question

What is trace evidence?

answer

a generic term for small, often microscopic material. it is physical evidence of contact, and can become a significant part of an investigation.

question

this chapters discusses ways trace evidence is____

answer

collected, preserved, identified, and used

question

What is the Locard Exchange principle?

answer

a concept of transfer,when a person comes into contact with another person/environment, there are some small changes that take place. something is added or taken away. \"certain small and seemingly insignificant changes occur\"

question

what is the importance of transferred trace evidence?

answer

it links suspects to victims or locations

question

Who is the bad guy?

answer

suspect, perpetrator,

question

who is the good guy?

answer

victim

question

sources of trace evidence means

answer

places/hosts of where trace evidence can be found/is on.

question

types of source of trace evidence

answer

trace evidence can be found: on clothes (fibers/hairs on clothes), footwear, on the body, tools, weapons

question

how can trace evidence stick to clothes?

answer

static electricity or become caught in the fabric

question

things to know about clothes as a source of trace evidence:

answer

-collect clothes from the suspect and victim asap (bc evidence/fibers can be dislodged) -make the suspect undress on clean wrapping paper, so the paper will catch any trace evidence that might fall from the clothing -collect clothing, tag the clothing, marked and packaged in paper bags (NEVER PLASTIC BC THAT MAKES MOLD/MILDEW) -dont shake the clothes in the bag because it could dislodge the evidence -if the clothes are wet/bloodstained,they should first be allowed to air dry before packaging -keep suspects clothing away from any sources of trace evidence

question

clothes should be packaged in ___bags

answer

PAPER

question

If known samples from the scene have been collected as exemplars, they should never be packaged with the suspects clothing.

answer

because if he says he wasn't at the seen, then none of the samples should be found on his clothing right?

question

sentence that makes things clear

answer

officers at the scene collected samples of roofing, tar, wood, and plaster to be used as exemplars for any trace evidence that might be found on the suspect.

question

known samples=

answer

exemplars

question

what happens once the clothes have been put in a PAPER bag?

answer

submitted to the crime laboratory for careful examination

question

what if there is a hair/small fiber that could be dislodged on the shirt?

answer

carefuly packaged it in a test tube, pill box, paper fold, post-it note, or other appropriate container. Naturally, the location of this evidence should be noted and the items appropriately marked for identification.

question

how to solve improper evidence handling by emergency medical personnel when they are acting to save someone's life/an emergency?

answer

have police agencies attempt to educate them. crime laboratory personell should be advised to paramedics cut off pieces of clothing, etc.

question

how to collect clothes from deceased victims

answer

before the victim is undressed, the body should be carefully examined for trace evidence by the investigator. An alternate light source can be used in locating trace evidence. The clothing should be carefully removed and placed onto wrapping paper.-if wet from blood, let the clothes air-dry before placing into paper bags

question

Next type source for trace evidence: footwear

answer

shoes have dust, soil, debris, vegetation, or bloodstains on them -useful in shoe impression evidence comparison

question

how should shoes be packaged?

answer

INDIVIDUALLY PACKAGED TO AVOID CROSS CONTAMINATION

question

what happens if there is soil stuck to the shoe?

answer

particular care must be taken when packaging footwear evidence containing clumps of dried soil. make sure the soil does not become dislodged on its transmission to the laboratory

question

Next type source for trace evidence: evidence from the body

answer

Injuries-show signs of struggle -microscopic particles of gunshot residue are often present on the hands of a shooter -hair found on the victims body in rape cases -bloodstains on a victim or suspects body during an assault/murder -CLOSE examination of head, ears, fingernails scraping, and hands may yeild trace evidence so be on the lookout

question

other objects for sources of trace evidnece

answer

tools and weapons, and other objects

question

how to package tools?

answer

but in cardboard box and secure it with zip ties. If the tool/instrument has parts that could fall off-they should be removed and placed in appropriately labled containers.

question

Larger items can also be sources of trace evidence

answer

such as a car, search the car for trace evidence on the scene (if the lab doesnt have a car lot to bring to car to investigate)

question

microscopic evidence can be seen

answer

with high and low power light microscopes, scanning electron microscopes, various types of spectrigraphic tools-its not hard, it is common place to find trace evidnece! :) -it isn't a problem

question

A far greater problem than the SIZE is the QUANTITY of the material brought into the lab

answer

...

