Forensic Science Fundamentals

Week 1

• The scientific method follows a systematic approach, involving observation, question formulation, hypothesis development, experimentation, data collection, analysis, and conclusion
• Alphonse Bertillon developed anthropometry for personal identification
• Francis Galton studied fingerprints and developed a classification system of fingerprints
• Edmond Locard established Locard's Exchange Principle that every contact leaves a trace
• Hans Gross developed criminalistics
• Calvin Goddard used ballistics to match bullets to firearms
• Locard’s Exchange Principle means that contact with a crime scene transfers physical evidence: fibers, fingerprints, biological material suitable for forensic use
• Comprehensive crime labs feature specialized units
• Biology analyzes DNA, blood, and body fluids
• Firearms examines bullets, shell casings, and gunshot residue
• Document Examination analyzes handwriting, forgeries, and counterfeit documents
• Toxicology tests biological samples for drugs and poisons
• Latent Fingerprint identifies individuals using fingerprint analysis
• Blood samples are assigned to the Biology Unit
• Shoeprints are assigned to Impression Analysis
• Bullets and casings are assigned to Firearms Unit
• Handwriting evidence is assigned to Document Examination
• Forensic Entomology studies insects on decomposing bodies
• Forensic Odontology identifies remains using dental records
• Forensic Anthropology identifies remains using skeletal analysis
• Forensic science applies scientific methods to solve crimes
• Ballistics studies firearms and ammunition
• Serology studies body fluids
• Personal suspect descriptions are obtained via: eyewitness accounts, composite sketches, CCTV footage, and DNA profiling
• General features of a suspect include: height, weight, hair color and style, eye color, and facial features.
• Interviews are for information-gathering and are non-accusatory
• Interrogations are accusatory and aim to elicit confessions
• Common physical evidence at crime scenes includes biological (blood, hair, saliva), chemical (drugs, toxins), and impression (fingerprints, shoe prints)
• Identification determines what an object or substance is
• Individualization ties evidence to a specific person or source
• Individual characteristics are unique to a single source, like fingerprints or DNA
• Class characteristics are shared by multiple sources, for example fibers or paint
• Class evidence narrows the suspect pool at a crime scene
• The product rule calculates the probability of independent characteristics occurring together by multiplying individual probabilities
• Computerized databases of physical evidence include: AFIS (fingerprints), CODIS (DNA profiles), and NIBIN (firearm ballistics)

Week 2

• The first responding officer to secure the scene and provide medical aid
• The first responding officer starts a crime scene log, and identifies/ separates witnesses
• Recording a crime scene involves photography, sketching and detailed notes
• Crime scene sketches include: rough sketches (quick hand-drawn) and final sketches (detailed, to scale)
• Crime scene searches include: Grid search (large outdoor areas), Spiral search (confined spaces), and Strip search (open fields)
• Packaging evidence involves: Blood samples in paper envelopes, bullets in hard plastic containers, and fibers secured via tweezers into sealed bags
• Chain of custody refers to maintaining proper documentation to track the handling of evidence
• Maintaining health and safety standards at a crime scene requires: wearing gloves and masks, avoiding contamination, and proper disposal of biohazardous materials
• Human remains are analyzed via: DNA to identify victims, skeletal analysis to determine: age, sex, ancestry, and forensic entomology to estimate time of death

Week 3

• Skulls are used for determination of ancestry and sex
• Pelvises are the best indicator of biological sex
• Long bones are used for height estimation
• Measurement of all skeletal elements is done via: Femur length to estimate stature, and skull measurements to determine ancestry
• Polymerase Chain Reaction (PCR) amplifies DNA from small samples for forensic identification
• Short Tandem Repeat (STR) analysis compares repetitive DNA sequences at specific loci to establish an identity
• Nuclear DNA is inherited from both parents and unique to an individual
• Mitochondrial DNA is inherited from the mother and useful for degraded samples
• Bloodstained evidence is preserved for DNA analysis by: storing in a dry paper bag, refrigerating liquid samples, and avoiding contamination
• Calculating the occurrence probability of a DNA profile using demographic data uses population genetics to estimate the likelihood of a match

