Forensics 4

Name two physiological factors and two nondrug factors that influence drug dependence

Headaches and depression caused by withdrawal. Person's expectations of the drug, societal responses or pressures to using.

Under what class of drugs is cocaine listed according to U.S. federal drug laws? Explain why this classification is pharmacologically incorrect.

It is listed as a narcotic (a depressant), it is a stimulant.

What is the source of most narcotic drugs? From what plant is this substance derived?

Opium, poppy plant

What opium derivative is most widely used by addicts? How is it typically administered? Give two reasons why this route of administration is popular.

Heroin. It is typically administered via injection, but it can be smoked. Injection is popular because of the speed of effect and the strength of the effect.

What is the most widely used illicit drug in the United States? Under what class of drugs is it listed and what are its short-term physical and psychological effects at low to moderate doses?

Marijuana. Hallucinogen.

Physical- restlessness, hunger, relaxation

Psychological- wellbeing, hilarity, relaxation

What is the most widely abused drug in the United States? Under what class of drugs is it listed, and what are its short-term physical and psychological effects at low to moderate doses?

Alcohol. Depressant.

Physical- confidence, impaired coordination

Psychological- impaired judgement, memory, and concentration

How can excessive use of depressants cause death?

overdose can cause the CNS to stop sending signals to breathe to the lungs and diaphragm

Name the two most commonly abused illegal stimulants and the smokable forms of each. Why does smoking provide a more intense drug experience than inhaling, or "snorting," stimulants?

Cocaine and amphetamines.

Crack cocaine and ice methamphetamine are smoked.more intense due to the direct induction into the blood stream through the lungs as gases and the immediate distribution to the brain. Inhaled substances are solids must dissolve and pass through the mucous membrane before entering the blood stream.

Name two club drugs that are associated with drug-facilitated sexual assault, rape, and robbery. Why are these drugs relatively easy to administer to an unsuspecting victim?

Gamma hydroxybutyrate (GHB) and rohypnol. They are easy to administer to victims because they are alcohol soluble and are odorless, colorless, and tasteless in the victim's drink.

What is the most popular club drug? Name three negative health effects associated with chronic use of the drug.

The most popular club drug is methylenedioxymethamphetamine (MDMA, ecstasy, X).

On what three criteria does the Controlled Substances Act classify dangerous substances?

Physical dependency, psychological dependency and medical uses.

According to the Controlled Substances Act, what is the legal difference between a schedule I drug and a schedule II drug?

Both have high risk of dependency but schedule I drugs are considered to have no medical uses while schedule II drugs are considered to have them.

What is a controlled substance analog? Why are such substances considered schedule I drugs?

Controlled substance analogs are designer drugs. Designer drugs have not been FDA analyzed therefore they have no known medical uses and their risk of dependency is not known.

What is a precursor? How is possession of a precursor treated under the Controlled Substances Act?

A precursor is a chemical used in the synthesis of a drug. Precursors are listed under the class of the drug they could be used to manufacture.

List and describe the two phases in a criminalist's scheme of action for identifying a drug.

A criminalist two phases of identifying a drug are classifying it (presumptive analysis) and identifying it (individualization).

What two goals must laboratory testing accomplish to positively identify a drug?

Successful separation from other non-illicit substances and positive identification of illicit substances.

How does a color test work? What is the main limitation of a color test for identifying drugs?

A color test works by creating a colored product characteristic of a class of drug. The main limitation is that substances other than a drug of interest may produce a false positive result.

Describe how a microcrystalline test works. Name two advantages of microcrystalline tests.

add a chemical reagent to a drug on microscope slide, soon producing a crystalline precipitate. the size and shape of crystal is characteristic of a drug. tests are (1)rapid and (2) do not require isolation from the dilutants in the drug.

Briefly describe the basic chromatographic process. Be sure to explain how motion is important to the process.

Basic chromatographic processes include the movement of a mixture through a stationary phase with which each component has a different level of interaction. The greater the interaction the more slowly a component moves, this causes the development of separated "bands" of each component. In chromatography flow of the mobile phase provides the means of movement of the sample mixture components. In gas chromatography only the flow rate of the gas matters to the separation. In liquid chromatography the components will also have solubility in the mobile phase that competes with their stationary phase interactions.

What two chromatographic processes are most applicable for solving analytical problems typically encountered in the crime laboratory?