question

Collection and preservation of trace evidence

answer

there are legal and scientific aspects to collecting and preserving trace materials

question

what are some of the legal issues regarding trace evidence?

answer

chain of custody, search warrant, court orders are needed-investigators should contact the district attorney for guidance

question

commonly asked question: is it better to remove an item of trace material from a larger item or leave it alone?

answer

the answer is: it depends. If a hair, fiber, lose paint chip, or other very small easily lost item of evidence can reasonably be expected to become dislodged or lost from the item of origin, the smaller item should be removed. If the investigator thinks it will not be lost, then it should not be removed.IT IS PREFERABLE TO SEND THE TRACE EVIDENCE ATTACHED WITHOUT BEING REMOVED.

question

what is something is too large to transport/send to the lab?

answer

trace material should be carefully removed, packaged, and sent to the lab for examination

question

when possible

answer

send photographs of from where the trace evidence was taken from.

question

small items of evidence should always be ____ packaged

answer

double

question

what to mark on the containers?

answer

mark these things on BOTH of the containers: person doing the packaging, date/time, case number, brief description of the item

question

the known exemplars should never be packed with the

answer

questioned samples

question

examples of trace evidence:

answer

building materials, asbestos, safe insulation, paint, rust, metals, textiles/fibers, buttons, cordage and rope, cigarette/tobacco, matches, burned paper, ash, soil, chips and wood splinters, sawdust, wood meal, particles of finely powdered wood, plant material, glass, broken panes of glass, objects left at a crime scene (paper, articles of clothing, product markings), foodstuffs, hair, feathers, electrical wires, broken tools, tape, headlamps,

question

first example of trace evidence: building materials

answer

materials such as stucco, cement, brick, mortar, plaster, sheetrock, plasterboard, window glass, wood and paint constitute evidence generally considered as building materials.

question

where is building material trace evidence most likely to be found?

answer

on the clothes of burglars (in their cuffs, pockets, shoes), or the tools used to break into the location

question

additional building material as trace evidence info:

answer

-examine the point of entry, and take exemplars from it -If tool marks are present, samples of building material should NOT be taken from the area of the tool mark, but rather adjacent to the mark. don't cut through the tool mark -collect known specimens from each area of damage/ break in (bc the composition of the building may vary from spot to spot) -package each item of evidence separatly -TOOLS may be useful sources of building material trace evidence-chips of paint, bm, glass, may stick to them (if found on a tool, don't dislodge the evidence, send it into the lab attached to the tool) -search the interior of a suspects truck for building materials (vacuum sweepings), on shirts

question

building material evidence can only demonstrate_____ and cannot be shown to be unique to a specific source. It is valuable as_____ (this is true for most all trace evidence)

answer

class characteristics, circumstantial evidence

question

How can building material be identified?

answer

by physical, chemical, and microscopic means

question

Next type of trace evidence: Asbestos

answer

used to insulate older homes, can be identified microscopically

question

Next type of trace evidence: Safe insulation

answer

suspects clothes, shoes, and tools may yeild safe insulation

question

how can safe insulation be identiffied?

answer

microscopically and chemically

question

Next type of trace evidence: paint

answer

can show if paint came from a specific location if peices are large enough and can be fitted like a jigsaw puzzle back together with it's orginal place of location. (but most often only class characterisitcs can be demonstrated). easier to tell if came from once source if there are many layers of paint

question

how is paint identified?

answer

by physical and chemical properties

question

physical properities of paint

answer

color, layering, weathering, texture

question

chemical properties of paint

answer

solubility and composition

question

in cases where there was forced entry:

answer

take paint samples as close to the area of damage as possible to lessen the possibility that a further away spot had paint composed differently. BUT DONT COLLECT NEAR THE PRY AREA/TOOL MARK LEAVE THAT ALONE dont take a sample from here

question

In a hit and run investigation involving two vehicles, how many paint samples should be collected?