Week 4

• Toxicology is the study of drugs, poisons, and their effects on the human body
• Blood Alcohol Concentration (BAC) is the amount of alcohol in a person's bloodstream, concentration is measured in grams per 100 mL of blood
• Metabolism is the process by which the body breaks down substances like alcohol
• Agglutination is the clumping of cells or particles, commonly seen in blood typing
• In South Africa, the legal Blood Alcohol Concentration (BAC) limit is 0.05g per 100ml of blood
• For professional drivers in South Africa, the legal Blood Alcohol Concentration (BAC) limit is 0.02g per 100ml of blood
• Alcohol is absorbed into the bloodstream via the stomach/small intestine, transported throughout the body by blood, and the liver metabolizes about 90%. The remaining alcohol is excreted via urine, sweat, and breath
• Key parts of the human circulatory system include: heart, arteries, veins, and capillaries
• Alcohol is excreted in breath as it evaporates from blood in the lungs and is expelled through the alveoli (tiny air sacs) when a person breathes out
• Measuring alcohol involves: Infrared breathalyzer (measures infrared light absorbed by alcohol molecules) and fuel-cell breathalyzer (uses chemical reaction to generate electric current)
• Common field sobriety tests for alcohol impairment are: Horizontal Gaze Nystagmus (HGN), the Walk-and-Turn Test, and One-Leg Stand Test
• Laboratory procedures for measuring blood alcohol concentration include: Gas Chromatography and Enzyme-Based Blood Tests
• Preserving blood samples for alcohol content analysis involves: using preservatives (sodium fluoride) to prevent bacterial fermentation and storing at a low temperature to prevent alcohol evaporation
• Toxicologists detect/identify drugs, poisons, and alcohol in biological samples and provide expert testimony in court
• Isolation and Identification techniques for drugs and poisons include: Gas Chromatography-Mass Spectrometry (GC-MS) and Thin-Layer Chromatography (TLC)
• Active drugs in the bloodstream determine impairment
• Finding drugs in human tissues indicates recent usage
• Type A blood has A antigen, anti-B antibodies
• Type B blood has B antigen, anti-A antibodies
• Type AB blood has A and B antigens, no antibodies
• Type O has no antigens, both anti-A and anti-B antibodies
• Agglutination is caused by antibodies that attack foreign antigens resulting in clumping when mixing incompatible blood types

