Forensic Science: Scientific Method

Module 1: Introduction to Scientific Method

• The scientific method is a way to find answers to a hypothesis, applicable in any type of research.
• In forensic science, an example hypothesis could be "Bob committed the crime".
• Observational research includes interviewing witnesses and staking out a location.
• Data collection starts at the crime scene, where evidence is gathered and moved to the lab for analysis.
• This data is reported, and new hypotheses are tested, unless the data confirms the initial hypothesis.
• The legal process starts towards a trial when data supports the hypothesis.
• Research forms include observational, experimental, case study, and natural study research.
• Scientific research in forensics necessitates user testing of manufacturer's new methods/tech.
• Evidence testing and reporting carries serious legal penalties.
• Benefits, limitations, and conditions for method use, along with training needs, all require determination.
• Research in labs, private institutions, and academia must be presented, published, peer-reviewed, and legally admissible in court.
• Forensic community acceptance helps determine if a method is valid and true.
• Developmental validation uncovers the benefits/limitations of methods/equipment via manufacturer research.
• Internal validation requires scientists/users to determine the method's effectiveness within their hands and lab workflow.
• Validation studies in court either support or deny crime-solving tech and whether equipment results should be used.
• Forensic lab positions focusing on these concepts include Research and Validation Coordinator, Technical Leader, Quality Control Manager, Summer Research Internship, and Temporary Project Hire.

Module 2: Introduction to Scientific Method

• Forensic is derived from the Latin forum, referring to a marketplace, court and adversarial system of justice.
• Forensic science is also known as Science in the service of law.
• A Forensic Scientist or Criminalist applies criminalistics. Subfields of criminalistics:
  • Biological (blood, tissues, semen, saliva, DNA)
  • Chemical (controlled substances, trace evidence)
  • Pattern Evidence (footwear, fingerprints, document analysis)
• Science used in law has different elements.
  • Criminal litigation involves analysis of physical evidence from the crime scene.
  • Civil litigation involves monetary compensation for error, wrongful consequences, or patent infringement.
  • Forensic policies are standard written procedures and expectations for best practice at local, state, and federal levels.
• Forensic science provides community service and public safety.
• Benefits should exceed costs.
• Physical evidence and analysis is used in the legal system.
• Value comes from the implementation of new technology, and balancing public safety with personal privacy.
• Physical evidence provides information such as elements of a crime (Corpus Delicti)
• Physical evidence can corroborate/disprove statements from victims, suspects and witnesses.
• Physical evidence can identify persons and provide investigative leads
• Physical evidence establishes linkages between victim, suspect, weapon, fruits of the crime, crime scene, and witnesses, or exclusions
• Corpus Delicti is the body or "elements" of a crime needed to prove “beyond a reasonable doubt"
  • Homicide would require the corpse itself.
• Examples of crimes include:
  • Drug possession (illegal substance)
  • Drunk driving (DUI) (0.08% blood alcohol)
  • Sexaul Assault (against will and penetration and jurisdiction dependent definition)
• Physical evidence can either support or disprove witness testimonies.
• Jurors tend to believe eyewitnesses but eyewitnesses are unreliable due to possible memory issues, confusion or lies
• Physical evidence is fixed but is subject to misinterpretation.
• The trier of fact (judge, jury, administrative officer) evaluates physical evidence based on scientific findings in the laboratory.
• Physical evidence analysis can identify materials such as controlled substances, counterfeit currency, and accelerants in fire debris.
• It can also identify Gunshot residue on hands of suspected shooter, and it does this but using classification Methods.
• Physical evidence can identify persons using biological evidence, fingerprints, and the identification of human remains.
  • Analysis includes anthropology (study of skeleton), biometrics (measurements from the body), and DNA (deoxyribonucleic acid)
  • Individualization methods, is a way of asking "Who is it?"
• Physical evidence provides investigative leads that includes or excludes a suspect.
• It rules out unproductive paths, and it aids national database investigation of cold cases.
• CODIS (DNA database), NIBIN (weapons- fired bullets and cartridge casings), and AFIS (fingerprinting)
• Forensic history can be traced back to 1200-1900 AD with early forensics in China in 1250 AD.
• The western world had it's beginnings in 1800-1850
• Scientific approach includes Microscopes and basic human anatomy
• Identification of blood and semen stains were created.
• Toxicology (Orfila 1787-1853) and Criminalistics (Hans Gross 1893) were established.
• The methods include:
  • Anthropometry (body measurements like skull circumference)
  • Fingerprints
  • DNA
  • Biometrics
• Identification using anthropometry began with Alphonse Bertillon in Paris, France, during the 1880s-1890s.
• Bertillon created a system using 11 body measurements on a card with a “portraite parle”. and using an Alias.
• It Helped solved several crimes and invented the mug shot.
• Identification using Fingerprints were later discovered.
  • Henry Faulds and William Herschel created a scientific nature article that showed fingerprints were unique
  • Sir Francis Galton wrote the 1892 book "Fingerprints"
  • Juan Vucetich made the first use of fingerprints to solve a homicide in Buenos Aires.
  • Over time fingerprints replaced anthropometry.
• DNA individualization is now widely used.
  • All but identical twins have unique DNA (Highly informative).
  • Analysis includes direct deposits, secondary transfer, and the use of human database.
  • Methods include iris pigmentation (biometrics) and fingernail striation

Module 3: Fingerprints I and II

• Fingerprints are classified as patent, impressed, or latent.
• There are 3 levels, patterns such as Loops, arches or whorls, Minutiae level and Pores and incipient ridges level.
• ACEV is the methodology used for analysis and comparison of 2 prints.
• AFIS is the automated database search system for matches of possible suspects to unsolved casework.
• The Henry Classification system is an early ratio scoring system for scanning ten print cards for matches.
• Enhancement reagents are classified by porous or nonporous surface use and by what component of the fingerprint the reagents bind to based on chemistry.
• Fingerprints consist of organic and inorganic substances, water, salts, amino acids, and lipids.
• Each Component can be targeted to enhance the image of the fingerprint if a visualization agent is attached.
• Methods for collection of fingerprints from the crime scene require photography, 1:1 image scale, and for use on challenging surfaces/shiny surfaces
• Collections include tape lifts, gel lifts.
• Methods to collect fingerprints from a known person include rolled ink fingerprints of all fingers using scanners.
• Bias is avoided if evidence fingerprints are examined before examining the known reference fingerprints.
• The three main ways fingerprints are classified include:
  • Patent or visible in blood or on shiny surface,
  • Impression on softer substances
  • Latent- requires some form of lighting or chemical enhancement to visualize details
• Enhancement reagents include oblique lighting for surface oils, alternate light sources for fluorescence on porous surfaces.
• Small particle reagent (SMP) is also used on wet surfaces like submerged vehicles.
• Powders (black, white, colored, fluorescent) increase contrast on surfaces.
• Metal shavings/powders are used with magnetic wands for contactless visualization to avoid smearing prints.
• Vacuum metal deposition applies substances that contour to the fingerprint surface under high pressure like metals or glass fibers.
• Features identified and compared in fingerprints include:
  • Loop, Arch, Whorl
  • Minutiae (bifurcations, islands and crossovers)
  • Incipient ridges (thinner, shallower)
• Matching algorithms such as the Henry Classification system (whorl counting) and image recognition (AFIS) are ways to compare prints.
• Fingerprints last 0–4 hours on skin.
• Smooth, hard and oily surfaces can hold good fingerprint details.
• There is no set minimum number of minutiae to compare fingerprints, but agencies may use 8-12 as a lower boundary.
• Immigration officers may require 25-80 minutiae due to the quality of prints taken from a known individual.
• Major Print patterns include:
  • Loop
  • Arch
  • Whorl
• Sub patterns:
  • Tentarch
  • Double loop
  • Pocket loop
  • Mixed
• Level 1 features
  • Arch, left loop and right loop
  • Double loop
  • Whorl.
• Level 2 features
  • Line unit, line fragment, ending.
  • Bifurcation
  • Eye, and hook.
• Level 3 features
  • Pores
  • Line shape
  • Incipient ridges
  • Creases
  • are all uniques to fingerprints
  • Warts
  • Scars
• Prints don't change unless damaged.
• The Henry ACEV system helps match prints and recognize changes from crime scene.
• Friction occurs with fingertips palms and Soles. Includes Hills and Valleys, Ridges and Furrows plus Genetics and wear patterns
• Minutiae are compared between print patterns.
• Ridges form minutiae by doing the following, Ending abruptly (end ridge) and splitting (bifurcation) and being short (dot)
• Types of pattern can be categorized as
  • Arch (plain, tented)
  • Loop (ulnar, radial)
  • Whorl (plain, central pocket loop)
  • Core and delta Points
  • Ridges
• Pattern area of loops or whorls have a core, deltas, and ridges enclosed by type lines.
• Ridge characteristics include ridge endings, bifurcations, lake and dot.
• AFIS (automated fingerprint identification system) creates scanned, digitized image which produces: .
• 1:1 imaging that eliminates suspect matches and compares ridge patterns.
• Partial print matching which will match line angles, positions and it is not reliant on primary pattern
• FBI processes 40,000 per day.
• Quality in prints can be improved if there is an understanding of how each situation causes a different visual end product.
  • Too much pressure, too little or too ink ink, dirty/cold fingers.
• Rolled prints are applied broadly from one side of an inked plate and should press lightly.
• Fingertips are all rolled again bottom the top.
• Palms are inked broadly pushing the hand forward to stretch out fingers.
• Dusting requires:
  • Soft hairs
  • Powders with fine structures, tapes, or elastic
  • Magnifier and white/black tape.
• Exceptions to persistence of uniqueness to a fingerprint are:
  • Medical conditions such as Dysplasia or Psoriasis caused by age, diseases, genetic predispositions, or wound healing.
• Collection methods include:
  • Sidelight
  • Flashlights
• Forensics are aided by:
  • Xeons
  • ALS
  • Image enhancement that results in documents or good quality photography
  • Bright lights and chemical treatments cause contrasts.
• The following are used for enhancing latent fingerprints, by collecting Moveable object
• Physical methods use dry surfaces and colored powders, then the application bonds with sweat.
• Chemical Treatments consist of liquids that affect the surface
• Iodine fuming (porus/nonporus)
• Vacuum method: affect later stages of photography
• Inert Powder are best for nonporous surfaces
• Photography aids include Nonreflective surfaces
  • Lasers adhere to the image
  • X-rays adheres to lead for plastic films
  • Gold and silvers adhere to prints

