of a crime
· Deductions from observations include…
o Color, approximate size, texture, smell, shape, ….
· Examinations/Forensic Analyses include…
o Mass, volume, density, thickness, temperature, microscopic, refractive index, chromatography, chemical analysis, ….
· Examples of Equipment….
o Balance, graduated cylinder, microscope, thermometer, laser, super glue fuming chamber, gas chromatograph/mass spectrometer, ….
Trace Evidence
· Locard’s Principle: “Every contact leaves a trace”
· Transfer of Trace Evidence
o Primary: Direct Transfer (from Source to suspect/victim/crime scene)
o Secondary: Indirect Transfer (from source to intermediate carrier to S/V/CS)
· Soil:
o Applications:
§ On Shoes
§ Tires
§ At the crime scene
§ On victim and/or suspect
o Analysis:
§ Color
§ Texture
§ Grain size
§ Density
· Hair: Appendage of the skin that grows out of the hair follicle (an organ)
o 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
o Types:
§ Natural: Animal or Plant source
§ Synthetic: “Man-Made”
o 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
o Identify a Question
o Gather Information and Resources (Research the Problem)
o Form a Hypothesis/Suggest a Solution
o Test the Hypothesis/Solution
o Analyze Data
o Interpret Data/Draw Conclusions
§ --Accept or Reject Hypothesis/Solution
o Re-test!!
o Report Results/Publish Results
· Why the Scientific Method?
o -To decrease bias
o -To provide a systematic, consistent procedure (PROTOCOL)
o -To validate results (3 or more trials resulting in the same/similar data)
· Fingerprints
o Who: All primates (including humans) have friction ridge patterns (fingerprints, palmprints, footprints)
o 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)
o Where: On every surface that a person touches
§ Three types:
· Latent (“invisible”)
· Patent/Visible
· Plastic (mold/cast of fingerprint)
o Why:
§ Two Rules that allow us to use fingerprints for identification:
· Unique to every individual *including identical twins
· Permanent for an individual’s lifetime
o *friction ridge patterns are formed in the 12th-16th week of fetal development
o *exceptions: scars and growth (size)
o When: More likely to leave a lasting print when fingers are warm and perspiring (oily)
Categorizing and Analyzing Fingerprints
· HENRY CLASSIFICATION!!!
· ACE-V
o Analysis: Qualitative and Quantitative Assessment
o Comparison: Agreement or Discrepancies between 2 fingerprints
o Evaluation: Consistent? Inconsistent? Inconclusive?
o Verification: A second independent analysis, comparison, and evaluation by another qualified examiner.
· Categorization
o Level 1: General ridge-flow
§ *Pattern
· Arch
· Loop
· Whorl
o Level 2: Formations and combinations
§ *Minutiae Points
o Level 3: Details within the formations
§ *dimensional attributes of a ridge
Biological Evidence
· Sources of Biological Material:
o Blood
o Semen**
o Saliva
o Urine
o Hair, Teeth, Bone, Tissue
· Types of Crimes Involving Body Fluids
o Sexual Assaults**
o Assaults
o Homicides**
o Burglaries
o Desecrations
· Process of Forensic Examination of Evidence
o Recognition
§ “What is important?” SCREENING/PRESUMPTIVE TESTS
o Identification
§ “What is it?” (class category) CONFIRMATORY TESTS
o 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
o Water, salts, inorganic ions, and organic compounds (urea & creatinine)
o Tests:
§ Azostix: detects Urease
· *false (+) for sweat, semen, vaginal secretion
§ Jaffe Test: detects Creatinine *also in sweat, bile, gastrointestinal fluids
o 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
o Tests:
§ Phadebas Test, Procion Red Amylopectin Test
§ Both tests detect α-Amylase (digestive enzyme) activity (β-Amylase is found in plants and bacteria)
§ Also found in: semen, vaginal secretion, serum, feces, perspiration, breast milk
· Semen: Seminal Fluid/Plasma + Spermatozoa
o 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 +α-naphthyl-phosphate
§ APase is a Very stable enzyme (tested after 20 years in dried stains)
· Positive result:: insoluble pink/purple colored product
o 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
o Individualization: DNA Tests
o 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
o 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:
o A complex mixture of cells, enzymes, proteins, and inorganic substances
o Components:
§ -Plasma = 55% of blood
· 90% water + 10% metabolites, waste, salts, ions, and proteins
§ -Solid portion:
· Erythrocytes = Red Blood Cells (RBC) (no DNA)
o Contain Hemoglobin which transports O2 from lungs to cells and CO2 from cells to lungs
· Leukocytes = White Blood Cells (WBC)
o Primary cells of the immune system—they produce antibodies
· Thrombocytes = Platelets (no nuclei)
o Start the clotting process by initiating the production of fibrin
o If clotted material is removed, left with yellow liquid = serum
o Blood Type:
Antigens are found on RBCs and Antibodies are produced by WBCs
Blood Type / Antigens on RBC / Antibodies in Serum / Donor For / Recipient ForA / 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??
o **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??
o Teichmann Crystal Test
§ forms brown visible crystals under the microscope
o Takayama Crystal Test
§ forms pink needle-shaped crystals under the microscope
o Precipitin Test
§ animal blood that has developed antibodies against human antigens when exposed to human blood will form a coagulated band at intersection
o Hematrace
§ immunological test—utilizes the antibody-antigen reaction
§ dye changes color when antibody-antigen coagulation occurs
· Individualization: DNA Tests
· Physical properties of Blood:
o -A viscous liquid that has the potential to dry!!
o -Consider all of the following when recreating a crime scene based on blood spatter: