Terms in this set (492)
the science of associating people , places, and things involved in criminal activities
What does the work "forensic" mean?
latin for forum for public; as applied to public or legal concerns
Name four disciplines within the forensic sciences
What are two kinds of forensic science labs
Public - law enforcement
What is the main difference between those two types of forensic labs?
Usually public labs will only provide services to law enforcement or government agencies
Name three federal agencies that have forensic science labs
Department of Justice
Department of Treasury
Department of Homeland Security
Chain of Custody
The documentation of the location of evidence from the time it is obtained until it is presented in court
Who accredits forensic science labs?
Technical working group on education and training in Forensic Science
Forensic Science education Program Accreditation Commission
American society of Crime Laboratory Directors
American society of Crime Laboratory Directors- Laboratory Accredidation board
To whom are forensic labs accountable?
no mandatory accreditation
What is a forensic anthropologist?
identifying people who cannot be identified through soft tissue features, usually skeletal remains
French criminalist who developed a method of recording physical features of a person in such a way that the record would be unique to that person
What lab analyzes wildlife samples in criminal cases?
Teh US fish and wildlife service
Why would the Department of Defense need forensic labs?
To analyze military cases
What is a forensic toxicologist? How would this differ from a regular toxicologist?
Usually forensic toxicologist deals with blood alcohol levels and usually works hand in hand with pathologists
What is a crime scene?
Where everything starts and is the foundation upon which all forensic analyses are based, where a criminal act has taken place
What should the first officer or CSI at the crime scene do?
Detain any potential suspects
Render medical aid
Prevent others from doing the same
Name four safety issues for CSIs
Chemical and biological threats,
Is it ok to onlu take photos or only draw sketches? Why not?
No, photos give persecptive and sketches gives measurements
How many photos should you take at a crime scene?
As many as needed to get overall, intermidiate and closeups with and without numbers
Name three agencies that regulate worker safety
OSHA, Center for Disease control, National institure for occupational safety and health (NIOSH)
What is datum?
A fixed reference point where all measurements will be referenced back to
What is provenience?
Origin and derivation of an item in three-dimensional space in relation to a datum and other evidence
When is it acceptable to release a crime scene?
After the final survey
Material Safety Data Sheets
Who should be involved in the final walk-through of a crime scene?
CSI, Detective, two people from different agencies if possible
What should be included in a crime scene sketch?
Case identifier; Date, time, location; Weather and lighting conditions; identity and assignments of personnel;dimensions of rooms, furniture, doors and windows; Distances between objects, persons, bodies, entrances, and exits; an arrow pointing toward magnetic north
Should you take photos with of without a scale?
What does "BBP" stand for?
Blood borne pathogen
What does the Ramirez case teach us about safety?
Better off safe than sorry, precautions first and foremost
Judge and jury; whoever determines guilt or innocence
as information wherher in thr form of personal testimony the language of documents or the productin of material objects, that is given in a legal investigation to make a fact or proposition more or less likely
name four kinds of evidence
Circumstantial evidencePrima facie evidenceIncriminating evidenceFoundational evidence
What is exculpatory evidence?
Evidence tending to establish a criminal defendants innocence
What is "proxy data"?
the remnants of data of the events left behind
How is direct transfer different from indirect transfer? Give an example.
Direct transfer is evidence that goes from a source to a location with no intermediaries; indirect transfer involves one or more intermediate
What is persistence in relation to evidence?
Once evidence is transfered it will persist in that location until it further transfers, degrades until it its unusable , unrecognizable or is collected as evidence.
Is contamination evidence? Why or why not?
yes, undesired transfer of information between items of evidence. locard principle
What is class-level evidence?
group of items with similiar characteristics,
examination of the chemicaql and physical properties of an object and using them to categorize the object as a member of a group
Stating that two objects share a class identity
If you have individualized two pieces of evidence, how many common sources could they have come from?
one common source
What is the difference between questioned and known evidence?
Original source of evidence is unknown for questioned evidence and known evidence is knowing where the evidence orginated
What is a control? How is it difference from known evidence?
materials whose source is known and which are used for comparison with unknown evidence
What is the probative value of an item of evidence?
its value in proving or disproving the hypothesis
What is the difference between a type I and a type II error?
Type 1 an innocent party is incriminated and type II a quilty party is exonerated
What are the two hallmarks of science?
Testability and repeatability
What is a cross-transfer?
Evidence such as blood, fibers, that is transfer from suspect to scene or scene to suspect
Name three ways an association between a questioned and known item can be strengthened.
Kind of evidenceLocation of evidenceNumber of different kinds of evidence associated to one or more sources
Name three ways an association between a questioned and a known item be weakened.
Amount of evidencetransfer and cross-transferLocation of evidence
What is a simple magnification system? How is it different from a compound magnification system?
A magnifing glass, a single lens used to form an enlarged image, a compound uses 2 lenses
What is a virtual image?
The image the eye percieves, a result of a compoun magnification system.
what is focal length?
Distance between the two points of focus on either side of the lens
What is resolution?
Minimum distance two objects can be seperated and still be seen as two objects
Why is resolution more important than magnification?
it is the resolving power and if the points are below the resolving power you wouldnt see two objects , above and no more magnification will be benificial
What are the main parts of a microscope?
Eyepiece (ocular)Objective Stage CondenserIlluminator
If you saw "10X/0.54/170/0.17" on a objective, what would it mean?
Magnification of 10/ 0.54 is the aperature/ 170 is the tube length/ and 0.17" is reccomended thickness of cover slip
What is astigmatism?
where rays that propagate in two perpendicular planes have different foci
What does a condensing lens do?
Focus or condense the light onto the speimen field of vie
what is the difference between a real image and a virtual image?
the real image is the image on the screen and virtual is an enlarged or altered image
What is the refractive index of air? Of water? of a diamond?
"Angle in, angle out" is a shorthand way of characterizing what principle in microscopy?
What is a mounting medium?
material used to adfix samples to be viewed must have a ri close to that of sample
Name three material that are isotropic-besides air.
what does a polarizing filter do?
only allows the light to pass through that vibrates in that preferred direction.
Why do crossed polarizing filters create a black field of view?
They dont allow light to flow through at right angles, analyzer is inserted with orientation opposite that of the analyzer
What is birefringence?
double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials
A fluorescing substance contains...
What materials can be accurately analyzed by microscopy?
what is a wavelength? What unit of measure does it have?
Distance between any two waves; cm
Define frequency? What are the units? What is a wavenumber?
number of waves that pass a given point in one second;Hz; the inverse of wavelength in cm
How is the relationship between wavelength and frequency expressed?
speed of light (c) = wavelength (gama) x frequency (v)
How is the relationship between the energy of a photon and its frequency expressed?
E = hv
Rank the following regions of the electromagnetic spectrum in order of decreasing energy (list the highest energy 1st)
What happens to the molecules of a substance when x-rays strike it? Why are x-rays called "ionizing readiation"?
xrays pass through most matter but reflects off dense material
Why is the visible light spectroscopy always measured at the same time as UV light spectroscopy? What happens to molecules when light in these regions strikes them?
what happens to molecules when light in the infrared region strikes them?
Bonds start to vibrate
What is the most common type of detector used in UV/Visible spectrophotometry?
What type of light interactions with molecules is said to be quantized. What does this mean?
valence electrons absorb light and get promoted to higher energy level. the atom or molecule can onlyabsorb the exact amount or quatum of energy that corresponds
What does the unit "Hertz" measure?
What is a monochromator? How is it used in spectroscopy?
it is a prism or grating that is rotated thus exposing the sample to steadily increasing or decreasing wavelengths of light throughout the entire spectrum.selects wavelengths to expose to the sample
If you had two fibers that appeared to be the same color to the naked eye, what spectroscopic technique would you use to determine if they were?
UV Vis spectroscopy
Briefly describe the purpose of the Michaelson Interferometer in FTIR.
mathematecal concept that takes the beam splits it into two using a moving and a stationary mirror then recombing beam to hit sample takeing wavelengths the whole time and recalculates information, quick scans
What is diffuse reflectance? On what types of samples is it used?
IR techniques that uses an apparatus that caused the ir source light to counce off the surface of the material which then absorbs some of the light. opaque samples.
What is a diamond cell? When is it used?
diamond chips that a small amount of sample is placed that can transmitt light , when only small amount is available
What spectroscopic technique would you use to identify a pure sample of illicit drug?
All spectrphotometric detectors measure the amound of light that passes through a sample (or reflects off its surface). How can you determine what light is absorbed by the sample?
by using an instrument that measures absorbance. which consists of source, sample holder, way of breaking light into wavelengths and detector
what is normal phase chromatography? What types of substances are best seporated this way?
mobile phase is less polar than the stationary phase, drugs
What does the term "stationary phase" mean? What types of stationary phases are used in gas chromatography?
a finely divided solid material or a viscous loiquid that is containe within a long column,
What type of substance is the mobile phase in gas chromatography?
List two advantages of HPLC over GC.
can do reverse phase easily
composition of the mobile phase can be altered during the run (gradient chromatography)
Explain how a flame ionization detector works. What other types of detectors are used in gas chromatography?
A small flame that causes the sample to ionixe of lose an electron, which causes a current to flow.
What is reverse phase liquid chromatography? What types of substances are best separated using this technique?
The mobile phase is more polar than the stationary phase, non-polar substances, substances sensitive to high temps and large molecules
In HPLC, why would you want to use two pumps for the mobile phase?
to do a gradient chromatography, using two or more solvents
List and describe three types of detectors used in HPLC.
Diode array detector (DAD)
Describe three advantages of thin layer chromatography over other types.
No instrument is required
Many samples can be run simultaneously
Give at least two advantages of HPLC over TLC
Quantitative analysis easly performed
more sensitive and visible peaks on chart
What are the two general requirments for an analyte in order for it to be separated by GC?
In electrophoresis, what are the stationary phase and moble phase?
slab of a gel material such as agarose or polyacrylamide
An electric current
What is the major advantage of electrophoresis over other types of chromatography?
Define pH. Why is it important in liquid extractions?
Measure of acidity or alkalinity relative to water
How do extractions differ from chromatography?
it relies on adsorption not partitioning or competition
What is the difference between liquid phase extraction and sold phase extraction?
the liquid phase is two liquids competing for analyte whereas the solid phase is a solvent and a solid absorbent surface
What is the difference between adsorption and partition chromatography
adsorption the analyte is attracted to the surface of an absorbing material whereas partitin chromatography is seperation of analytes being distrubited between two solvents according to certain chemical properties (polarity and ph)
Why can HPLC be used for quantitation but TLC cant
Tlc is less sensitive and needs a means of visualization
How are the spots obtrained from TLC visualized
UV light, fluoresce, spots will show up as dark spots, add reagents that will color spots
How does capillary electrophoresis differ from gel electrophoresis
Gel is similiar to TLC whereas capillary similar to HPLC.
difference between cause and manner of death
cause of death explains the cessation of life and manner of deathe is the way in which cause of death came to be
what is the primary cause of death
three link causal chain that explains the cessation of life starting with the most recent condition going backward
Name the four manners of death
What is the difference between medical examiner and coroner
Medical examiner is usually a physician and usually appointed; coroner usually no formal education and appointed or elected
settling of blood due to gravity after the heart no longer circulates ( post mortem lividity)
Postmortem cooling another name
How long does rigor mortis last
Two to three days
Petechiae? where do they appear
pinpoint hemorhages found around the eyes and lining of the mouth and throat
Who was Milton Helpern
First head of medical examiners office in US in 1915
the disintegration of the body by enzymes releasd by dying cells
How many stages are there to decomposition
Two; autolysis and putrefaction
the branch of biology that studies the microscopic structure of animal or plant tissues
the act of digging up something (especially a corpse) that has been buried
What is the difference between blunt and sharp force trauma
sharp force is usually with sharp instruments such as knives or axes whereas blunt is trauma caused by dull or non sharpened objects, bats,brick, etc.
unburned gunpowder penetrates skin and burns it
Where does the term sheriff come from
England from reif of the shire to shire's reif
What causes rigor mortis
stiffening of the body after death due to the membranes of muscle cells becoming more permeable to calcium ions
The disintegration of the body by the action of bacteria and microorganisms
How accurate is algor mortis
Very low due to many factors affecting it, such as ambient temp, clothing and air currents
primarily concerned with the identification and examination of human skeletal remains, which can be used to reveal the sex, approximate age, race, and the presence of skeletal injury of a subject.
How is forensic anthropology different from archaeology
forensic anthropology takes the study of humans to situations of modern legal or public concern wheras archaeology is the study of past human cultures
Datum; how is it used
Referencee point from which all measurements originate
How can you tell if something is bone
A thin section is taken and microscopically examined for cell morphology
What is a biological profile
Assessing the sex, age at death , racial affinity, height, and any other aspects that would describe the individual class level information
Name the two areas of the body that are the most accurate for estimating sex
Pelvis and skull
The end portion of the long bone; used to help estimate age
What is the last epiphysis to fuse
Where is the pubic symphysis located
Junction of the two pubic bones lying roughly 4"-5" below the navel
What is the fourth left rib used for in forensic anthropology
estimating age by the ossification of the sternal end of the fourth rib, in advanced adulthood at a predictable rate
What needs to be known about a person before his or her stature can be calculated
Sex and ancestry
Another term for bicuspid
dental health professionals who apply their skills to legal investigations
How many teeth do humans typically have
When does the first adult molar erupt
What are the two methods of identification for skeletal remains
Dental xrays, frontal sinus xrays
The study of what happens to an organism from the time it dies until the time it ends up in the laboratory
What are some differences between the pelvises of male and females
male's more robust and larger, sciatic notch narrow ; females broader and sciatic is wide
What bone is the most accurate for estimating height
Long bones; femur
Name three ways to estimate age
pelvic bones, the ribs, and continuous remodeling of bone's cellular structure
What is an insect? is it the same as an anthropod
a six legged, three segment body organisms, a class of anthropods
How many kinds of insect development and what r they
3- ametabolous metamorphosis
What is the protective outer covering on an insect called
exoskeleton made of chitin and protein
growth phase of an insect
Classification of living things
What are the categories, in order used to describe an organisms taxonomy
Kingdom, phylum, class, order, family, genus, species
A fly found in Hawaii
Dead loving or those associated with decomposition
What are the uses of forensic entomology
estimate time of death, location, drugs ingested, poisons and location of stolen goods.PMI postmortem interval ( time between location of insects and time of death)
what is the difference between insects that larvaposit and those that oviposit
oviposit insects lays eggs and larvaposit deposits larva
Name three factors that go into calculating a postmortem interval
What are the four kind of species that can be found on a dead body
predatory and parasitic species
How many waves of insect invasion are there on a dead body
feed on the carrion itself, ex. diptera, coleoptera
Larvae of necrophagous insects called...
Maggot mass effect
the temperature of the body under the mass of living feeding maggots
What is the role of insects in decomposition
vital role in recycling of animal carcasses and other decomposition, forensicly they colonize in a predictible pattern and the phazes can help draw conclusions
What goes into the calculation of a PMI
the ecological and faunal study , which insects or therir yound inhabit a dead body and in what sequence; temperature, type and amount of insects
How would a forensic entomology case in Montana differ from one in Fl
the tempurature would slow the decomposition process adn in differenct ways the drier air, different types of insects would be on the corpse
shedding their skin
study of bodily fluids left at a crime scene
the set of proteins coded in the genetic makeup of an individual, the genome
Difference between a presumptive and confirmatory test
presumptive - highly sensitive to but not specfic for a particular substance
confirmatory - test positive for the substance and only that substance
Name the components of blood
Plasma - 90 % water 10% - proteins and other compounds
erythrocytes - red blood cells
leukocytes - white blood cells
What are leukocytes and what do they do
white blood cells, active in the immune system, provide the body's defense system
class of antigens produced by allelic genes at a single locus and inherited independently of other genes
List three presumptive tests for blood
3-aminophthalhydrazide; reacts with hemoglobin with and oxidzer and luminescences is blood is present
What does the test precipitin determine
diffusion reaction test to determine human blood
What is the most common presumptive test for semen
Acid phosphatase (ap)
What does ELISA stand for
Enzyme linked immunosorbent assay - antigen-antibody method to determine prostate specific antigen (p30)
How long can motile sperm survive in the vagina
average 3 hours , ranging from 1-8
Name the presumptive test for saliva
What is the difference between a wipe and a swipe
wipe is created when an object moves through and preexisting stain, swipe is transfer of blood onto a target
Cast off stain
results of blood being flung or projected from a bloody object in motion or one that suddenly stops
How is point of orgin determined
path of bloodstain (directionality) is determined and a string is run backwards and repeated for numerous stains until several converge
Is there a presumptive test for urine
Can through the presence of urea or creatine (picric acid)
What is angle of impact
Acute angle created by the intercept of the target witht the droplets' vector
What is the difference between forward and backward spatter
forward spatter is the the projection of blood away from the item creating the pattern
backward spatter is the projection of blood towards the item creating the pattern
What is acid phosphatase
enzyme in nature that occures at a very high level in semen
What are the four bases that make up human DNA
what is a gene
sections in the DNA strand which provides the chemical instruction to manufacture particular proteins in teh body
What is an allele
another name for gene or genic locus
List three ways that mitochondrial DNA differs from genomic DNA
located in mitocondria in the cell outside the nuclei
less mtDNA, more copies
comes from materinal side only
What is a restriction enzyme? What kind of DNA typing is ti used
endonucleases designed to cut DNA at a specific sequence of bases, RFLP
What are some of the advantages of DNA typing over other methods for identifying a person such as fingerprints
can determine lineage, male or female,
What does PCR stand for and what purpose was it deveolped
Polymerase chain reaction; to amplife DNA from insufficient or too badley degraded for analysis
What is STR? Why has it become the method of choice for forensic DNA typing
Short tandem repeat-most powerful has elevated dna from class to individual evidence
What is the impotance of amelogenin
locus on chromosome that determines sex
What is polymarker, how is it typed
gene that exhibits sequence polymorphisms; reverse dot blot
In RFLP what are the two ways that the VNTRs can be visualized
radio labeld dna and xrays
What is reverse dot blot? how is it used in DNA typing
method to type polymarkers, identifying the particular alleles present by reacting them with color-forming reagents on specially treated nylon strips
Which DNA method has the potential of generqating aprofile that can be considered to be unique, how?
What types of electrophoresis are used for the separation of DNA fragments in STR analysis
Taq polymerase, how is it used in typing
a polymerase enzyme used in PCR to amplify DNA which is stable at high temperatures and permitt the process to be automated using a thermal cycler
What is length polymorphism, example
DNA sequence that varys by the number of 1 repeat of a base pairs
what is sequence polymorphism , example
the sequences are the same except in 1 base
Heterozygous mean in DNA
if a person has different forms of the same gene, ex. blond and brown hair
What types of hairs do animals have
only mammals have hair
what are the growth stages of hairs
How can you tell if a hair may have been forcibly removed
if the root is stretched and has follicular tissue attached
What are some of the differences between human and animal hair
three types of hair: guard hair (large stiff Hair), fur hair (thinner softer), vibrissa (whiskers)
color banded hairs,
What characteristics are used to determine body areas
diameter, shaft ( buckling, shouldering, wavy, curly, arc), tip
Why is estimating ancestry from hairs difficult
accuracy is low, humans are more variable from on to another in their hair morphology than any other primate
Name three ways in which a hair can be cosmetically treated
What constitutes a suitable known hair sample
50-100 hairs from all portions of the area of interest, typically the head/scalp or pubic area. combed and pulled hairs must be collected, must be representative of the collection area.
What is a comparison microscope
is composed of two transmitted light microscopes joined by an optical bridge to produce a split image
What are the three conclusion that can be drawn from a microscopical examination of hairs
1)same microscopic characteristics as the known hair sample, then it could have come from the same person who provided the known sample
2) similarities but slight differences to the known hair sample, then no conclusion can be drawn as to whether the questioned hair could have come from the known source
3)exhibits different microscopic characteristics from the knwon hair sample, then did not come from known source.
