DIVISIONS OF FORENSIC SCIENCE

1. Criminalistics, 
2. Digital and Multimedia Sciences, 
3. Engineering Sciences, 
4. General, 
5. Jurisprudence, 
6. Odontology, 
7. Pathology/Biology, 
8. Physical Anthropology, 
9. Psychiatry/ Behavioral Sciences, 
10. Questioned Documents, 
11. Toxicology

TYPES OF CRIME LABS

• National/Federal (Ex: FBI)
• State (Ex: SLED)
• Local (Ex: RHPD, CMPD)

CRIME LABS

Full service Labs must contain:

Physical Science Unit, Biology Unit, Firearms Unit, Document Examination Unit, and Photography Unit

CRIME LABS

Other services may include:

Toxicology Unit, Latent Fingerprint Unit, Polygraph Unit, Voiceprint Analysis Unit, or Crime Scene Investigation Unit

CRIME LABS

Services that are not part of a typical crime lab include:

Forensic Psychiatry, Forensic Odontology, Forensic Engineering, and Forensic Computer & Digital Analysis

DUTIES OF A FORENSIC SCIENTIST

1. Analysis of physical evidence

• Strict guidelines, applies the scientific method to answer questions about the evidence
• Evidence must be admissible to be used in court (Frye Standard, Daubert Ruling)

DUTIES OF A FORENSIC SCIENTIST

2. Provide expert testimony

• Must show that you are qualified to testify as an expert (based on degrees, special coursework, # years experience, publications, and/or membership in professional societies)
• The testimony:  Provides opinions about the evidence and techniques applied based on expert knowledge (advocate for the truth – discuss all aspects of the analysis)

PHYSICAL EVIDENCE

• Objects that can establish whether a crime has occurred or not or that can link crimes, victims and perpetrators
• Trace evidence – small and sometimes not readily apparent

SECURE AND RECORD THE CRIME SCENE

Obtain medical assistance, Evaluate the victim, Identify/detain potential witnesses/suspects,  Arrest the perpetrator (if known), Note vehicles/people coming into/leaving the scene, Isolate the scene with ropes or barricades to preserve from intruders, Identify all individuals at the scene

SECURE AND RECORD THE CRIME SCENE

Define the perimeter, look for entry/exit sites, initial walk through to identify obvious evidence, strategy for the investigation, notes of the crime scene in original condition

Recording the Crime Scene – three components

• NOTES- Should contain all information gathered from the time a call is received
• PHOTOGRAPHY- Shows the crime scene from all angles in an unaltered state (before evidence is removed) and adjacent areas (digital photos can be manipulated – have to show that they weren’t)
• VIDEO- Can be useful to combine notes and photo (may sacrifice quality)

• SKETCHES- Shows the overall layout of the crime scene and the space relationship of all relevant items (entry, exit, evidence)
• Rough sketch- done at the scene, must contain accurate measurements & legend
• Final sketch- prepared from rough sketch using software, neater version

SEARCH FOR, COLLECT AND PACKAGE EVIDENCE

Search Patterns (must be thorough to locate all physical evidence):

• Strip/line search –back and forth
• Grid search –back and forth, then in other direction
• Spiral search –circle around and around
• Wheel/ray search –in or out (can miss areas between)
• Quadrant/zone search –subdivide a large area

SEARCH FOR, COLLECT AND PACKAGE EVIDENCE

• Evidence should be collected with gloves and packaged in appropriate containers for the type of evidence
• Items that may contain “touch DNA” (DNA transferred when someone touched an item) should be collected

FOLLOW THE CHAIN Of CUSTODY

• Chain of custody - record that documents every person who has had possession of the evidence
• This should be limited to as few people as possible and must be signed/initialed by every person

TAKE REFERENCE SAMPLES

• Often, evidence must be compared to known standards or reference samples
• These may be taken from the crime scene, victim, or suspect or may be known sources
• Substrate controls are samples collected adjacent to or nearby areas containing evidence

SUBMIT EVIDENCE

• Evidence should be numbered and packaged separately for identification purposes
• An evidence submission form with all evidence listed should accompany the delivery

• Infectious materials (blood/bodily fluids) pose health risks to investigators
• Precautions:
• Wear double gloves, shoe covers, coveralls, masks, goggles, face shields
• Watch out for sharps and package in sturdy container
• Make sure you’ve had Hepatitis B vaccination
• No eating, drinking, or smoking while in area
• Contaminated materials should be disposed of  in biohazard waste containers

LEGAL CONSIDERATIONS

• Evidence can be thrown out if a judge determines that it was acquired in an illegal search
• No warrant is required if: Emergency circumstances exist, There is immediate danger of loss or destruction of evidence, The search occurs along with lawful arrest or Consent is given by involved parties

ROLE OF PHYSICAL EVIDENCE

Physical evidence is examined to IDENTIFY or COMPARE

IDENTIFICATION:

Aim to determine the physical/chemical identity of a substance with as much certainty as possible

COMPARISON: 

A piece of evidence and reference sample are tested using the same methods to compare and determine if they have a common origin

INDIVIDUAL VS. CLASS CHARACTERISTICS

• INDIVIDUAL: Characteristics that are unique to a piece of evidence, sometimes difficult to identify
• CLASS: Characteristics that items in a class or group all have in common; easy to identify
• Note: a large number of common class characteristics increases the probability of common origin between two objects

FORENSIC DATABASES

• Allows comparison of current evidence to known profiles of evidence from previous crimes
• FINGERPRINT DATABASES
• IAFIS : Integrated Automated Fingerprint Identification System (FBI)
• AFIS – state fingerprint databases, linked to IAFIS
• DNA DATABASE à CODIS : Combined DNA Index System (FBI)
• OTHER DATABASES
• NIBIN: National Integrated Ballistics Information Network (ATF)
• PDQ : International Forensic Automotive Paint Data Query Database
• Maintained by Forensic lab of the Royal Canadian Mounted Police
• SICAR: Shoeprint Image Capture and Retrieval 

DEATH INVESTIGATIONS

• The most important piece of forensic evidence is the body
• Conducted in cases of sudden, unnatural, unexplained or violent deaths
• Forensic Pathologist: medical professional (M.E., Coroner) who applies forensic science to a body
• Attempts to determine cause, manner and time of death
• Who is the victim? What injuries are present? When/how did injuries occur?
• Manner of death? Natural, homicide, suicide, accidental, or undetermined

TIME OF DEATH

• Stages of decomposition can help establish timeframe
• Several processes involved in decomposition:
• Rigor mortis: Stiffening of muscles
• Livor mortis: Blood settles to parts of body facing the ground (gravity; skin discolored)
• Algor mortis: Cooling of body to ambient temperature

FORENSIC ANTHROPOLOGIST

• Identifies and examines human skeletal remains
• Bones can reveal information about gender, age, race and skeletal injuries
• Gender – especially pelvic bones and skull
• Age – based on length of long bones or fusion of other bones in children or wear on bone in adults
• Race – a likely racial ancestry can be determined based on broad classes of cranial characteristics

FORENSIC ENTOMOLOGIST

• Studies insects and their relationship to a criminal investigation
• Commonly use the stage of insect development or types of insects present to establish time of death
• Necrophilious insects – feed on dead tissue; infest a body within 24 hours (ex: blow fly)
• Others arrive later and sometimes in a specific sequence
• The insects can be sampled as to
• look for drugs or toxins that may
• have been in the victim’s body

PROPERTIES

•  Properties are the identifying characteristics of substances
• There are two categories:
• Physical: describes a substance without reference to any other substance (weight/mass, color)
• Chemical: describes the behavior of a substance when it reacts or combines with another substance (ex: chemical tests for presence of certain drugs)

THE METRIC SYSTEM

• Standard system of measurement used in the scientific community
• In the metric system – all units are multiples of 10, so conversions only require moving a decimal

METRIC CONVERSIONS

• In the metric system, there are base units for each type of measurement:
• Length             meter (m)
• Volume            liter (l or L)
• Mass                 gram (g)
• To convert from the base unit to a smaller or larger unit, you simply change the prefix and move the decimal

ENGLISH TO METRIC CONVERSIONS

• Since measurements at a crime scene will often be recorded in English units, they will need to be converted to metric units in the lab to compare and draw conclusions
• Use the method we learned in lab to perform these conversions.

PHYSICAL PROPERTIES

• Temperature – Heat intensity (Two scales: Farenheit or Celcius)
• Weight and Mass
• Weight: force with which gravity attracts a body
• Mass: amount of matter an object contains (independent of gravity)
• Density (Mass per unit volume (g/ml))
• Density of a substance is always the same, regardless of the size
• Can be used to identify a substance
• Refractive Index- Bending of light rays due to a change in medium; Can be used to identify a substance

COMPOSITION OF GLASS

• Glass is a hard, brittle, and amorphous substance
• Variations
• Soda glass – sodium carbonate is added (dissolves in water)
• Soda-lime glass – calcium oxide is added (most common)
• Heat-resistant glass – boron oxide added
• Tempered glass – rapid and repeated heating and cooling; prevents glass from shattering when broken
• Laminated glass – two sheets of glass with plastic between; used for windshields

ANALYZING GLASS FRAGMENTS

• Only SURE way to determine the source of the glass is to piece together with the original source
• Can examine density and refractive index

GLASS FRACTURES

• Can sometimes tell you about the force and direction of impact
• Two types of patterns produced when glass is penetrated:
• Radial Fractures – radiate outward from point of impact
• Concentric fractures – encircle the hole at the point of impact

COLLECTION & PRESERVATION OF GLASS EVIDENCE

Collect ALL of the glass at a crime scene and reference glass for comparison, package in solid containers to prevent further breakage and collect shoes, clothes or other items that may be carrying glass evidence

FORENSIC ANALYSIS OF SOIL

Soil can contain rocks, minerals, vegetation, animal matter, glass, paint chips, asphalt, brick fragments, and/or cinders - the combination of components can make soil unique to a certain area

EXAMINATION OF SOIL

• Gross appearance (Color (must be dried), Texture)
• Microscopic appearance
• Low power: look for plant or animal derived material
• High power: characterize minerals/rocks

COLLECTION & PRESERVATION OF SOIL EVIDENCE

Package 1-2 Tbsp from the surface in individual containers (plastic vials)

• Matter is anything that has mass and takes up space
• Elements: Building blocks– can’t be chemically broken down any further
• Atoms : Smallest units of elements
• Matter has three states (forms): Solid, Liquid, Gas

ORGANIC AND INORGANIC COMPOUNDS

• Organic molecules contain carbon and hydrogen
• Inorganic molecules are not carbon/hydrogen-based

ANALYTICAL TECHNIQUES

• Can be:
• Quantitative: applies a numerical measurement (% of a substance in a mixture)
• Qualitative: describes or identifies a substance (components of a mixture)

TYPES OF TECHNIQUES USED IN FORENSICS

• Chromatography – separates components of a mixture
• Spectrophotometry – analysis based on the substance’s absorption of light
• Emission spectra – analysis based on the substance’s emission of light

CHROMATOGRAPHY

Techniques where components of a mixture are separated from each other and identified    

Three common types of chromatography:

• Gas chromatography:  Components of a mixture separate by the carrier gas and move through the column as temperature increases
• High pressure liquid chromatography:  A pressurized liquid phase moves over beads containing the mixture and separation occurs based on solubility in the solvent(s) and interactions with the beads
• Thin layer chromatography: Mixture is separated based on the solubility of components in the solvent
• Electrophoresis can also be considered a type of chromatography:  Most useful for analysis of DNA.  Smaller pieces or fragments of DNA move fastest

SPECTROPHOTOMETRY

Spectrophotometry is the characterization of substances based on their ability to absorb and reflect certain wavelengths/ colors of light

MASS SPECTROPHOTOMETER

• Combined with a gas chromatograph, the mass spectrophotometer can specifically identify substances
• GC separates components and the MS fragments components to identify their masses –unique pattern
• Useful in the identification of drugs

• Non-carbon based molecules (make up most of the earth’s crust)
• Trace elements are often inorganic and may provide individual characteristics

Microscopes are instruments with: 

The compound microscope has: 

MAJOR SYSTEMS OF A COMPOUND MICROSCOPE

• There are two major systems of a microscope
• Mechanical System (Base, Arm, Stage, Body tube, Coarse and fine focus)
• Optical System (Illuminator, Condenser, Objective lenses, Ocular lenses)

MAGNIFICATION

• Magnification: ratio of the size of the image to the object’s actual size
• Oculars magnify 10 times (X)
• Objectives magnify 4X, 10X, 40X, and 100X (oil immersion)
• Total magnification = ocular mag X  objective mag

TYPES OF MICROSCOPES

COMPARISON MICROSCOPE:

Allows side-by-side comparisons of two objects or samples

TYPES OF MICROSCOPES

STEREOSCOPIC MICROSCOPE:

• Lower magnification than compound microscope, but you can see objects in 3 dimensions with wider field of view and depth of focus
• Uses in a forensic lab: 1) locate trace evidence in debris or on garments, weapons or tools or 2) to analyze or characterize paint, soil, gunpowder residues and marijuana leaves

TYPES OF MICROSCOPES

POLARIZING MICROSCOPE:

TYPES OF MICROSCOPES

MICROSPECTROPHOTOMETER:

TYPES OF MICROSCOPES

ELECTRON MICROSCOPES:

aim a beam of electrons at sample to magnify up to 100,000X w/ good resolution

Drug =

a natural or synthetic substance used to produce physiological or psychological effects in humans

DRUG DEPENDENCE

• Drug dependence is the “habit-forming” quality of some drugs.
• Psychological dependence: due to improved sense of being that develops when taking the drugs
• Physical dependence: characterized by physical illness once the drug is withdrawn

DIFFERENT TYPES OF DRUGS

Narcotic

• a drug that brings relief from pain and produces sleep.
• This term is often used incorrectly to describe any drug that is socially unacceptable

DIFFERENT TYPES OF DRUGS

Opiates

DIFFERENT TYPES OF DRUGS

Hallucinogens

DIFFERENT TYPES OF DRUGS

Depressants

drugs that slow down or suppress the central nervous system

DIFFERENT TYPES OF DRUGS

Stimulants

drugs that speed up or stimulate the central nervous system

DIFFERENT TYPES OF DRUGS

Club drugs

a group of drugs that are used in nightclubs, bars, raves, etc. to magnify the experience

DIFFERENT TYPES OF DRUGS

Anabolic steroids

used to accelerate muscle development

DRUG CONTROL LAWS

• Impose specific requirements for analysis of drug evidence and attempt to prevent and control drug abuse
• Controlled Substances Act –Classifies drugs in schedules based on potential for abuse and dependence weighed against possible medicinal use

DRUG IDENTIFICATION

Screening tests

tests used to determine the possible identity of a drug (often color tests)

DRUG IDENTIFICATION

Confirmation tests

a single test that identifies a drug (GC-MS, IR-Spec)

DRUG IDENTIFICATION

Quantitative tests

test that determines the concentration of drug in a mixture

COLLECTION OF DRUG EVIDENCE

Collect ALL drug evidence and prevent loss of material, prevent cross-contamination, package solvents in airtight containers, properly label all packaging

TOXICOLOGY

Detection and identification of drugs and poisons in body fluids, tissues and organs

ALCOHOL IN THE BODY

• How alcohol travels in the body: consumed as a drink, absorbed into the blood from the stomach and small intestine, circulates in the bloodstream and can diffuse into the air spaces in the lungs, eventually reaches the brain and creates effects
• Factors that affect the absorption rate of alcohol: Size/weight of person, Recent meal, Type of beverage consumed (alcohol content), Amount consumed and how quickly
• Alcohol elimination is due to breakdown by liver and excretion through breath, urine, and perspiration
• Concentration of alcohol in breath is comparable to concentration in blood which is comparable to concentration in brain.

ANALYSIS FOR ALCOHOL CONTENT AND CONCENTRATION

• Take brain or vitreous humor (found in eye) sample (only in an autopsy)
• Take a blood sample (in a lab setting) to be tested by gas chromatography
• Measure alcohol in breath (can be done anywhere)

TESTS FOR INTOXICATION

• Breath tests
• Field sobriety tests – determine impairment
• Horizontal gaze nystagmus: follow a pen light –look for side to side jerking of the eye
• Walk and turn –walk toe to toe, turn, and walk back toe to toe
• One-leg stand –stand on one foot, keep body balanced & count out loud for 30 seconds

PROPER COLLECTION AND PRESERVATION OF BLOOD ALCOHOL EVIDENCE

Blood should be collected by swabbing skin with non-alcoholic antiseptic, venous puncture, blood collection in a tube with preservative and anti-clotting factor, stored at refrigeration temperature

ROLE OF A FORENSIC TOXICOLOGIST

• Forensic toxicologists examine samples (bodily fluids, clothing, containers, etc.) for drugs and poisons and determines the concentration
• Because of metabolism of drugs and poisons, the forensic toxicologist may be looking for derivatives or by-products of chemicals

TOXICOLOGY TECHNIQUES

• Chemical is characterized by pH (Acid/Base)
• Analytical tests are run (GC/MS)
• Non-Drug poisons
• Heavy metals detected by inorganic analysis techniques
• CO (carbon monoxide) detected by measuring CO bound to hemoglobin of RBC

DRUG RECOGNITION EXPERTS

• Drug recognition expert requires special training to recognize signs of drug intoxication
• Type of physical impairment is evaluated and documented- gives an idea as to type of drug used.
• Depressants
• Stimulants
• Hallucinogens
• Dissociative anesthetics
• Inhalants
• Narcotic analgesics
• Cannabis

FORENSIC SEROLOGY

Forensic serology is the use of blood, semen, saliva, and other bodily fluids in the investigation of legal matters

BLOOD

• Blood = fluid + cells + dissolved molecules
• Plasma is the fluid of blood and serum is plasma with the clotting factors removed
• The cells of blood are Red blood cells (RBC) and  White blood cells(WBC) (Platelets- cell fragments)
• Dissolved molecules include antibodies (antibodies are Y-shaped proteins that are stick to foreign objects-they are made by the immune system)

BLOOD ANTIGENS AND ANTIBODIES

• Red blood cells contain molecules on the surface called antigens
• These molecules are used to determine a person’s blood type
• Antibodies are Y shaped proteins made by the immune system to attack foreign substances    

• Blood typing is a set of techniques where the molecules on red blood cells are characterized
• There are 15 different blood groups that have been identified so far
• We use ABO blood group plus Rh factor
• Questioned blood is mixed with anti-serum that contains antibodies (against A, B, and Rh)
• RBC with that antigen will agglutinate (clump together) when mixed with the anti-serum

FORENSIC CHARACTERIZATION OF BLOOD

1. Is it blood?
2. Is it human blood, or another species?
3. If human blood, can it be associated with a particular individual (suspect or victim)?

Use blood typing (weak) or DNA profiling (strong)

TESTING FOR PRESENCE OF BLOOD

• Tests are designed to look for the presence of hemoglobin (the iron-containing molecule of RBC)
• Kastle-Meyer test (phenolphthalein) + suspected bloodstain sample + peroxide = pink color change
• Hemastix test: green color change in presence of blood
• Luminol: light reaction seen in dark
• Bluestar: light reaction seen in dark

PRECIPITIN TEST

Used to determine if a blood sample is of human or animal origin

GENETICS AND HEREDITY

• All cells of a living thing (with a few exceptions) contain chromosomes made of DNA
• Chromosomes contain genes – the units of heredity that determine your traits
• In humans, there are 46 chromosomes in each body cell except the sex cells (also called gametes) such as sperm and eggs (23 each)
• There are 2 copies of each chromosome –one inherited from your mother and one from your father
• If you are a male, you have an X and a Y chromosome
• If you are a female, you have 2 X chromosomes
• Genes are pieces of the DNA which code for a particular protein, which gives you a trait
• There are different versions of each gene which are called alleles

SEMEN TESTS

• Most common in crimes involving sexual offenses
• First, must locate the potential semen stains (Usually found with light source or by visual inspection)
• Then subject to testing to confirm
• Acid phosphatase test –chemical test for presence of semen (fluorescence with UV light)
• Microscopic examination for sperm (spermatozoa)
• PSA test –prostate-specific antigen

SPERM

DNA

• DNA = deoxyribonucleic acid = genetic information in cells
• It determines what characteristics any organism has
• DNA can be used to identify the origin of a biological sample

DNA STRUCTURE

• Composed of units called nucleotides
• Each nucleotide contains a sugar, phosphate group and a base
• The bases are represented by the letters A, T, G, and C
• The bases pair with each other in a specific way across the double helix of DNA
• A bases always pair with T bases
• G bases always pair with C bases

GENETIC CODE

The sequence of bases along a strand of DNA gives the “code” for the cell to make a protein    

DNA REPLICATION

• Since the bases of DNA pair in a certain way DNA can be copied (before a cell divides)
• The two strands of DNA are broken apart then two new strands are built using the sequence of the two old strands as a guide

PCR

• PCR = polymerase chain reaction
• Uses the same concepts involved in DNA replication – in a tube!
• This technique allows the copying of a single piece of DNA to make millions of copies
• After PCR, the DNA can be typed or profiled