answer

four paint samples, separately packaged. collect a sample from sample A the point of impact that contains a paint transfer from vehicle b. Also collect a standard paint sample that shows no damage but is adjacent to the damaged area. do this with vehicle b as well

question

how to get a paint sample

answer

tap the side of the vehicle with a pocketknife and let it fall onto a pieve of paper. DO NOT PACKAGE A PAINT SAMPLE IN AN ENVELOPE OR PLASTIC BAG. package in folded paper or a small box with a good seal. Include the substrate

question

Rust

answer

rust may sometimes be confused with bloods stains but can be differentiated by a chemical test

question

Metals

answer

can be identified chemically or spectrographically. Metal filings (from doorknobs) can be found on teeth wrenches used in burgarly cases.

question

textiles and fibers

answer

torn fabric used to gag victims, left clothing at crime location, a portion of fabric may be physically fitted into another piece of fabric (individual characterists-came from one source location) as well as class characteristics. physical, chemical, and microscopic properties-thread count, dye, color, direction of yarn twist, etc. fiber evidence can be transfered from blankets, etc.

question

trace evidence that can have individual characteristics

answer

anything that can be jigsaw fitted into something else. Paint, textiles (clothing pieces/fabric BUT NOT FIBERS)

question

If textile evidence is found at the crime scene it should be:

answer

its location should be noted. Indicated on a crime scene diagram, and photographed. As with other trace evidence, it is preferable not to remove the textile from the object to which it is attached.

question

five types of textile fibers can be encountered as evidence:

answer

animal fibers (wool), vegetable fibers (cotton/hemp), synthetic fibers (polyester, nylon rayon), mineral fibers (glass wool), and blends of synthetic and nature fibers (such as cotton and polyester)

question

you should leave fibers intact to original object, but if not possible (fall off easily) you can

answer

remove by using forceps, cellophane tape, or vacuum sweeping. Of these three the tape method is probably the best (bc it only collects surface material, whereas a vacuum sweeping collects huge amounts and forceps may not capture the trace evidence). Fiber evidence can never come from one unique source (bc garments today are mass produced).

question

buttons

answer

can usually only be used as trace evidence if thread/piece of clothing was attached to the button.

question

cordage and rope

answer

If they were used to tie up a victim, don't untie the knots ( leave them alone). Cut the rope in another spot and tie it back together with string. The knots could provide to be useful evidence! In strangulation cases, skin cells may be attached

question

cigs and tobacco

answer

identify a brand from a butt (info about what brand a suspect uses could be useful).types of ashes left (smokes pipes?)-shows suspect habits.fingerprints may be found on cigs using the ninhydrin process. dna from the saliva left on the butt. cig box-determine location of sale from numbers on the box.

question

matches

answer

find the book of matches on the suspect. Paper/cardboard matches are most common. saliva found at the end of the match-dna could be on it.

question

burned paper

answer

if found in a metal file box, leave it there and send to lab. otherwise, put paper in rigid cardboard boxes. slide a flat peice of cardboard under charred paper to lift it up.- hand carry boxes to lab bc of their fragile nature. If a paper is burning at the scene-DO NOT PUT OUT THE FIRE. do not separate layers of paper, just turn it all into the lab

question

how to read burned documents?

answer

chemical treatement, photography, and examination under ultraviolet and infared light can make the writing legible.

question

how can ash be identified?

answer

microscopically, chemically, or by means of spectroscopy. the source of the ash may be difficult to determine.

question

what is the common type of ash in arson cases?

answer

residue of burned highway flares.

question

what does the ash contain a significant level of?

answer

strontium (responsible for the bright red color of the flare)

question

soil as trace evidence

answer

can be found on shoes, underside of a vehicle-impression evidence on soil-can tie a suspect/car to a place.

question

what is soil

answer

a mixture of decaying and weathered rock and decomposed organic material known as humus. minerals are in it such as quartz, feldspar, and mica, as well as decomposed leaves, pine needles, pollen grains, and other plant fragments. THUS IT IS EASY TO DIFFERENTIATE SOILS FROM VARIOUS LOCATIONS BY MICROSCOPIC EXAMINATION

question

how should soil be collected?

answer

it should be collected in various regions at the specific location in question, and several feet away from it, and at other locations (such as the subjects home or work) for elimination purposes.

question

Where should you place soil specimens?

answer

known samples can be placed in individual small glass jars, such as clean baby food jars. METAL CONTAINERS SHOULD BE AVOIDED.

question

how much of the soil should be taken?

