forensics chapter 12

Alveoli

Tiny air sacs within the lungs where the exchange of oxygen and carbon dioxide takes place.

Anticoagulant

A chemical that inhibits the coagulation of blood.

Breathalyzer

The original device used to measure alcohol in expired breath; was replaced in the 1990s by other devices. The absorption of light by potassium dichromate is measured before and after its reaction with alcohol present in the suspect's breath. The absorption of light of the suspect sample is compared to a standard. The higher the concentration of alcohol, the more potassium dichromate will react, and less will be available in the vial. Developed in 1954 by Dr. Robert Borkenstein. It was based on Henry’s law which states that “at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.” In humans, the ratio of exhaled alcohol to blood alcohol is 2,100 to 1.

Catalyst

A substance that increases the rate of a chemical reaction without being consumed during that reaction.

DUID

Driving under the influence of drugs.

Effect-based law

Law that requires evidence of impairment to convict someone of DUID

Excretion

The act or process of discharging waste matter from the blood, tissues, or organs.

Intoxilyzer

An instrument that measures IR to determine alcohol in expired breath. Measures the infrared (IR) absorption in a specific wavelength to confirm the presence of ethanol. The amount of IR absorbed by a compound corresponds to the energy it takes to stretch or bend bonds in a specific organic molecule. Each molecule has a unique IR spectrum, but the presence of acetone or acetaldehyde molecules can give a false positive. Unlike breathalyzer, intoxilyzer measures “deep lung” air, not just if there is alcohol in a person's mouth

Fuel cell

A device that directly converts chemical energy into electrical energy through chemical reactions.

Metabolites

The metabolic breakdown products of drugs.

Oxidation

A chemical reaction in which oxygen is combined with other substances.

Per se DUID law

Law in which a person is assumed guilty if drug concentration exceeds a defined limit.

Retention time

The amount of time it takes a compound to be separated via a gas chromatograph.

Vitreous humor

Liquid inside the eye.

Zero tolerance law

Any detectable amount of an illicit substance in the blood constitutes a DUID.

Toxicology

Study of adverse effects of chemicals on living organisms

Postmortem toxicology

forensic scientist or toxicologist identifies and quantifies the presence of drugs, gases, metals, and other toxic chemicals in human fluid and organs and determines, if any, as contributing factors in the individual's death. A postmortem toxicological investigation always begins with a case history of the deceased:
Age, sex, weight, and medical history
Any medication administered before death
Autopsy findings
Drugs that were available to the decedent
The interval between the onset of symptoms and death

Human performance toxicology (behavioral toxicology):

toxicologist measures the amount of alcohol or drugs in a living person's blood or breath and estimates their role in modifying human performance or behavior.

During the autopsy, a pathologist collects postmortem specimens for analysis.

brain 50g, liver 50g, kidney 50g, heart blood 25ml, peripheral blood 10ml, vitreous humor (eye) all available, bile all available, urine all available, and gastric contents all available. All starts with the case history → how was the poison taken? If taken orally: check the gastrointestinal tract (GI) contents first since it may still hold unabsorbed poisons or drugs. Urine should be analyzed next: it may contain intact poison or one of its metabolites. The liver is the next organ that usually has the highest concentration of poisons: the liver detoxifies the body of chemicals – either by oxidizing or reducing the poison or by binding the poison to sugar that is naturally present in the liver.

Poisons

Over 2 million poisonings occur in the US each year
Poisons can be categorized as
-inorganic: mercury, arsenic, lead
- organic: chloroform, ipecac, heroin
- radiological: any radioactive species
- biological: certain plants and disease

corrosive poisons

A substance that destroys tissues on contact. These include strong acids and bases: HCI, H2SO4, NaOH, and KOH. These substances are contained in many household items, such as drain cleaners and car batteries. How dangerous a substance depends on its pH → determined by the concentration of H+ ions. Corrosive compounds attack the peptide bond to break down the protein and damage the tissue.

metabolic poisons

A poison that interferes with essential metabolic processes in the body. Cyanide poisoning (CN) – either as a gas (hydrogen cyanide) or as a solid (potassium or sodium cyanide). It inhibits an enzyme called cytochrome C oxidase. Binds to iron (III) in the enzyme and prevents its reduction to iron (II). If reduction does not occur, oxygen cannot be used by the cells. Carbon monoxide (CO) is a colorless, tasteless, and odorless gas that is a product of incomplete combustion. Makes the skin turn pink and the lips turn cherry red.