PCR PROCESS

• PCR goes through many cycles – in each cycle the DNA doubles
• Steps of each cycle: Denature (DNA separates), Anneal (primers bind to DNA), Extend (DNA is copied)

DNA TYPING TECHNIQUES (Also DNA Fingerprinting or DNA Profiling)

• The DNA typing techniques analyze parts of human DNA where there is variability
• RFLP –all DNA from cells is chopped up and analyzed.
• STR –short tandem repeats; amplify regions by PCR and look for size differences.
• Multiplexing –amplifying and analyzing many STRs at one time.
• Sex determination –use the amelogenin gene to tell the difference between male and female.
• DNA can be separated by gel electrophoresis and when stained can be seen as dark bands

HOW CAN STR’S Be USED?

• DNA Profiles
• Paternity Testing
• An example of paternity test results.
• Read the column of DNA bands for the child. In the child’s profile, one band must come from the mother’s profile and one band from the father.

CODIS

• CODIS = Combined DNA Index System
• Set of databases that contains DNA information from convicted offenders and arrestees (from some states), human remains, forensic casework, missing persons, etc.
• CODIS uses 13 different STR locations (loci) in human DNA for comparison

MITOCHONDRIAL DNA

• Mitochondria are small organelles (compartments) in cells that contain very short pieces of their own DNA
• You inherit mitochondria only from your mother (from her egg) so your mtDNA is exactly like your mother’s
• USE OF mtDNA
• You cannot identify a specific person using mtDNA
• You can identify a family to whom mtDNA belongs

COLLECTION AND PRESERVATION OF DNA EVIDENCE

• Photograph location of possible DNA evidence
• Handle all biological evidence with gloves to prevent contamination of it – change gloves often!
• If you want to preserve DNA, you must let it dry out –do not package in airtight containers!!!
• Reference samples of DNA
• Usually buccal swabs are collected by swabbing the inside of the cheek
• Blood may also be collected and preserved on specially treated paper

BLOOD SPATTER

• Blood spatter = drops of blood left behind when it moves from an individual or an object and hits a surface
• Blood spatter patterns can tell you: Direction from which blood originated, Angle at which blood drop struck a surface, Location/position of a victim, Movement of a bleeding individual, Minimum number of blows, Approximate location of person delivering blows

Gunshot spatter

caused by fine drops of forward and backward spatter as a result of a gunshot

Cast-off spatter

caused by a blood-covered object throwing off blood drops as it moves

Arterial spray spatter

caused by an injury to a person’s artery, usually curved or arced

Expirated blood patterns

caused by blood coming out of nose and/or mouth,  bubbles dried in blood

Void patterns

caused by an object getting in the way of spatter, empty area

Contact/transfer patterns

caused by an object leaving a pattern in blood

Flows

caused by blood flowing by gravitational pull

Pools

caused by blood collecting in one area

ANALYSIS OF BLOOD SPATTER

• Determine velocity
• Determine direction of travel: Tail of the drop faces the direction of travel
• Angle of travel: Measure Length and width of drop (Angle = sin^-1 (w / l))
• Area of origin – use string method as discussed previously

HAIR MORPHOLOGY

• Hair has three layers
• Cuticle – outer covering, scaly
• Cortex – inside the cuticle, contains pigment granules (color)
• Medulla – canal in the center of the hair, may or may not be present
• The length of the hair is divided into regions (Root, Shaft, Tip end)

HAIRS AS EVIDENCE

• It is not possible to individualize a human hair to a single individual based on morphology
• Types of information you can get from hair evidence:
• Human or animal origin
• Hair color or structure (length, diameter, medullary index, medulla shape)
• If follicular tissue is present on root – may be able to use for DNA

COLLECTION AND PRESERVATION OF HAIR EVIDENCE

• Must collect hairs into separate folds of paper or containers
• Clothing or other items that may contain hair evidence should be packaged carefully and separately to allow examination in the lab
• Reference samples must be collected from the victim and suspect(s)
• Evidence and reference samples will be compared with a comparison microscope

EXAMINATION OF FIBER EVIDENCE

• Fibers can be Natural or Synthetic
• Natural – found in nature (Examples: Wool, cotton, silk)
• Synthetic – manufactured or man-made (Examples: Polyester, nylon, acetate)
• Side by side examination of crime scene and reference fibers
• Color and diameter, Striations, De-lustering particles, Cross sectional shape, Dye composition, Chemical composition of fiber, Optical Properties