Module 4: Firearms and Toolmarks

• Types of firearms include rifles, shotguns, handguns which include muzzleloader and breech loader.
• Types include: lever, bolot, pump, revolver, semi auto, auto, handheld, mechanical and manual
• Barrel rifling results in the transfer of marks on the bullet as it passes, and from actions such as being hit with the firing pin. This creates impressions and indentations.
• Caliber is diameter of bullet. 30 hundredths is a .30 caliber bullet.
• A comparison microscope is used to check marks.
• Examination with microscope uses 5x - 40X to orient bullets
• Two sets of objectives connected by an optical bridge to compare evidence to test fire images
• Image databases helps collect evidence of above.
  • NIBIN (national integrated ballistic information network) shares images of ballistic evidence.
  • Brasscatchers are an apparatus used to capture shells.
• GSR (gunshot residue) is material found around surface of victim.
• SEM reveals electrons generated by two processes and x-rays.
• The process is nondestructive at 1000000X.
• Analysis reveals GSR, defined by Pb, Sb and Ba characteristics.
• Analysis also uses Reagent (Griess), and Sodium and chromatography
• GSR patterns helps determine the range of what was detected and patterns.
• Tool Marks is a comparison of indentations in the tool used.
• A striker is placed on an object usually rough and irregular, parallel striations in a direction of movement.
• Individual marks such as serial numbers and logo are identified as a source.
• Identification is when there is a match.
• Exclusion is when evidence definitely does not belong.
• Inconclusive means unclear for source.
• Transferred evidence includes fingerprints, paints, blood, DNA, fibers to connect crime.
• Computerized database helps match toolmarks.
• Matching determines injuries based on serations, width, length, force to document injuries.

Module 5A: Questioned Documents

• Components of this include analyzing ink and paper used.
• This includes analysis of types of writing, as well as Protection against forgery plus ransom notes cases
• Positions include field investigator, document examiner plus attorney.
• Civil plus criminal are included. Also covers Personnel issues in security, investigations, harassment
• Exam can occur with Microscope from 1970's to present in types such as:
  • Roller pens/Porous tips
  • Electronic/Single elements
  • Dry process
• Instruments used to prepare documents include: -Nib-ancient -Steel dip pen -Stylographic fountain pen -Ball point
• Analysis includes both soluble/insoluble items
• Inks were tested like those from fiber/ roller ball pens
• Similar pen types are compared versus those of handwriting, samples etc to question document
• At the minimum test can determine that is consistent with the original.
• Waxy chemicals can identify substances written outside original source
• Ancient inks were: carbon, iron-gall, modern blue-black
• Synthetics started at a later point: aniline
• Date stamps helps verify doc versus ink
• Testing occurs with chromatography
• Examination occurs with luminesce or with filters
• 1st step, conduct without destruction tests. To conduct sunlight, uv tests.
• 2nd step, microscopic spot test: drop of chemical reagent on a portion of ink stroke using iron and carbon.

Module 5B: Computer Forensics

• Computer forensics uses digital and archived images and data in investigations.
• Investigations occurs because trafficking in drugs, humans, firearms, and pornography is illegal/trafficked.
• Ability to track and trace is hampered by coding, use of intermediate distributors, such as bitcoin.
• Checking hard drives happens when authorities do not know who accessing the data
• Visible and latent data analyzed on trade sites, ebay, and websites associated with illegal materials.
• Silk road is an investigation of illegal goods and owner/developer
• Computers can then create images such as in forensic DNA phenotyping for predictive phenotyping from DNA
• One can reconstruct faces from genetic material from Paragon Nanolabs

Module 7: Medicolegal

• Medicol Cases include several categories. Accidents, allegatations, burns, intoxication and animal attacks.
• Other cases: unconscious, abortion, reactions plus a death.
• Points to remember are examination must occur and not be refused. Also to document that the medical professional will not delay and seek treatment with consent. All details are checked with the same examiner. Documentation should be completed at point to mention full name.
• Always document after the case as all documents should bare MLC Number.
  • Address, gender and notes taken for follow up.
• Details should be precise plus clear and always accurate with a full document
• Consent must occur and without would equal assault
• If death certificate is applicable it is a known cause.
• Malpractice is negligent when a reasonable man guided by those ordinary considerations which

Learn about applying the scientific method in forensic science. Includes hypothesis creation (e.g., in criminal cases) and legal implications. Reviews observational research, data collection at crime scenes, evidence analysis, and user testing of forensic methods.