how does the use of mtDNA assist in hair comparisions
help distinguish between hairs from different sources although they have similiar but insufficient microscopical hair characteristics
How would you distinquish between males and females using hair
sex cannot be determined by hair
Can you tell how old someone is by lookin at his or her hair
What are cortical fusi
small bubbles found in the cortex
What are the three macroscopic parts of a hair
Color ( white, blond, brn etc), Hair, diameter, length
What are the three microscopic parts of a hair
Color (natural, treated), Pigmentation, Structure
How would you distinquish between a head hair and pubic hair
Head is usually straight, curly, may be very long, diameter is even
Pubic has buckling, extreme waviness, diameter varies
Can you use statistics to describe the significance of hair comparisions
How could you tell if a hair is really a synthetic fiber from a wig, what would you look for
fibers and hairs have different microscopic characteristics
What is a synthetic drug? name one
A man made drug; BZP
What are the two major criteria for deciding if a drug shall be put ina Federal Schedule
physical addiction, medical uses
When will a drug be put in Schedule I
has a high potential abuse and dependence; no medical uses
What schedule would drugs that require a doctors prescription and which are not listed in another Schedule be put in
What is speed? What family of substances does it belong to? Where is it scheduled
Amphetamine, Stimulant; II
What was the first act passed by Congress to control drugs?What were its main provisions
1906 Pure food and drugs Act; prohibited interstate commerce in mislabeled or adulterated food or drugs
What was the Harrison Act, its purpose, what drugs was it aimed at
to provide the registration with collectors of irs and to impose a special tax upon all persons who produce, import manufacture, compound deal in dispense or give away opium, or coca leaves thier salts /derivativites
What is the signifigance of Usable quantity in drug control? example
An amount of drug that is likely to have a demonstrable psychoactive effect on an average person. Mere traces not enough to prosecute. ex. 0.02 heroin
What is an excipient , its purpose
Substances that may mimic the activity of the main illicit drug present in order to make it more difficult for the user to known just how much of the drug there really is in the exhibit
diluent, why r they used
chemicals that are used to dilute an illicit drug to give it more bulk, cuts purity increases profits
Aggregate weight in regards to drugs
The weight of the drug and any cutting agents present
Spot or field test, drug or class, when used
Marquis, Heroin (opium derviatives), screening or field test
What type of test is used to detemine the percentage or quantity of a drug in a mixture
Confirmatory test ( GC/MS)
What tests are used for confirmation of drugs
What are the differences of marijuana analysis compared to other drugs
Can be confirmed with microscopy and color test, no instrumental analysis required
Both FTIR and mass spectrometry are used for confirmation, when would it be appropriate to use one or the other
If pure the FTIR if seperation is needed Mass spec
LSD is considered unique in the family of illicit drugs why? how does its occurrence differ from other drugs
Absorable through the skin, it is poured onto blotter paper
The science that studies the relationships between drugs and living things
Pharmacology different from toxicology how
toxicology is a portion of pharmacology that harmful effects of drugs on humans
What role does forensic toxicology have in deteming cause and manner fo death
They work with the pathologists to help determine the cause and manner of death
What is major type of cases handled by toxicologist?
dui's- where subjects have taken drugs and not died
What makes case unique for toxicologist
must determine amount of alcohol in system and how it would have affected the drivers ability behind the wheel
Metabolism as it applies to toxicology
a process whereby a drug or other substans is chemically changed to a different form
What role does the liver play in metabolism
Most metabolism takes place in liver where enzymes cause chemical changes
What is the science that describes the fate of drugs in the body from the time they are taken until eliminated
What factors can affect the rate at which alcohol is absorbed from the stomach into the blood stream
Nature of the drink, rate and speed of drinking, contents of the stomach at the time of drinking
What are the major routes of elimination of drugs from the body
Excretion in urine, respiration, persiration
For alcohol what is the most important route of elimination from the body
a continuum of physical and psychological attachments related to the concept of behavioral addiction
Phenomenon where by the body's organ systems adapt to the drug
Difference between dependance and tolerance
What tests are commonly used for confirmation of a drug in the body
What are immunoassay test , when are they used and what are the two major types
reaction between antigens and antibodies; EMIT (enzyme multiplied immunassay test)
What is cut-off levels, why does tox labs use them
A limit of detection; a level below which a reliable result cannot be detemined. so noise would not be mistaken for a signal
when is blood not the best source for tox, blood generaly best why
Preferred medium for blood alcohol measurement, best surragate for brain alcohol levels. Not best if theres been a transfusion
Blood alcohol concentration is plotted against elapsed time
Widmark curve straight-line slope measures what
The absorption rate of the BAC. equal to the rate of metabolism in the liver
What is the principle of operation of the Breathalyzer
Measures the number of grams of alcohol in 210 liters of deep alveolar (lung ) air. diffusion of oxygen and carbon dioxide are exhanged between the blood and sir throough the alveolar, therefor if there is alcohol in blood it too is eliminated through alveolar
What type of instruments are used for measuring blood alcohol
preliminary breath testing instruments (PBTs) and those that are accepted for evidentiary purposes.
Horizontal gaze nystagmus , when is it used
The jerky movement of the eyes if under the influence of alcohol when looking at a moving object
What is a fiber
a unit of matter, either natural or manufactured that form the basic element of fabrics and other textiles and has a length at lease 100 times its diameter
Continuous strands of textile fibers, filaments or material in a form suitable for weaving, knitting, or otherwise entangling to form a testile fabric
how is yarn different from thread
Thread refers to the product used to join pieces of fabric together, typically by sewing; yarn is the product to make fabric
How are woven and knitted fabrics different
Fabrics composed of two sets of yarns, called warp and weft and formed by interlacing of these sets of yarns.