SIGNIFICANCE OF FIBER EVIDENCE

• No way to definitively determine the origin of fiber/fabric evidence unless two pieces of fabric can be matched along a tear
• Usually only individual fibers are found at crime scenes (trace evidence)
• Can try to determine prevalence and probability of other individuals possessing the same fibers (very difficult in most cases)
• Rare fibers increases the strength of association
• Fiber evidence is often used to support other types of physical evidence

COLLECTION AND PRESERVATION OF FIBER EVIDENCE

• Must preserve potential carriers (clothing) and handle with care, package separately
• Visible fibers should be removed with forceps and packaged in folded paper for transport to lab

PAINT EVIDENCE

• Very important in hit-and run cases.
• Transfer of paint is common (between automobiles, automobile to person)
• Analysis of paint can help solve a crime
• Can determine origin of a paint sample by comparing to a sample from a suspect vehicle
• Sometimes, paint analysis can give information about the make, model and year of a vehicle
• Methods of analysis: Microscopic examination, Chemical analysis, Characterization of pigments in paint

Types of automotive paints

• Electrocoatprimer –epoxy resin electroplated onto a car before painting to prevent rust formation. Color is black to gray.
• Primer surfacer–coat to smooth out the surface. Color depends on the topcoat. Light gray for pastels and red for a dark color paint.
• Basecoat –color coat of paint.
• Clearcoat–improve glossy appearance of basecoat

MICROSCOPIC EXAMINATION OF PAINT

Microscopy allows magnification of paint chips to better see the color and layers of paint present

CHEMICAL ANALYSIS OF PAINT

• Pyrolysis gas chromatography is useful in chemically analyzing paint
• IR Spectroscopy can also be used to identify inorganic components of pigments

CHARACTERIZATION OF PIGMENTS IN PAINT

• PDQ= Paint Data Query
• Database of all automobile manufacturers’ paint samples since 1973
• Maintained by the Royal Canadian Mounted Police
• Can identify the make, model, and year of a vehicle for a particular automotive paint sample

COLLECTION AND PRESERVATION OF PAINT EVIDENCE

• Collect with a clean knife or scalpel and pick up with forceps (tweezers), carry in folded paper, glass vials, or plastic vials, collect a standard or reference sample, label the evidence with exact location
• Tools used in crimes may also have paint evidence on them. These should be carefully collected and preserved. Reference samples should be taken from an area of the house/car/etc. near where the tool was used.

ARSON INVESTIGATIONS

Arson:

FIRE

• Fire is a combination of heat and light
• Three requirements for fire: Fuel source, Oxygen gas (O2), Ignition source

SEARCHING THE FIRE SCENE

Investigation begins as soon as fire is extinguished

• Accelerants will evaporate within hours to days
• Evidence should be collected before cleanup/salvage
• Overrides the need to obtain a warrant

SEARCHING THE FIRE SCENE

The investigator looks for:

• Signs of the use of accelerants (chemicals used as fuels to start fires, such as gasoline)
• Irregular shaped patterns where accelerant may have been poured
• Ignition devices
• Signs of breaking and entering
• Witnesses

SEARCHING THE FIRE SCENE

Must identify the point of origin first

• Look for area of most intense burning
• The structure of the building must also be taken into consideration as fire travels rapidly up stairwells, through attics, etc.
• Look for “streamers” – used to connect different areas
• Before any evidence is collected, record the scene (notes, sketches, photos)

COLLECTION AND PRESERVATION OF ARSON EVIDENCE

• 2-3quarts of ash/soot debris including porous materials which would soak up accelerants
• Package in airtight containers, ex. new, clean paint cans or glass jars with tight-fitting lids

COLLECTION AND PRESERVATION OF ARSON EVIDENCE

What to collect

• Collect substrate (uncontaminated) controls –ex. flooring where no accelerant was likely used
• Collect igniter, if found
• Collect clothing of suspect(s)- accelerants could be detected

ANALYSIS OF FLAMMABLE RESIDUES

• Gas chromatograph (GC) is the best instrument for detection of hydrocarbons (petroleum products such as gasoline) used in arsons
• If multiple accelerants were mixed, may be difficult to identify using GC alone
• Using a GC-Mass Spec, can separate the components into individual patterns

EXPLOSIONS

• Explosions are similar to fires but much more rapid - causes disruption of the physical environment
• Explosion cases are investigated by ATF

