chem final

toxicology

study of drugs, poisons, toxins and effects of harmful substances on the body

drugs

any substance that effects the structure / functioning of a living organism, widely used for the prevention, diagnosis, and treatment of disease / relief of symptoms

poison

natural or manmade chemicals that can cause severe harm and/or death, can either be a drug or a toxin depending on if it’s manmade

toxin

substances created naturally by plants, animals, or fungi that are lethal to humans

stimulants

increase energy and alertness and decrease appetite

narcotics

interact with opioid receptors to reduce intensity of pain signals and feelings of pain, misuse results in feelings of euphoria

depressants

relieve anxiety and reduce sleep

hallucinogens

effect perception, thinking, self-awareness, and emotion

anabolic steroids

promote cell / tissue growth

controlled drugs

any drug regulated by law / restricted in some way, need prescription or can only possess so much

over-the-counter drugs

can be purchased legally without prescription

illicit drugs

not legally permitted, not normally used for medical reason or illegally obtained

pharmacokinetics

movement of drugs through the body

absorbtion

drug enters the system via ingestion, inhalation, injection, or topically

distribution

chemicals move through the body via circulatory system based on molecular structure of drug

blood-brain barrier

membrane drugs have to cross to get to the brain is very difficult

metabolism

formation of byproducts (metabolites) as chemical is broken down into the body

excretion / elimination

drug / byproducts are eliminated / exit the body through urine, feces, sweat, or breath

presumptive tests

initial detection of drugs to narrow down possibilities, do not confirm or quantify, just detect

marquis test

different substances produce different coloured reactions

microcrystals

different substances produce different crystal shapes

universal indicator

pH scale, scott’s reagent

scott’s reagant

turns blue / green colour when cocaine is present

confirmatory tests

based on preliminary results, confirm identity and sometimes quantity of drug compounds, single test that conclusively identifies a substance

mass spectrometry

gold standard but destroys compound in the process, identifies compounds based on mass, from different combinations of elements, and fragmentation patterns, how molecules break apart

infrared spectrometry

identify compound based on unique way its components absorb infrared light, compare to known database to find matches based on size / location of peaks

raman spectrometry

identify compound based on different way Raman component elements scatter light, similar to infrared but with visible light

x-ray diffractometry

identify crystalline (solid) compounds by determining atomic structure from measuring how x-rays are diffracted

chromatography

components of sample mixture are separated based on their different affinities for two separate phases, different components travel through stationary phase at different rates

mobile phase

moves along stationary phase and drags compounds with it, can be liquid or gas

stationary phase

does not move, compound and mobile phase move along it, can be solid, or solid-liquid mixture like gel

paper chromatography

stationary phase - paper

mobile phase - solvent (liquid)

cheap and simple but separation can be poor

compound moves far up → strong reaction with solvent

compound stays near bottom → strong reaction with paper

thin layer chromatography

stationary phase - plate coated with silicon gel

mobile phase - solvent (liquid)

more expensive but fast and can tolerate corrosive agents

RF value

substance rate of migration determined by affinities for mobile vs stationary phase, comparing results to known substances, preliminary

liquid chromatography

stationary phase - column packed with solid

mobile phase - liquid

separates liquid samples like 3D TLC

retention time (RT)

time it takes for compound to move through column and hit detector at other end, comparing to known substances, preliminary

gas chromatography

stationary phase - solid 30-50 m long column

mobile phase - non-reactive gas

separates vaporized (gas) samples, compares RT to known samples

gas chromatography-mass spectrometry (GCMS)

gold standard confirmatory test, compound enters GC as a mixture and is separated into individual components that enter MS as single compound, MS creates plot unique to that compound by positively charging the molecules and separating the ions based on mass

plasma

liquid in which other components are suspended, 54% of whole blood, contains all the formed elements

red blood cells

carry respiratory gasses through blood, 45% of whole blood, responsible for blood’s red colour

white blood cells

immune system cells to protect against disease, 0.7% of whole blood, only blood cells with DNA that can identify a person

cohesion

molecules bonded together to make blood fall as spheres

passive drop

falls straight down (90º) due to gravity to produce spherical droplet

higher drop

larger diameter of spatter

elliptical drop

results from different angles of impact

direction of travel

follows the tail

steeper angel of impact

more elongated drop

gravity produced

passive drops falling from gravity, pool pattern from blood flowing in one place for considerable amount of time