Knitted- constructed of interlocking series of loops of one or more yarns and fall into two major categories warp knitting and weft knitting
various families of fibers produced from fiber-forming substances which may be syntesized polymers, modified or transformed natural polymers or glass
manufactured fibers that are synthesized from chemical compounds (nylon, polyester)
dry twist test used for what
shower head-like device used with spinning
What is the fiber-forming substance called before it is spun into fibers
Linear measurements based on weight per unit length
Manufactured fibers with diameters from about 6um up to a size limited only by the width of the spinneret holes
Fibers vary in shape but always thicker in center so they act as lenses and disperses the light that passes through them
How is becke line used to determine it
When observing the fiber, if the working distance is increased ( stage moved down) , the fiber has a higher RI if the becke line moves toward the fiber; if the mounting medium has a higher RI the becke line moves towards the medium
Why are fibers birefringent
interference colors seen after crossing the polarizing filters material nature, orientation, and crystallinity
those that appear to match in one set of lighting conditions, but not in another
Why is the cross-sectional shap of the fiber important
shapes vary for manufactured fibers and vary with the desired end result, may be indicative of fibers end use and the measurement of the diameter is dependent on the shap
Finely ground particles of materials such as titanium dioxide that are introduced into the spinning dope,
how is delustrant used
help diffract light passing through the fibers and reduce their luster
How many cross-section shapes are used in making manufactured fibers
How many commercial dyes available
how many colors can be produced in textiles
Instrument that allows for the color measurement of individual fibers. essentially a standard spectrophotometer with a microscope attached
Difference between paint and coating
one is a covering of any kind the other is a suspension of pigments and additives intended to color or protect a surface which is a coating
portion of the coating, other than the pigment, which allows the pigment to be distributed across the surface
What are the categories of coatings
Architectural, Product coatings, special-purpose coatings, art paints
A clear solution of oils and organic or synthetic resins in an organic solvent
Second coating usually an epoxy resin with corrosion-resistant pigment
Unpigmented coatings applied to improve gloss and durability of a vehicile's coating
How should paint be collected if it is fragile or fragmentary
very carefully, photographed then take whole item if possible, removed with non-metallic tools
A mini-vice that holds a sample in place while a heavy and very sharp glass or diamond-edged knife slices off secttions a few tens of microns thick
What is the problem with solubility testing of paints
What types of instrumetation are routinely used to analyze paints
PLM, IR, Pyrolysis-gas chromatography, PGC-MS, Absorption spectroscopy (MSP), SEM/EDS
What is a color system, name two
gross visual color of paints, Munsell system adn the Commission International de l'Eclairage (CIE)
What facters strengthen an association between two indistinguishable paints
Number of layers, sequence of layers, color of each layer, cross-transfer of paint between items
Paint Data Query: run by RCMP database of layer structures, primer colors, binders, pigment chemistry, and topcoat chemistry in both visual and spectrometric
What does a solvent due in regards to paint application
Dissolves the binder and give the paint a suitable consistency for application
Are physical matches possible with paint chips
yes but very difficult
What is batch lot
A unit of production and sampling that contains a set of analytically indistinqishable products.
definition depends on who is working with it: as earth material, either natural or manmade (concrete, gravel) that is transferred from a crime scene to a person or object or vice versa
Major componentents of soil
Organic and inorganic materials; decayed and vegatation, animal matter, grass, insects, (humus), crushed rock and clay materials. minerals
study of transfer of soli particles from such locations to objects such as car and clothingeither accidentally or purposefully.
Where does humus come from
organic material of soil, decaying vegitation, animal matter, insect, animal droppings
How is glass defined
What properties does glass have that are like those of a solid? liquid
it is hard, but can be fluid when hot
what is refractive index and its units
ratio of the velocity of light in a vacuum (or air) to the velocity as it passes through the medium
glass: hard, brittle material that is usually transparent, but which lacks the ordered arrangement of atoms that is found in most solids
manufactured by melting sand and the other desired ingredients and then allowing it to cool without crystallizing. flat glass such as used in windows
strengthened glass by heating and cooling rapidly producing deliberate stress in the surface
cracks formed on the side opposite the side of the impact, radiate out in all directions from the point of impact
how do radial cracks determine direction of impact of an object on glass
They form on the opposite side of impact; forming right angle at the point of impact
circular cracks formed on the side of impact
a system in which particles are dispersed in a continuous phase of a different composition (or state).
how are dispersion curves constructed
repeating the Becke line experiment at different wavelengths and ploting wavelengths vs RI
If a piece of glass is immersed in a liquid and a becke line is seen under a microscope, how can you tell which has the higher refractive index
Move the objective closer and whichever the becke line moves closer to has the higher RI
Ri and temperature
Inversely proportionaly to temperature;as temp raises RI decreases
Ri and incident light
Inversely proportionaly to wavelength:
under what condition can a piece of glass be individualized to a particular source
When they can be pieced together like a jigsaw puzzel
how can you tell if a headlight were on or off at the time it was broken
If there is formation of oxides on the surface of the filament then it was on at time of impact, if light is off there will be no oxides seen
Depicts the elements that must be present in order to have a fire: source of heat or energy, fuel, oxygen, chain reaction
where oxygen atoms combine with hydrogen and carbon to form water and carbon dioxide; fire
or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species
how do fire extinquishers work in general
deprives fire of oxygen
A chemical reaction that releases energy
Lowest temperature that will allow a liquid to produce a flammable vapor
Fuels that are easily vaporized and support combustion and are highly exothermic
Types of fires
Natural, accidental, deliberate (incendiary)
In order to determine that a fire was arson what must the fire investigator be able to do
All possible natural and accidental causes of the fire must be eliminated.