EXPLOSIONS

Two types of explosives

• Low explosives –decompose slowly; produces a propelling motion
• High explosives –detonate instantaneously with a smashing or shattering effect

SEARCHING THE EXPLOSION SCENE

• Investigation begins at the crater (the origin of the explosion)
•  Thorough search of the entire blast area may provide evidence of chemicals used, detonators used, pieces of the container/vehicle, etc.
• Use of ion mobility spectrometer (IMS) can be used to detect explosives on surfaces
• All evidence should be packaged separately in airtight containers

ANALYSIS OF EXPLOSIVES EVIDENCE

• Microscopic examination first to detect particles of the explosive material
• Debris is rinsed with water or acetone (depending on suspected explosive)
• This rinse can be tested: Color change reactions, TLC, HPLC, GC-MS, IR Spectrophotometry, X-ray Diffraction

A fingerprint is a 

• permanent folds in the skin that contain sweat glands
• Dermal papillae between epidermis and dermis
• Develop in the fetus – grow but don’t change

Fingertips leave 

FINGERPRINTING

FUNDAMENTAL PRINCIPLES:

• 1. A Fingerprint is an individual characteristic (unique)
• 2. A fingerprint remains unchanged during a person’s lifetime
• 3. Fingerprints have general ridge patterns which allow classification
• Loops –ridges come in from one side of the finger and exit the same side
• Arch –ridges come in from one side, go up, peak, and come back down and go out the opposite side of the finger
• Whorl –ridges go around in a circle

AFIS

• Automated Fingerprint Identification System operated by FBI
• States and local governments have their own systems – all linked to FBI
• Integration of them is called Integrated AFIS or IAFIS

AFIS

how it works:

• Digitally encode prints- identify minutiae
• Processed by computer algorithm
• Compared location and relationship of minutiae to suspect database
• Generates list of candidates – manual confirmation using point by point comparison of minutiae
• Dramatic impact on “No suspect” cases

TYPE OF PRINTS LEFT AT A CRIME SCENE

• Visible prints –fingerprints that can be seen; usually left in blood, paint, etc.
• Plastic prints –impressions left behind of fingerprints
• Latent prints –invisible fingerprints

• Photograph first! This records the print location and detail (if possible)
• If possible, transport object to lab or lift with tape if object can’t be moved

FIREARMS AND AMMUNITION

• Guns are used in the commission of many criminal activities
• Analysis of guns, bullets, cartridges, gunpowder/ primer residue, and shotgun shells/casings can be used to help solve crimes
• This is because gun barrels and firing mechanisms have specific properties that leave unique, identifying marks on the ammunition

TYPES OF FIREARMS

• Handguns (revolver, pistol)
• Long guns (rifles, shotguns, submachine guns)
• Machine guns

FIREARM BARRELS

Many barrels of guns are “rifled” – means that they contain grooves that help guide a bullet’s trajectory (can be oriented to the right or left)

TYPES OF AMMUNITION

• A shotgun shoots beads called “shot” and usually isn’t rifled
• Cartridges contain the bullet, gunpowder, case, and primer

BULLET AND CARTRIDGE COMPARISONS

• Rifling of a barrel creates marks on bullets (shotguns have smooth barrels)
• Class characteristics of bullet markings –manufacturer has certain number of grooves cut into the barrel of a particular type of gun
• Individual characteristics –imperfections in the rifling of a particular gun barrel or impression made by firing pin on a cartridge
• Must compare to a test fired bullet
• Class characteristics (lands, grooves, direction) to determine if same type of gun
• Use comparison microscope to line up striations on two bullets – find individual characteristics
• Perfect match over entire bullet is rare

AUTOMATED FIREARMS SEARCH SYSTEMS

• Integration of FBI and ATF computerized databases of firearm information = National Integrated Ballistics Information Network (NIBIN)
• Information is collected on bullets and cartridges cases

GUNPOWDER RESIDUE

• Unburned gunpowder is distributed when a bullet leaves the barrel of a gun
• Amount of powder present can tell distance between gun and object with powder residue
• Examine gunpowder residue on victim, victim’s clothing
• Test firings will help the examiner determine the distance from gun to victim

• Gunpowder from cartridge and primer residue may be found on person firing a gun in addition to the target/victim
• Test inside web of thumb and forefinger for residue