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Forensic Science Test 2
Ch 7, 8, more
Terms in this set (132)
Deals with the examination and analysis of blood fluids, including saliva, semen, urine, and blood.
Properties of Blood
40 % blood volume loss (exsangunation) for death, which is 5-6 liters for males and 4-5 for females.
On average, account for 8% of total body weight
Red blood cells; responsible for oxygen distribution. MOST NUMEROUS. No nucleus-no DNA
White blood cells; responsible for "cleaning" the system of foreign invaders. LARGEST, LEAST NUMEROUS. Nucleus-DNA
Platelets; tiny; responsible for blood clotting SMALLEST
Fluid portion of the blood (55%)
ABO blood group
Based on having A, B, both or none of the factors on the red blood cell
May be present on the red blood cell; positive if present, negative if not
A substance that can stimulate the body to make antibodies. Certain of these (proteins) found in the plasma of the red blood cell's membrane account for blood type
A substance that reacts with an antigen
Clumping of red blood cells; will result if blood types with different antigens are mixed
discovered that there are 4 diff kinds of human blood based on the presence or absence of specific antigens found on the surface of the red blood cells.
Presumptive Tests for Blood Determination
Kastle-Meyer color test//Microcystalline tests//Leucomalachite test//Luminol test
Determining Human from Animal Blood
Microscopic survey: different cellular characteristics
Precipitin test- blood injected into rabbit, withdrawn and tested
Characteristic Differences: types and sizes of cells
(Frogs- larger nucleic red blood cells)
Universal Donor Blood Type
Universal Recipient Blood Type
Population Distribution of Blood Types in the U.S.
Dr. Leon Lattes
Invented a way to test for antibodies in dried blood flakes in 1932: Absorption-elution
Professor of Criminalistics, wrote book that contained a chapter in which he discussed the application of blood stain pattern analysis to criminal investigators. Instrumental in Sheppard's case based on blood stain pattern photos
Among the smallest and most highly specialized cells in the human body; head and tail, 23 chromosomes with the genetic material in the head
Determination of Seminal Fluid
Acid phosphatase color test, Prostate Specific Antigen
Victim to undergo medical examination asap, physical evidence like clothes, hairs, vaginal and rectal swabs must be collected and sent to lab. Bedding too
Physical Evidence from the victim
Swabs, hairs, blood sample, fingernails
Physical Evidence from the suspect
Male's underwear, pubic hair, head hair, penile swab, blood sample. Also maybe transfer of blood, semen, saliva, hairs, and fibers
80% of people are this. Their blood-type antigens are found in high concentration in their body fluids.
Blood Spatter Evidence
A field of forensic study which deals with the physical properties of blood and the patterns produced under diff conditions as a result of various forces being applied to the blood. It follows the laws of physics.
Questions Answered by Blood Spatter Interpretation
Distance between target surface and origin of blood/point of origin of the blood/movement and direction of a person or object/number of blows, etc/type and direction of impact that produced blood/position and movement of the victim during or after bloodshed
Blood Droplet Characteristics
-Will remain spherical in space until it drops onto a surface
- Once it impacts a surface, bloodstain is formed.
-Droplet falling from same height, hitting surface at same angle, will produce a stain with the same basic shape.
Blood Droplet Volume
.05 cc, range from.03cc to.15cc. Dependent upon the surface or orifice from which it originates. Impact area=target
Shape and Size of Bloodspot
Depends mostly on nature of target surface (texture, porous or nonporous). Size is related to distance fallen, lil change in spot diameter beyond a fall distance of 1.2m(7ft)
Target Surface Texture
Harder, less porous the surface-less drop breaks apart
Hard, smooth surface- little or not distortion around the edge
Pointed end of the blood stain
faces the direction the stain is traveling
When a bloody object comes into contact with a surface and leaves a patterned blood image on the surface.
Image is recognizable and may be identifiable with a particular object (knife on jeans, boot bloody footprint)
Wet blood is transferred to a surface which did not first have blood on it. (fade out towards end)
A non-blood bearing object moves through a wet bloodstain, altering the appearance of the original stain(blood already there, put your hair on it and move/change the blood stain)
Relates to the direction a drop of blood traveled in space from its point of origin
The greatest speed to which a free falling drop of blood can accelerate in air. It is dependent upon the acceleration of gravity and the friction of the air against the blood
Gunshot. (Back-spatter from entry wound, forward-spatter from exit wound); fine mist appearance
Person walking, free-falling drops, dripping, splashing, arterial spurting
Shape of a blood stain
Round- falls straight down at 90 degree angle
Elliptical- Blood droplet elongates as the angle decreases from 90 to 0
Formula: width/angle length=sine of the impact
More acute the angle, the more elongated the stain.
90 perfectly round, 80 takes on more elliptical shape.
30, produces tail.
Cast-off from Weapon
First blow causes bleeding. Subsequent blows contaminate weapon with blood, which is ___ tangentially to arc of upswing or backswing.