Why is finding the point of orgin of a fire so important in determining the cause of fire
This is where the initial ignition took place, if accelerants were used most likely at this point.
Difference between fire and explosion
Speed of reaction, rate of combustion is higher for explosion, and explosions can occur withoiut confining fuel
supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it
why do some explosives detonate whereas others do not
some explosives are combine the oxygen and fuel into a single molecule which undergoes instante combustion
Initiating explosive / non-initiating explosive
Type of high explosive: initiating high explosives are usually very powerful and very sensitive, usually used to detonate less sensitive explosives; non-initiating are not that sensitive usually takes a good deal to detonate
Using one explosive to set of another; series of explosions which take place in a particular order
Difference between high explosive and a high order explosive
high order describes the effiency of a particular explosion not the type of explosive
What characteristics of fuel and oxygen give rise to a high explosive
fuel and oxygen are chemically combined creating a higher rate of explosion
detonation velocities below 3,200fps, low explosive usually used as propellants
how is explosive residues collected
where is the most important place to look for explosive residues
At the seat of the explosion
color test for nitrates, coloring bright red. most explosives have nitrogen
Italian physian in the late 1800's theory of l'umo delinquente, the criminal man, criminals could be identified by unattractive characteristics , their external features reflecting their internal aberrations
Alphonse Bertillion called his complex system of anthropometric measurements, photographs and a detailed description
When wa the first systematic use of fingerprints in the US
in 1902 in New York City
Criminal Justice Information Services Division - national repository and clearing house for all fingerprints
Why are friction ridges important
they are permanent and fixed in their patterns and stay throughout life
Four methods of visualizing latent prints
powders, photography, chemical, and visual (ALS)
How are lasers used with latent prints
Latent prints have natural flouresence, uses different wavelengths, can also use flouresent powders
various ridge characteristics
What is a point counting standard
dictates how many points of comparison were required before a positive conclusion could be reached
name the types of fingerprint patterns
Loops, Arches, Whorls
Automated Fingerprint Identification System
Level 1 detail
general ridge flow and pattern configuration
Level 2 detail
includes formations, defined as a ridge endings, bifurcations, dots or combinations of these features, which inables individualization
Level 3 detail
includes all attributes of a ridge, such as ridge path deviation, width, shap, pores, edge contour, incipient ridges, breaks, creases, scars,a dn other permanent minutiae
What are elimination prints
Known samples of fingerprint of subjects
Why is it more difficult to distinquish handwriting among a group of third graders than among adults
because they are told to copy the examplar precisley and are learning so take very good care, then as they grow the need to concentrate so hard lessens and the writing habits become internalized and subconsious then individual charateristics develop
Precautions needed when collecting handwriting samples
suffient amount of writing to ensure that a normal variations present; each sample on new piece of paper; writings should be collected by dictation
Major characteristics of forged handwriting
spacing between letters, individual letter formations, formationsof letter combinations
Give an example of a handwritten questioned document that is not written on paper
computer screen, blood on wall,
What characteristics of ink are most usefull for comparing known samples with unknowns
chemical analysis, age of ink
how can chemical erasures be detected on a document
by the different shades of color of the paper from bleaching and chemicals in UV or IR light
mechanical erasures be detected on a document
By the disturbance of paper coating and fibers at the point of the erasure with a low power microscope
What are some of the ways you can detected a zero added to a check
age of ink compared to rest of document, chemical composition of ink
How should requested writing be taken if the entire questioned document is a check
have suspect write a check out
any material that the authenticity is questioned
the age of the ink on the document, done by observing its behavior as it dries. Can do this by redisolving in suitable solvent
How many points of identification are necessary for a questioned document examiner to be able to declare that a questioned document was written by a particular person
no minimum set number can depend on size of document
difference between requested writings and non-requested writings
one is dictated writings from a someone and the other is normal day to day writings of someone
Electrostatic Detection Apparatus
What is ESDA used for in document exams
Capturing indented writings
best way to decipher indented writings
A document that was burned but extinquised before completely destroyed.