Toxic metals

Some metals are toxic in very small amounts. Metals of particular concern include beryllium (Be), cadmium (Cd), chromium (Cr), Lead (Pb), mercury (Hg), Thallium (TI), and arsenic (As). Heavy metals are highly reactive, with sulfhydryl groups (-SH) present in the active site of enzymes involved in oxygen transport. Reinsch Test: works when metal ion reacts in acid to form a colored coat on copper metal. Suspect tissue or blood is dissolved in a hydrochloric acid solution, and a strip of copper is added to the solution. It is a presumptive test. The presence of the metals needs to be confirmed by an analytical test such as ICP-OES or X-ray. The copper has then observed for the results → purple black coat means the metal is antimony, a dull black coat means the metal is arsenic, a shiny black coat means bismuth, and silvery black means the metal is mercury.

Organic poisons

Very common due to availability, even if that is by illegal methods. Are typically administered to an incapacitated victim. Immunoassay tests are used to test the specimens for opiates, barbiturates, and other classes of prescription drugs. Organic poisons can be acidic or basic. Toxicologists can change the pH of a solution by adding an acid or a base to extract a potential poison.
Used to concentrate the poison in order to be used for further analysis.

Interpretation of toxicological information

Once the specimens are analyzed, the forensic toxicologist must assemble the results, study them, and determine the cause of death. Must determine: how much poison entered the body, how much poison was administered, and whether enough poison was ingested to cause death directly or indirectly. The concentration of drugs in postmortem blood is not uniform throughout the body → highest concentration of drugs has been found in heart blood. It has been found to increase as the interval between death and autopsy lengthens. Analysis of specimens allows toxicologists to estimate the “minimal administered dose” of a drug or poison. How is the minimal administered dose determined? Determine the concentration of the drug or poison in as many different organ tissues as possible. The concentration of each drug or poison in each separate organ tissue is multiplied by the total weight or volume of that organ. Add the number of drugs found in all organs: the total amount is the minimal administered dose.

Marijuana DUI and DUID → human performance testing-

The most commonly used human performance tests are those employed to determine whether an individual is driving a car under the influence of alcohol (DUI) or drugs (DUID). Currently, laws governing the use of a motor vehicle after using marijuana are either: effect-based laws: evidence of impairment, per se DUID laws: assumed to be guilty if the drug concentration exceeds a defined level → no requirement to obtain evidence of impairment, and zero tolerance laws.

Immunoassay test for marijuana use

A rapid, on-site oral fluid screening --> mouth swab

Field sobriety testing

Include a structured process such as an officer interview, psycho-physiological tests (eye exam and coordination tests), physical examination of the subject, evaluation of the suspect, evaluation of suspect statements, and toxicology exam (breath, blood, and/or urine).

BAC levels

Alcohol is a depressant that acts on the CNS
Sober 0.00-0.06%, euphoria 0.03-0.12%, excitement 0.09-0.25%, confusion/vomiting 00.18-0.30%, stupor 0.27-0.40%, coma 0.35-0.50%, and death 0.45%, 0.08% legal limit.

Alcohol and the law

In the 1800s, the first sanctions were imposed by the railroad industry.1939, Indiana became the first state to enact a “drunk driving” law in which BAC was used as the basis for determining a person’s sobriety.1964, the Grand Rapids study was published. By 1973, “implied consent” laws required motorists to take a breathalyzer test or face sanctions (lose their license).1980’s found the growth and development of both civilian (MADD) and government groups that pushed for harsher laws against DUI. The US department of transportation recommends that all states adopt a 0.08% BAC as the legal definition of drunk driving
States that had not adopted it lost federal highway construction funds. Commercial drivers have a lower limit of 0.04% BAC.

Grand rapids study

It was the first of its kind to connect motor vehicle crashes to BAC, Provide a scientific base for court cases, and let room open for more research. It took 20 years for the study to finish and establish a scientific foundation for “per se.” Provided reference for minimum penalty thresholds.