The two methods of chromatography most used in forensics laboratories are gas chromatography and thin layer chromatography.

What is the most important drawback to gas chromatography?

The most important draw back to gas chromatography is that the samples analyzed must be volatile.

How are ultraviolet spectrophotometry and infrared spectrophotometry used in drug analysis?

Uv-vis spectrophotometry can be used to confirm the presence of some analytes but is mostly used to quantitate the amount of substance in a sample. IR spectrophotometry can be used to confirm the identity of a substance unambiguously and it can also be used to quantitate the amount of a substance in a sample.

What is Beer's law and what analytical technique is based on it?

Beer's law states that the absorbance of a substance is equal to its absorptivity times its pathlength times its concentration. If is frequently used in UV-vis spectrophotometry but is applicable to all forms of electromagnetic spectrophotometry.

What is the main strength and main weakness of ultraviolet spectrophotometry?

The main weakness of ultraviolet spectrophotometry is that absorption bands of substances are broad and if overlapping not distinctive enough to unambiguously identify a substance. The main strength of ultraviolet spectrophotometry is that it is relatively quick to obtain quantitative information for a sample.

What major advantage does infrared spectrophotometry enjoy over ultraviolet spectrophotometry?

IR spectrophotometry has the main advantage over ultraviolet spectrophotometry of sample specificity.

In what area does mass spectrometry currently have its greatest application for forensic scientists?

Identification of pure samples.

List at least three factors that determine the rate at which alcohol is absorbed into the bloodstream.

Quantity and type of food in the stomach at the time of drinking, total time taken to consume the drink, alcohol content of the beverage, and amount of beverage consumed.

Name and describe the process by which most alcohol is eliminated from the body. How is the remaining alcohol eliminated, and how is this useful in testing for alcohol?

Oxidation, where the alcohol is oxidized to create oxygen and water for the body. The main alcohol is excreted and unchanged in breath, urine, and perspiration. One can smell the alcohol on one's breath.

Why is a blood test for alcohol taken shortly after drinking more advantageous for the suspect than one taken 30 minutes or more after drinking?

The levels will not increase from artery to veins

What was the first successful breath-test device and what did it measure to determine blood-alcohol concentration? What is the main difference between this device and the breath-test devices currently in use?

Breathalyzer, to measure the alcohol content of alveolar breath. Modern tests are free of chemicals

What is the key to the accuracy of a breath tester? Describe two steps the operator takes to ensure that this key requirement is met.

That the alcohol in the alveolar breath of the subject is captured, unaltered, by strong substances put in the mouth, seconds or minutes beforehand.

What is horizontal gaze nystagmus and how does the test for it reveal blood-alcohol levels?

The involuntarily jerking of the eye as it moves to the side. The higher the concentration of blood alcohol causes the eye to jerk at smaller angles, or jerking begins before the eyeball has moved 45 degrees to the side.

What is a divided-attention task? Name and describe two divided-attention tasks often administered during field sobriety tests.

A test of the subjects ability to comprehend and execute two or more simple instructions at one time. A walk and turn test requires this subject to maintain balance while standing heel to toe. The one leg stand requires the subject to maintain balance on 1 foot for at least 30 seconds.

What substances are typically added to blood that is collected from a subject before it is sent to a toxicology lab, and why are they added?

coagulates to stop clotting, and preservatives to keep microorganisms from growing

At what blood-alcohol level is a typical driver in the United States considered legally intoxicated? At what blood-alcohol level is a commercial truck or bus driver in the United States considered legally intoxicated?

Typical driver: 0.08. commercial driver: 0.04.

What is metabolism and how does it complicate the task of the forensic toxicologist?

Transformation of a chemical in the body to other chemicals. Few substances will leave in the same state.

Why is it necessary to follow a positive screening test for drugs with a confirmation test? What is the confirmation test of choice?

To confirm beyond any reasonable doubt that another substance didn't trigger those positives. Microcrystalline tests work well.

A body is found at a fire scene but investigators are not sure whether the victim was alive when the fire began. How can measuring the level of carbon monoxide in the victim's blood help determine this?

A person deceased before a fire begins will not have elevated levels of CO in the blood since there was no respiration occurring.

Why is knowledge of an individual's history of drug use important in evaluating drug concentrations found by a toxicologist?