transfer bloodstains

wet bloody surface comes into contact with another surface and transfers blood from original location, shows directionality

wipes

object moves through preexisting bloodstain

swipes

person bleeding is being moved

spatter bloodstains

something sends the blood flying

greater force of impact

smaller diameter of drop

cast off

object swung in arc flings blood

expired

blood blown out through mouth or nose

DNA profiling

isolate and amplify DNA, examine non-protein coding regions, use electrophoresis to separate DNA fragments by size with electricity

lysing cells

detergent breaks apart cell membrane

PCR

makes copies of short DNA regions

3 steps of PCR

denaturation, annealing, extension

denaturation

high temp separates DNA double helix into two separate strands by breaking hydrogen bonds

annealing

low temp binds primers to set of sequences on a single DNA strand, initiates base pairing and duplication of DNA

extension

moderate temp binds nucleotides (A,C,T,G) to complimentary base pairs on each individual strand

RFLP

takes copies of DNA made from PCR and cuts them at specific sequences to produce DNA fragments with lengths unique to each individual

gel electrophoresis

separated DNA fragments after RFLP, allows us to see individual fragments under UV light and determine their size to create DNA profile

short tandem repeats

shorter DNA sequences of 2-6 bases that repeat in ways that are specific to the individual, 22 loci used for DNA examination and profiling, length varies based on number of repeats at each locus

capillary electrophoresis

negatively charged DNA moves through positive end of electric field, carried through tubes, DNA labelled with coloured fluorescent tags and detected as capillary flows past a detector

electropherogram

one allele inherited from each parent, two peaks correspond to the two alleles, peaks show number of repeats at each of the loci, numbers below are the number of repeats, number at each locus is put in a database to be compared

preblast

bomb has not gone off, investigators can examine the explosive

postblast

bomb has been detonated, investigators must piece the scene together and reassemble the explosive by collecting material

primary blast injury

victim most likely deceased, closest to explosion

secondary blast injury

victim hit with shrapnel, fragments, or other objects propelled by the explosion, causing blunt force trauma, severe bleeding, or possible loss of limb

tertiary blast injury

victim falls or is thrown against hard surface by force of the explosion

matrix

items that have residue from the blast on them

explosive evidence examination

ion mobility spectrometry, acetone and H2O wash, TLC, and infrared

entomology

scientific examination of insects that shows how long bugs have been associated with the body to interpret how long it has been since death

fresh

24-72 hours, body typically intact

bloat

3-5 days, body begins to digest itself, releasing gases and causing bloating

active decay

8-10 days, organs, muscle, and skin begin to liquify, limbs turn black

advanced decay

10-25 days, body almost completely liquefied

skeleton remains

no set time for when this occurs

body farms

study timeline of decay and insects found at each stage

entomotoxicology

analyze toxins and byproducts found inside insects

blow flies

speedy flies often first at body, lay eggs in wounds with predictable larval development

flesh flies

slow flies common in later stages of decay, lay live maggots in wounds

rove beetles

speedy beetles feed off larvae and can disrupt flies’ life cycle

skin beetles

slow beetles arrive in advanced decay and eat dry parts like hair and skin

larvae / maggot development

predictable life cycles indicate time of death

successional ecology

predict insect types based on area, season, and habitat to estimate time of death

botany

plant science in forensic investigation to determine potential manner of death, create geographical profile, link suspect to crime, confirm alibi, and identify murder weapon

limitations to botany

CSIs not adequately trained to identify plants of specific species and family, evidence may mold, dry, deteriorate, or alter from original form, identification can be challenging due to lack of significant plant remains

ballistics

examine bullets and cartridges fired to commit a crime

cartridges

compare impression left by firing pin and breech-face marks, class evidence from manufacturing marking, colour, and material

bullets

compare rifling marks left as it travels through the barrel, unique to each firearm, individual evidence from chamber and ejection marks

ghost guns

don’t leave marks on bullets, no serial number, can be dissolved

arson

deliberately setting fire in criminal act

reasons for committing arson

personal reasons such as revenge, symbolic reasons such as religion or public statements, cover up to hide / destroy something, murder / suicide attempt, mental illness, or profit from insurance / fraud

most common target of arson

residential buildings

arson and blood evidence

fire alters hemoglobin and alters the blood evidence

detection dogs

alert owner for accelerant and can find fire’s point of origin

portable arson sampler

collects any residing fumes / residue