answer

two or three tablespoons of TOPSOIL (DO NOT dig deeper than an inch bc the subsoil may have a different composition)

question

Wood

answer

can take the shape of many forms: sawdust, splinters, chips, large pieces used as assault weapons, etc. wood can have tool marks on it

question

Wood trace evidence is ___ valuable

answer

most....it is possible to identify, compare and match sources of wood evidence.

question

what are the two types of wood?

answer

hard woods and soft woods. It is possible to determine the type of wood and type of tree from pieces the size of sawdust particles (WHOA)

question

how is the examination of wood done?

answer

microscopically.

question

the ____rings of a tree are very characteristic

answer

annual

question

read the section on wood-it is confusing

answer

...

question

plant material

answer

wood, leaves, seeds, bark, twigs, and pollen-attached to clothing, found in a vehicle, etc. fragments of plant material are hard to identify, so botanists from a museum are likely to be sought out for help.

question

What type of plant material is useful to know if a suspect was in an area with flowered plants?

answer

pollen....vacuum sweeps of a suspects clothes may yeild microscopic pollen grains.

question

GLASS ASS ASS ASSS ASSSS

answer

broken glass may yield information about the direction and speed of a projectile, and, in the case of multiple projectiles, the sequence of events (this is importante!!)

question

Broken panes of glass

answer

was it broken from the outside of inside/struck by a bullet or a rock?....how to find out:

question

What can determine from which direction the force came from that caused the glass to break?

answer

rib markings

question

what are the two types of glass fractures?

answer

radial and concentric

question

how to determine the direction of force?

answer

by examining the rib markings along the edges of radical and concentric fractures

question

when examining rib marks of radial fractures

answer

look at the right angles..the side without the right angles is the side that the force was applied opposite side-concentric is the other way around

question

how to send glass to a lab?

answer

the pieces should be individual wrapped in paper.the wrapped evidence may be placed together in a box for easier transportation.

question

high velocity bullets leave:

answer

an almost circular hole in a pane of glass without noticable cracking or with cricks merely starting

question

lower velocity bullets leave:

answer

an almost regular polygon with radial cracks running outward.

question

a shot at very close range:

answer

more or less completely shatters the glass from the pressure of the muzzle gases-in such cases it is impossible to obtain a clear idea of the appearance of the shot hole. evidence of a shooting at close range-gun shot residue on the glass. sometimes you can metal around the ridges of glass that it when through (spectrographically).

question

difference between rock and bullet holes:

answer

the crater-like expansion of a hole caused by a small stone may not show the same uniform fracture in the glass as a bullet hole would. holes caused by small stones do not show the same geometric regularity in the radial and concentric cracks in the glass around the hole as that is shown by a bullet hold. Large stone can shatter a piece of glass if thrown at close range-thus you should search for the projectile that did the damage

question

order of cracks? If multiple

answer

radical cracks produced by the first incident stop by themselves or run to the edges of the glass.the cracks on the subsequent incident stop when they meet the cracks already present from the earlier fracture

question

cracked or burst panes of glass

answer

...

question

glass cracked by heat shows

answer

characteristic long wavy fractures. pieces fall out in the same direction as the source of heat.

question

objects left at the crime scene

answer

paper, such as newspaper, wrapping paper, can be left behind-handwriting, latent fingerprints can be found. torn or cut peices, can find matching peices in the suspects home.stains may be used to show connection to another site

question

articles of clothing

answer

clothing left at a scene can show the nationality of the wearer, and the size, laundry marks. Initials could be found inside the clothes. if dried blood is found on clothing, you can look for DNA.

question

what is foodstuffs? cosmetics?

answer

foodstuffs in the form of stains or debris can be used to determine the type of work the suspect does. if starch is found in the vacuum sweep, the suspect could have been baking.

question

Hair as trace evidence

answer

hair should use 2 things:microscopic hair evaluation should be couples wth DNA testing. mitochondrial DNA testing if the shaft is present, nuclear DNA testing if there is a root)

question

what can hair tell us?

answer

species, location, growth place on the body, hair treatment, hair disease, if hair fell out naturally or pulled

question

how to search for hair?

answer

flashlight and a pair of twezers.

question

how many hair should be collected from the head to use an exemplars?

answer

25

question

Chapter 8: Blood, Forensic biology, and DNA

answer

...

question

what can deoxyribonucleic acid (DNA do)?

answer

determine the identity of unknown human remains, tie a suspect or victim to a crime scene, establish paternity, and identity the unknown prepertrator to a cold case.