Alcohol metabolism-

As ethyl alcohol travels through the GI tract, it is absorbed into the bloodstream (stomach 20%, small intestine 80%)
Once in the bloodstream, the alcohol travels to the brain and affects the CNS. Factors that influence absorption rate: Rate of gastric emptying, Presence of food in the stomach, The concentration of ethyl alcohol, and Rate of alcohol consumption. Ethyl alcohol gets into the body by absorption, which is a slow process. The actual concentration of ethanol in a particular tissue in the body depends on the water content of that tissue → the more water the organ contains, the higher the concentration of alcohol is expected. Ethanol concentrations in the tissues rapidly reach equilibrium with the BAC. During ethyl alcohol’s elimination process, it is transported to the liver, where enzymes catalyze the oxidation of the alcohol
More than 90% of the ethyl alcohol that enters the body is completely oxidized to acetic acid, primarily in the liver
The remaining alcohol that is not metabolized is excreted in either the sweat, urine, or breath

BAC via blood at the time of an accident can be estimated via an equation

C subscript a BAC at the time of the accident
C subscript t BAC measured after the accident
Beta is the rate at which the body removes alcohol
Ranges from 12.5mg/100ml/hr to 25mg/100ml/hr
Average is 18.7mg/100ml/hr

Alcosensor

It is an alcohol fuel cell that consists of a porous, chemically inert layer that is coated on both sides with a platinum layer, which is impregnated with an acid solution and has electrical wires attached to the platinum. It can be connected to a smartphone.

Blood testing

Carried out using a Gas Chromatograph-mass spectrometer (GC-MS). Highly accurate and never gives a high false positive → so accurate almost always admissible in courtBlood must be properly taken and stored in an airtight container → container has an anticoagulant, which is intended to prevent clotting of the blood, as well as a preservative, which inhibit microorganisms from growing and contaminating the sample. In the case of post-mortem testing, blood samples from various locations and sometimes samples of urine and vitreous humor. After a person dies, bacteria grow in the cadaver and produce ethanol, which may lead to a falsely high BAC reading. If blood samples collected from different locations produce similar BAC results in the alcohol content was the result of alcohol consumption by the person before death. When a blood sample is analyzed, the area under the peak is measured. By referring to the calibration curve, the forensic examiner can calculate the concentration of alcohol in the sample.

The ______, ______, and ______ are organs that should be collected for postmortem toxicological analysis.

Brain, liver, kidney

If it is suspected that a poison was administered orally, the ______ should be analyzed first.

GC-MS

Postmortem blood from the ______ has been found to contain higher concentrations of drugs than other parts of the body.

Heart

The most widely abused drug in Western countries is ______.

Alcohol

A BAC of 0.08% is equivalent to ______ grams of alcohol per 100 milliliters of blood.

80 grams

The field sobriety test is a (presumptive/confirmatory) test.

Presumptive

Legislation that triggers sanctions at a certain BAC level is called “______” legislation.

implied consent

Most of the alcohol a person drinks is absorbed into the bloodstream through the ______ ______.

Stomach and small intestine

The higher the proportion of water in an organ, the (higher/lower) the concentration of alcohol.

Higher

Alcohol in the body is oxidized in this organ:______ ______.

liver

More than 90% of the ethyl alcohol that enters the body is completely oxidized to ______.

acetic acid

Alcohol that is not metabolized is excreted in the sweat, the urine, or the ______.

Breath

One milliliter of blood will contain the same amount of alcohol as ______ milliliters of expired breath.

2,100

The more alcohol present in the breath sample, the (greater/smaller) the absorbance observed by the Intoxilyzer.

Greater

The most reliable method of determining BAC is by ______ ______.

Gas chromatography

In badly decomposed bodies, poisons are more likely to be found in the vitreous humor.

false

The rate at which the body removes alcohol from the blood is constant for any one individual.

True

Failure to properly preserve the blood sample will always give a BAC that is falsely high.

False

When sampling blood from a corpse, it is best practice to collect blood samples from multiple sites on the body.

True

ca=ct+(B)t
Ca=70mg/100ml+(12.5mg/100mL/h)(2h)
Ca=95mg/100ml = 0.095%