Depends on type of weapon, amount of blood adhering to weapon, length of arc
Point of Convergence
Location of the blood source can be determined by drawing lines from the various blood droplets to the point where they intersect.
Point of Origin
Where the "blow" occurs. 3D. Determined by drawing a line from area of intersection straight up to where the angle of impact would intersect.
Blood stain patterns are considered circumstantial. Not 100% exact, there are some things people can read into that others don't see. Still important if person doing the analysis has some credibility.
Herbert L MacDonelll
Father of modern bloodstain pattern analysis. 50 cases, OJ, Sen. Rob Kennedy and MLK Jr.
1985 isolated DNA markers and called them DNA fingerprints. Credited with the DNA profiling using RFLP.
1985 developed PCR testing, Nobel Prize winner.
James Watson and Francis Crick
1953 discovered the configuration of the DNA molecule
Arrested and his DNA profiled matched the semen from both murders in England. 1988 he was sentenced to life for the 2 murders.
Tommy Lee Andrews
1986- first trial to admit DNA in the U.S. Jeff Ashton was the prosecture, first one to prosecute a DNA case.
DNA evidence taken from his grave site was compared to 2 descendants of James' sister and found to match almost exactly.
Case where Beamish was convicted when a leather jacket was found with victim's blood and 27 strand of white cat hair. Beamish had this white cat
Hitchhiker killed, man denies it. But seeds in his car match only one tree.
Double helix, 2 coiled DNA strands. Composed of nucleotides- containing a sugar molecule (Deoxyribose), phosphate group, and a nitrogen containing group.
A to T and G to C
DNA Body Locations
Can be found in all body cells- blood, semen, saliva, urine, hair, teeth, bone, tissue. Most abundant in our buccal (cheek) cells
Blood mainly composed of red blood cells with no nuclei, therefore no DNA. DNA from white blood cells
23 pairs of chromosomes with one set coming from mom and one set coming from dad. First 22 are autosome, last pair are sex chromosomes
A method in which DNA is converted into a series of bands that ultimately distinguishes each individual
3% of human DNA sequences code for proteins. 97 is non-coding and repetitive. 50% of human genome has interspersed repetitive sequences.
Uses for DNA profiling
To identify potential suspects, to exonerate individuals, to identify crime and casualty victims, to establish paternity, to match organ donors.
Restriction Fragment Length Polymorphism. (Isolation, Cutting, Sorting, Analyzing)
Polymerase Chain Reaction- technique for making many copies of a defined segment of a DNA molecule.
Every gene has at least 2 of these, one from mom and one from dad.
Separating the strands of DNA by heating
Attaching the primers
Adding the dNTPs and duplicating the DNA
An electrical current moves through a substance causing molecules to sort by size. Smaller,lighter molecules move the furthest on the gel. (Run the gel, observe and compare bands of DNA)
Short Tandem Repeats, latest method of DNA typing. Locations (loci) not the chromosome that contains short sequences of 3 to 7 bases that repeat themselves with the DNA molecule.
Extract the gene from the sample. Amplify sample by means of PCR. Separate by electrophoresis. Examine the dissonance the STR migrates to determine the # of repeats. Continue process with other STRs from other genes.
Seperation of STR Fragments
Electrophoresis- Fragments separated on basis of mass/change. Gel or Capillary- cause the DNA molecules to move up through the machine
STR Detection Methods
Silver staining (gel only), Fluorescence detection. STR Genotypes visualized on electropherogram.
BC fast, abundant throughout genome, variable, small size,use of small amounts of DNA, inherited independently from mom and dad.
7, partner to profiler, first and last are repeats as double check.
16 total, used in St. Louis
3 Possible Outcomes
Match- DNA profile appears the same.
Exclusion- Genotype comparison shows profile differences that can only be explained by the 2 samples originating from different sources.
Inconclusive- The data does not support a conclusion as to whether the profiles match.
By increasing the # of alleles on different loci, the prob of having 2 people with the exact combination becomes astronomical.
Combined DNA Index System, used for linking serial crimes and unsolved cases with repeat offenders. Links all 50 states, requires >4 RFLP and/or 13 core STR markers
John M. Butler
THE leading expert on DNA Typing.
Found in the nucleus, constitutes 23 pairs of chromosome from both parents. Each cell only contains one nuclei.
Found in cytoplasm, inherited only from mother, Each cell contains hundreds of mitochondria. Can be found in skeletal remains. (rigorous, much time, costly, no database) Constructed in a circular pattern. Best used when nuclear DNA typing is not available.
Compared mtDNA of unknown soldier with Blassie's mom and sister and found a match.
Y- chromosome Analysis
Y chromosome is the only one without a partner. It is alone and recombines with itself. Most of the Y chromosome, passes almost unchanged from generation to generation.
Y chromosomes and mtDNA
Never lead to one individual, but narrowed down
Thomas Jefferson's property, did she have his child? Yes, genetic link between Jefferson and Hemings descendants. Could have been any male Jefferson, this was all run by STR.