question

safty procautions

answer

people working with wet or dried blood should use PPE personal protective equitment such as tyvek suits, lab coats, gloves, masks, and goggles/face shields. ppl should get hepitis vacinations. blood could have HIV, etc. so it is dangerous.

question

_____ should be worn when working with any biological products (blood, saliva, semen)

answer

surgical gloves

question

______ gloves should be used when scraping an item for DNA evidence with a razor blade.

answer

cut resistant

question

how to dispose of biological evidence?

answer

use commerical disposal companies that specialize in biohazardous material waste.

question

____is a big concern when handling biological evidence

answer

contamination. try to eliminate dna transfer. collected items of evidence should be packaged separatly. KNOWN AND QUESTIONED SAMPLES SHOULD NEVER BE PACKAGED TOGETHER.

question

What should tools be wiped down with to avoid cross contamination??

answer

10% bleach, followed by 70% ethanol.

question

any individual in a crime scene should submit their dna in case their was contamination/transfer (used as elimination samples)--They will NOT be uploaded to CODIS

answer

...

question

what is the name of the national DNA database?

answer

CODIS COmbined DNA Indexing System

question

Blood pattern analysis-what ccan it do?

answer

the shape, grouping, and distribution of bloodstains can assist the investigator in reconstructing what took place at the crime scene. Determines the movement and direction of the person, the sequences of events, the area of origin, the number of impacts during an incident, and the object used to create the pattern.

question

what are the three basic classifications of bloodstains?

answer

passive, spatter, and altered

question

what are the two types of bloodstains?

answer

impact spatter (blood that travels through the air from an impact mechanism), and transfer stains (stains resulting from contact with a bloody surface)

question

a pointed of tail end of a bloodstain indicates direction of travel.

answer

...

question

equation for the angle of impact

answer

=arc sin(width of ellipse)/(length of ellipse)

question

who is the BPA?

answer

The Scientific Working Group on Bloodstain Pattern Analysis

question

Presumptive tests for blood aka catalyic tests

answer

may be used to search for small amounts of blood, or note that its blood if they think it might be something else. They are chemical tests and can be used to see if a suspect cleaned up the crime scene.

question

HOWEVER

answer

Presumptive tests are NOT confirmatory tests for blood.

question

names of the presumptive tests

answer

leucomalachite green, phenolphtalein, orthotolidine, tetramethylbenzidine, luminol

question

Presumptive tests are ____ tests that depend on the properties of ______

answer

color spot....hemoglobin (the oxygen carrying material found in blood). a positive result can result from human or animal blood, as well as some plant material so be careful

question

which two PTs are the most specific?

answer

phenolphthalein and leucomalachite green

question

which two PTs are the most sensitive?

answer

orthotolidine and tetramethylbenzidine

question

generally, the _____aka Kastle Mayer test is a good overall choice

answer

phenolphthalein

question

how is phenolphthalein conducted?

answer

on filter paper or on cotton-tipped swabs. PERFOMRING THE TEST DIRECTLY ON EVIDENCE SHOULD BE AVOIDED. then kastle mayer reagent is added, then a drop of 3% hydrogen peroxide....color will change from clear to pink if hemoglobin is present

question

____can be purchased at a drug store and was used to test for blood in urine

answer

Hemastix

question

what is the luminol test good for?

answer

very useful for searching for large areas of blood, specifically blood that has been cleaned up.

question

what are the drawbacks to the luminol test?

answer

room must be completely dark bc blood reacts with luminol by giving off light, a process called chemiluminescence. The reagent is sprayed with an aerpsol sprayer. the glow given off is faint. The test works best on older stains.-bleach can cause a false positive.

question

what is a better test than luminol and why?

answer

bluestar forensic latent bloodstain reagent-is nontoxic, total darkness is not required, has stronger luminescnce, longer lasting reactions, and higher sensitivity.

question

Postive presumtive test plus DNA test are both needed to indicate the presence of human blood. OR

answer

The Hexagon OBTI test allows the investigator to confirm the presence of human blood.

question

What color is a dry but relatively fresh bloodstain?

answer

reddish brown color and glossy. in a very thing layer the color may be grayish green. the gloss slowly dissapears.