how can you decipher charred documents
Strengthen by misting them with a lacquer or alcohol or water. then can treat like obliterations. use UV or IR
Why is questioned document examiner considered an apprenticeship field
No formal training available so training is done as apprenticeships
Difference between pistol and revolver
revolver feeds ammunition into the firing chamber by means of a revolving cylinder whereas a pistol feeds ammunition by a spring-loaded vertical magazine
four differences between rifles and shotguns
shotguns shot round pellets or slugs, no rifling and have a limited effective firing range, doesnt shot bullets
Why is a pistol not a rifle
rifles are shoulder weapons and the cartridge must be expended manually
a material in the shotgun pellet shot that is placed between the powder and pellets to maintain even pressure on pellets and pushes them out all at once
diameter of a shotgun barrel
how do you determine caliber
refers to the size of the ammunition cartridge, used to mean the bore diameter
name the parts of a cartridge
casing, primer, a propellant, solid projectile
what does a primer do
Ignites the propellant, small metal cup containing a percussion-sensitive material
Raised portion of the barrel between the grooves, digs into the bullet surface as it travels down the barrel imparting a spin to stabilize the bullets flight
The indented portion of the rifling of a barrel to impart spin to a bullet as it leaves the barrel
what material are used to estimate muzzle to target distance
cloud of molten metals, parially burned gun powder flakes, smoke and other microscopic debris discharged from a firearm when fired
do striation appear only on bullets, why why not
Shotgun do not have rifling
are more firearms involved in homicides or suicidies
suicides ~ 57%
What determination can be made from a gsr analysis
subject was near or around a weapon that was fired, or held a recently fired firearm, fired a weapon
how are bullets compared
by the striations on the bullets of the questioned bullet and a known bullet fired from the questioned gun
how are serial numbers restored
by applying an etching chemical on the obliterated area
What is sodium rhodizonate used for
chemical treatment to a surface to check for GSR; spray with chemical then treat with series of acid sprays; pink and or purplish blue appearance means presence of GSR
Residue of lead, primer materials, carbon, and other materials from the barrel that are transferred onto the outermost surface of the target by the bullet as it passes through
donor object or a material is pressed against a recipient object or material and some force is applied the donor may leave an impression in the recipient
What are the difference between two-dimensional and three- dimensional evidence
2D is an impression left on a surface from depositing material; mud from shoe on floor
3D is an impression left in a surface. impression of shoe in mud ( can cast)
Under what conditions can impression evidence be individualized
Must have sufficient unique characteristics present in the impression
how are imprints lifted
powder then tape, gel tapes, electrostatic lifting devices
how are 3 dimensional impressions lifted
Casting material; dental stone
How are casts made of impressions
make a form around the impression, pour dental stone into the form wait till it hardens then lift
how many characteristics are necessary in order to individualized a footwear or tire impression
no set number, each case is determined on its own uniqueness
major class characteristics present in footwear impressions
type of shoe, manufacturer, size, model
major individual characteristics present in footwear impressions
wear, walking gait
major diff between tire tread and footwear impressions
tire impressions can not be lifted and taken to the lab as in some footwear impressions
Tire tread stance
distance from the centerline of right tire to the centerline of left tire
Wheelbase on a car, how to measure
distance from the center of the front hub to the center of the rear hub;
What are major reasons tires have treads
increase friction and mninimize slippage, move water out of way
write an equation that shows how copper chloride reacts with iron
CuCl3 + Fe3
chemical bonds between atoms of metals
what is its (metal metal bonding) in serial number restoration.
the serial number is stamped into a metal the metal is compressed and the metal -metal bonding is disrupted and the metal structure is weakened
Can an obliterated embossed serial number be restored the same as stamped ones
possibly depending on the material
why can stamped serial numbers normally not be restored in plastic
very difficult they are polymers, very stable substances and are insoluble in solvents
Under what conditions would fingerprint evidence be considered impression evidence
When it is in an impressionable surface, paint, blood, putty
why are firearms and toolmarks considered to be impression evidence
two items come into contact with sufficient force, such that one or both of the items bear markings resulting from the other item
Should you answer a question with only yes or no
you ca can not be n but most generally answered accuratley with just yes or no
Someone who knows more about a topic or subject than the average person
Do you have to respond to a subpoena
yes, it is a court order demanding the presence of a withness at a specific time and place to give testimony or other evidence
a dress rehearsal; between witness and attorney to review all the significant aspects of the case and your testimony
what should be included in a report
Name of examiner, agency, date reported, case id, items examined, methods, results, statement of dispositon and signature
How do forensic science laboratory casework reports differ from scientific papers
It is not intended for other scientist but for law enforcement, judges, people with no training in sciences
3 things you should do when you testify
Review your paperwork and reports, allways tell the truth, do pretrial
4 things you shouldnt do when you testify
don't discuss the case with anyone, dont volunteer information, never get angry , dont guess
Why do some people describe all expert testimony as being opinion testimony
Expert testimony is the only one allowed to state opinions during testimony, due to thier expertize on the subject
trier of fact
Judge or jury
what parts of the fifth amendment affect evidence, how
Due process clause; protects against outrageous government behavior to collect evidence, ex. pumping someones stomach to get the illicit drugs
Jame frye, what was he accused of
what was the substance of the judges opinion of frye case
the standard for novel scientific or technical evidence that came out of this decision was that before a new scientific technique could be introduced in court the underlying principle that governed it must have achievd general acceptance within the particular scientific field from which it belongs
what is an expert and who decides if the witness is an expert,how
Someone who knows more about a topic or subject than the average person; the judge by taking the witness credentials (vior dier) and making the decision if he is qualified
what are difference between expert and lay witness
lay witness is usually first-hand observations and impressions whereas expert witness can offer opinions and lay witness can not
how is evidence defined
anything that will help prove or disprove a material fact
difference between indirect and direct evidence
an inference is required to connect it to a conclusion of fact. By contrast, direct evidence supports the truth of an assertion directly—i.e., without need for any additional evidence or the intervening inference.
French for speaking the truth; process in which a witness is asked questions of his credentials to become qualified as an expert witness
what parts of 4th ammendament affect evidence
unreasonable searches and seizures, protects objects property and personal papers and effects
eggs yield immature forms that look like smaller forms of adults. (without change)
hatchlings emerge in a from called a nymph resembles a wingless version of the adult ( gradual)
most complex; adult lays eggs or depostis a larva onto a food source, start eating then go through instars, look nothing like adult species.