Group of college law students work on cases where DNA may prove innocence (or guilt). Exornerate the wrongly convicted throughout post conviction DNA testing; and develop the implement reforms to prevent wrongful convictions. 318 exonerated
People working on Romanovs
Forensic Anthro- Anthony Falsetti
Medical Examiner- Baden
The level at which evidence provides proof of the crime.
Used to place a suspect at a crime.
How often something occurs in nature or the "real world".
Any small pieces of material, manmade or naturally occurring (animal, plant, or mineral). These include hair, fibers, glass, soil, sand, plant material.
Most frequently found pieces of evidence at the scene of a violent crime. Provide a link bet went the criminal and the act. Can determine: Human or animal, race, origin, manner in which hair is removed, treated hair, drugs
Part of the hair that sticks out of the skin
Lies below the epidermis
Structure from which the hair grows
Cuticle- outside covering, made up of overlapping scales
Cortex- outer layer made of keratin and imbedded with pigment; also contains air sacs called cortical fuss
Medulla- inside layer running downy the center of the cortex (Continuous, intermittent, fragmented, absent)
Hair cuticle- scales
ALL IMBRICATE ARE NOT HUMAN, ALL HUMAN ARE IMBRICATE
Measuring diameter of the medulla, dividing it by the diameter of the hair, for humans less than 1/3, animals greater than 1/2
depends on cross-section being round (straight) oval (curly) or crescent (kinky)
Hair Growth Terminology
Anagen- hair that is growing
Catagen- hair at rest
Telogen- hair that is dying, up to 2 to 6 months
1 half inch per month
Class characteristics of Hair
Color, length, diameter, distribution of pigments, scale types, absence or pre scene of medulla type pattern index
Control sample of hairs
50 from scalp, 24 pubic hairs
Age and sex cannot determined (sex can be if DNA analysis of root tissue is present). Hair root with follicular tissue can indicate if hair was pulled out forcibly
Hair individual characteristc
If DNA is available, from root. Everything is class, even mtDNA which can come from the shaft
Class evidence, probative value, common trace element, compare physical and chemical characteristics
Made of fibers and fibers are made of twisted filaments
Natural- animal, vegetable, or inorganic sources (silk, cotton, wool, cashmere)
Artificial- synthesized or created from altered natural sources (polyester, nylon, etc)
Testing for Identification Fibers
Microscopic observation- color and fiber surfaces
Burning- how fibers burn, the odor and appearance of residue
Thermal decomposition- gently heating to break down the fabric to their monomers
Chemical testing- solubility and decomposition
Density- mass of object divided by volume of object
Refractive Index- measuring the bending of a ray of light as it passes from air into solid/liquid
Flurosence- comparing fibers of common origin
Fourier Transform Infrared Analysis- based on absorption of wavelength of light
Fiber Individual Characteristics
Only 1 sources for the transfer material where contact took place, contamination of different materials from surface one to surface two, characterize the material with DNA. otherwise all class
Hard, transparent, composed of silica, brittle, exhibits conchoidal fracture. Vary kinds
Class Characteristics of Glass
Density, Refractive index, fractures, color, thickness, fluorescence, markings
Immersion method- lowered into liquids whose refractive index is different
Match point- when the refractive index of the glass is equal to that of the liquid
(shadow that appears around an object immersed in a liquid) Disappears and there is minimal difference between he glass and the liquid
Glass Refractive Index Measurement- a computer attached to a video system that views the glass fragments as heat is applied to the liquid medium in a hot stage. The match point tempt is converted to a refractive index using data from the computer.
Radial fracture pattern
Radiate out front the origin of the impact; begins on opposite side of force
Circular lines around the point of impact; begins on the same side as the force
Radical cracks form a right angle on the reverse side of the force
Glass crack rules
High velocity projectile leaders wider hole on exit side of glass Cracks terminate at their intersections with others.
Locard was actually a forensic geologist, sample earthen materials that have been transferred between objects and analyze for origins or sources.
Probative value of soil
# of kinds of earth material is unlimited, changes rapidly over short distances, wide distributions, evidential value. This value increases with rare minerals, rocks, fossil, manufactured particles
Class characteristic Soil
Type of soil may have similar characteristics at the primary and/or secondary crime scene, on the suspect or on the victim.
Only if the soil has an unusual characteristic such as pollen, seeds, vegetation, or fragments.
Natural particles with a grain diameter, color and contents is dependent upon the parent rock and surrounding plant and animal life.
Class characteristics Sand
Composition is based material of the source; gives sand its color
texture is determined by the way the source was transported. (grain size, shape, sorting)
Individual Characteristics Sand
Only if the sand has an unusual characteristic
Study of plant material and relationship to crime scene investigation. (plant remains can be found almost everywhere, offers macro/microscopic evidence, structure allows identification of the plant and allows gathering of info)
Study of pollen and spores. Variation in size and weight, dispersal pattern and produced in given area.