A frequent user might have a high tolerance while an infrequent or new user will have a low tolerance. The tolerance level can be used to explain the nature of an overdose or the observed behavior of a person.

What is the A-B-O system?

System for classifying blood type. DNA has replaced it because it is so much more specific.

What is an antigen and how is it useful in individualizing blood?

An antigen is a protein on the surface of a cells, human cells can have type A, B, both or no antigens.

What is an antibody, and what happens when an antibody reacts with its specific antigen?

An antibody is protein exogeneous to a cell that binds to a specific type of antigen.

What factor is most whole blood typed for? What is the most common blood type in the United States? Which is least common?

A-B-O identity. O is most common. AB is least common.

For what other application do forensic scientists often use specific antigen-antibody reactions?

Matching blood types in a crime scene.

What three questions must the criminalist be prepared to answer when examining dried blood?

Is it blood, From what species did the blood originate, if the blood is human origin, how closely can it be associated to a particular individual.

List two commonly used color tests for blood. How does a luminol test differ from these tests?

Kastle-Meyer test and Hemastix test. The luminal test produces light rather than color.

What is the purpose of a precipitin test? Name three strengths of precipitin tests.

It determines if a blood stain is human or animal. Sensitive, requires small amount of blood for testing, and blood stains dried for years can still give reaction.

What is a genotype and how do parents' genotypes affect the blood type of their offspring?

A genotype is the particular combination of genes present in the cells of an individual, and a person's genotype or blood type is decided by their parents. Area of the law is determining maternity, child custody, etc.

What is acid phosphatase and how is it used by forensic scientists?

Acid phosphatase- An enzyme found in high concentrations in semen. Locating semen stains, use it to find present of semen in stain.

List three reasons why spermatozoa are often not found in seminal fluid collected at a crime scene.

Sperm stains are brittleSperm binds together tightly to cloth material, like underwearMale involved in the case can have a low or zero sperm count.

Why is it important for investigators to seek information about when and if voluntary sexual activity last occurred before a sexual assault?

If a rape victim had consensual sex, sperm may remain in vaginal cavity at the time of the examThis info will help in evaluating the significance of finding the seminal constituents in female victims.

What is complementary base pairing? What is the importance of the order in which base pairs are arranged?

It is the specific pairing of base A with T and base C with G in double-stranded DNA. There are no restrictions on how the bases are to be sequenced on a DNA strand.

How are proteins formed? What determines the shape and function of a protein?

They are formed by linking a combination of amino acids. It is determined by the sequence of amino acids in a protein chain.

Describe the process of DNA replication. What is the importance of DNA replication?

It begins with the unwinding of the DNA strands in the double-helix. It allows a cell to pass on its genetic identity when it divides.

What is polymerase chain reaction (PCR) and how is it useful to forensic scientists?

PCR is a laboratory method of increasing the number of specific DNA sequences so that they can be more easily detected.

What are tandem repeats and how are they useful to forensic scientists?

Tandem repeats are noncoding filler DNA sequences that occur between genes. These sequences appear through out the human population but each person (other than identical twins) has a different set of these.

What are short tandem repeats (STRs) and what is their significance to DNA typing?

STRs are the tandem repeats that are used to identify individuals (other than identical twins) by DNA typing. The FBI only uses 20 STRs in the DNA typing of individuals placed into CODIS.

What is multiplexing and why is it used in DNA profiling?

Multiplexing is the simultaneous isolation, duplication, and analysis of STRs reducing the time needed to make a DNA identification from sample cells much less time consuming.

What characteristics are revealed by the amelogenin gene and Y-STRs?

The amologenin gene can identify whether the DNA is from a male (XY) person or a female (XX) person.

How should packages containing DNA evidence be stored? Name one common exception and explain why it should be handled differently and how it should be stored.

DNA evidence should be stored in paper bags or ventilated boxes to prevent bacteria decomposition. An exception made is DNA Evidence on soil which should be frozen to prevent soil microbes from degrading the DNA sample.

What is the threshold amount of DNA needed for analysis? What are some possible sources of DNA?

The threshold amount of DNA for court admissibility is 125 pg, about the amount in 18 cells. Buccal swabs, toothbrushes, hairbrushes, razors, soiled laundry, ear plugs, cigarette butts, or anything where skin tissue may be deposited.