question

color change on blood is ____ on metal surfaces and ____ on textiles

answer

quicker, slower

question

how to search for stains

answer

use lights, colored lights, red, green, white or infared lights.

question

how to record blood stains

answer

describe their form, size, color, position, direction of splash--

question

the best way to preserve the appearance of bloodstains if through____

answer

photography-overall, medium, and close up range shots (close up range should provide a scale)-also a sketch-(a drop of blood located 25 inches from the floor and 16 in east of the doorway om the north kitchen wall indicating a downward direction.

question

collection and preservation of bloodstains

answer

air dryed sample in a paper bag at room temperature. it does degrade over time in certain environmental conditions.

question

_____the specimans down slows down deteriroation

answer

drying.....DO NNOT place in air tight containers, or damp environments

question

why is it important to save evidence for awhile?

answer

some defendants need to use it in court and the evidence must be preserved. or else the case could be thrown out.

question

how to collect wet blood?

answer

place a cottown swaab into the still liquid pool of blood. or filter paper or cotton gauze. sterlyl cotton tip applicators...let air dry, then place in a coin enveleop

question

most blood found at crime scenes is ____

answer

dry.can collect with a cotton ball with distilled water on it. let it dry, place in an envelope, mark it

question

for very small stains, it is best to ____the blood on one area of the swab rather than spread it around the entire surface of the swab

answer

concentrate.

question

Bloodstained objects

answer

it is best to bring the entire blood stained object to the lab. If the blood apepars lose and flaky, then it should be collected and sent to the lab. packaged air dryed blood stained objects loosely in paper bags.

question

semen stained objects

answer

sexual assault cases.

question

how to identify semen stains?

answer

an alternate light source can be used due to semens flourescent properties under certain wavelengths of light. once a stain is located, a presumptive test is done to determine if the stain is indeed semen.

question

what are the presumptive tests for semen?

answer

looking for acid phosphate (AP)-color spot test that changes from clear to reddish-purple. after the PT another test must be done-either look microscopically for sqimming spirm, or detect Prostate specific antigen (PSA) or p30.

question

Forensic DNA typing

answer

...

question

how to collect DNA

answer

buccal swipes are taken (inside of a cheek)-an excellent alternative to collecting blood samples.

question

DNA typing is based on our_____

answer

genetic makeup

question

differences has a root in

answer

genetics, mid 19th century, gregor Mendel

question

DNA is the biochemical key to differentiating uniqueness amoung individuals.

answer

twisted ladder, double helix, the steps within the ladder consist of four chemical subunites or bases

question

what are the names of the bases

answer

guanine (G) Adenine (A) Thymine (T) and Cytosine (C)

question

the bases always pair in this way

answer

AT, CG

question

DNA is folded into microscopic bundles called

answer

chromosomes

question

chromosomes exist in the celll

answer

nuclei

question

____ blood cells contain DNA

answer

white

question

what has DNA?

answer

blood, semen, bone marrow, tissues, hair roots, dandruff, saliva, tooth pulp

question

How to examine DNA?

answer

using a Polymerse chain reaction procedure (PCR) or is known as STR analysis

question

PCR is

answer

a technology that copies short segments of DNA millions of times in a process that resembles the way in which DNA naturally duplicates itself in the body. It is a powerful method bc it can applied to any body sample no matter how small.

question

how PCR works

answer

extracts DNA from the cells, separates the DNA double helix into two strands by HEATING the sample. A PCR mixutre is then added. has DNA primers (Short segments to indicate the target segment of DNA to be copied), DNA polymerse (an enzyme), and the four nucleotide bases ACTG.

question

what type of instrument is a PCR performed in??

answer

thermocycler, repeated for 28 cycles.

question

after DNA is separated, then it goes through a process called

answer

capillary electrophoresis.---eventually data is converted to electronic data into an exlectropherogram

question

high sensitivity DNA testing/touch DNA

answer

used to detect and recover small amounts of DNA--increased cycle number for PCR and interpretation methods. example items to be used:car swabs, handles of weapons, keys, pens, air bags.

question

mitochondrial DNA

answer

mitochondira are found in the cytoplasm of most cells.they are the engery for the cell.

question

how does mtDNA differ from DNA

answer

-mtDNA is much smaller molecule (circular shaped) -it is only inherited maternally -is present within a cell in multiple copies bc there are many mito in the cell

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