Week 5

• Blood samples are mixed with anti-A and anti-B serums for blood typing
• Clumping indicates if a corresponding antigen is present
• Tests to characterize a stain as blood: Kastle-Meyer Test, Luminol Test, and Hemastix Strips Test
• Identifying species and drugs relies on antigen-antibody reactions
• Double diffusion precipitin tests place antibodies and antigens in a gel to see if a visible precipitate forms
• Monoclonal antibodies are produced from a single immune cell, and is highly specific
• Polyclonal antibodies are Derived from multiple immune cells
• Acid Phosphatase tests are used to detect enzymes in semen
• Prostate-Specific Antigen (PSA) tests are done to confirm the presence of seminal fluid
• To preserve suspect blood and semen stains: dried semen-stained items will need to be stored in paper bags and kept in cold storage until tested
• Collect clothing and swabs from victim for a rape investigation
• Document injuries (bruises, scratches), and use Sexual Assault Evidence Collection Kits (SAECKS) for rape kit
• Smooth surfaces produce circular stains from bloodstains
• Rough surfaces create irregular bloodstains, that includes spines
• Angle of impact of bloodstains measured using stain length-to-width ratio
• Classifications of impact spatter include: low velocity (4 mm larger drops), medium velocity (1-4 mm drops) and high velocity (1 mm smaller drops)
• Convergence area is traced by tracing bloodstain direction back until lines intersect
• Origin areas are used to determine where blood came from in 3D space via angle of impact
• Passive bloodstains result from gravity (drops, pools)
• Transfer stains result from moving an object through blood (handprints, footprints)
• Projected bloodstains occur by applied force (arterial spray, impact spatter)
• Documenting bloodstain patterns can be done through: photography, sketching, and string method
• Rifling involves spiral grooves that are etched in a gun barrel
• Firearms are weapons that launch a projectile using gunpowder or another explosive
• Ballistics is the study of the motion, behavior, and effects of projectiles
• Gunshot residue (GSR) are tiny particles, containing lead, barium, and antimony, are expelled when a gun is fired
• Rifling are spiral grooves inside a barrel for bullet spin
• Shotguns fires multiple pellets (shot) or a single slug and include smooth bores
• Rifles fires a single bullet with accuracy via rifled grooves
• Handguns are short barreled firearms for one hand
• Bolt-action rifles require manual cycling of the bolt
• Semiautomatic rifles fires one shot per trigger pull
• Revolvers use a rotating cylinder
• Broach cutting makes gun barrels with cutting egdes
• Button rifling uses pressure to create the grooves in a barrel
• Hammer forging uses hammering around a mandrel to shape the rifling
• Electrochemical machining uses electrical currents
• Cut rifling involves a tool that creates one groove at a time
• Polygonal rifling create smoother grooveds in barrels
• Class characteristics can be common with a group (caliber, and amount of lands/ grooves)
• Individual characteristics are only be unique to one gun (striations, and firing pin marks)
• Test-fired bullets are used in microscopes to match rifling marks
• National Integrated Ballistic Information Network (NIBIN) helps link firearms by comparing casings markings
• The location of firearm wounds can determine the distance of firing due to the wound patterns
• Contact shots tend to leave soot with burning around the wound
• Distant shots tend to include no residue or burning, only a bullet hole
• Laboratory tests for residue of GSR may include: Modified Griess Test and Scanning Electron Microscopy (SEM)
• Obliterated serial numbers are recoverable due to the compressed metal underneath the nummber
• A crime scene firearm cannot be placed in plastic; must be labelled; keep bullets stored separately

Week 6

• Law is a set of rules established by authorities to regulate behavior and maintain order in society
• South African legal system is based on Roman-Dutch law and English common law
• Kinds of Law: Criminal (punishments), Civil (individual disputes), and Constitutional (govt v citizen disputes)
• South African courts have different jurisdictions: Constitutional Court ( constitutional issues), Supreme Court of Appeal (appeals in lower courts), and Magistrate’s Courts (criminal and civil cases)
• The procedure followed in the criminal justice system: investigation to arrest to court to sentencing to appeals(if applicable)
• Witnessees must testify and provide expert testimony(such as forensics)
• Prosecutors try and seek justice
• Objection formal protest in court room
• Hearsay is second hand information of events in the courtroom
• In hair follicle samples the medulla is the central core and will vary in appearance
• Cortex has pigments and is found in the follicle
• The cuticle has scales and protects from the outside and has shingles
• phases of growth are active, change , resting(anagen, catagen, telogen)
• animal and human hair will differ mostly in the hair's medulla
• animal hair includes a medulla that is thick and well defined
• hair comparison is judged via color thickness, pigment distribution, cuticle pattern
• Forensic hair samples must be handled carefully via forceps and sealed envelopes
• Hair follicle dna is important; mitochondrial dna can suggest the maternal lineage
• Hair cuticle = Scales overlap or look like shingles
• Primary fingerprint is: Arches, loops and whorls
• Secondary fingerprint is: Minutiae; ridge details
• Fingerprints do not change and are permanent in the womb through life
• Visible finger prints in ink or soft clay/wax
• Invisible =Latent
• Automated Fingerprinting is done in system-databases AFIS
• Latent nonporous prints =Fingerprint powders
• Porous = ninhydrin/ iodine
• preserve hair via rolling prints & ink and scanners

Week 7

• Identifying eruption patterns can help estimate a person age.
• Understanding forensic dentistry important aspects include: overbite and underbite. cross bite
• Teeth resist decay and are important to help with identification
• Bite analysis important in matching suspects with samples