What are Forensic Toxicologists?
Charged with the responsibility for detecting and identifying the presence of drugs and poisons in body fluids, tissues, and organs.
Forensic toxicologists not only work in crime labs and medical examiners' offices, but also...
Reach into hospital labs and health facilities to identify a drug overdose or monitor the intake of drugs.
A major branch of forensic toxicology deals with what?
Measurement of alcohol in the body for matters that pertain to violations of criminal law.
The analysis of alcohol exemplifies the primary objective of forensic toxicology:
The detection and isolation of drugs in the body for the purpose of determining their influence on human behavior.
Where is alcohol the most heavily abused drug?
How many deaths each year are attributed to alcohol intoxication?
What part of the body does alcohol principally affect?
Central nervous system, particularly the brain.
Blood alcohol concentration has been shown to be directly proportional to the...
Concentration of alcohol in the brain.
3 Aspects of Alcohol's Fate in the Human Body:
When does alcohol appear in the blood?
Within minutes after is has been taken by mouth and slowly increases in concentration while it is being absorbed from the stomach and the small intestine into the blood stream.
The longer the time for complete absorption to occur...
The lower will be the peak alcohol in the blood for a given number of drinks.
What does alcohol become when absorption is complete?
Uniformly distributed b/w all the watery portions of the body, which is about 2/3 of body volume.
In descendants, if blood is not available, what other watery portions of the body can be used to determine alcohol levels?
Cerebrospinal fluid, brain, or vitreous humor.
Elimination of alcohol throughout the body is accomplished through...
Oxidation and excretion.
Where does oxidation take place entirely?
Where the enzyme alcohol dehydrogenase converts alcohol to acetic acid and then into carbon dioxide and water.
Where does about 5% of alcohol go in the body?
Excreted unchanged in the breath, urine, and perspiration.
How is blood alcohol concentration defined?
Percent weight per volume.
-Hence, 0.10% is equivalent to 0.10 grams per 100 milliliters of blood.
Experimental evidence has verified that the amount of alcohol exhaled in the breath is in direct proportion to what?
The blood concentration and is directly proportional to alcohol in the brain.
The current legal measure of drunk driving in the US is a BAC of how much?
0.08%, or 0.08 grams of alcohol per 100 milliliters of blood. Another way of expressing this is 80 mg/dL.
The temperature at which the breath leaves the mouth is normally:
34 degrees celsius.
1 milliliter of blood contains nearly the same amount of alcohol as:
2,100 ml of alveolar breath.
Many types of breath testers are designed to analyze what?
An individual's breath as it flows through a chamber in the breath tester and is exposed to infrared radiation.
What kinds of breath testers are becoming popular?
One's that operate on the principle of infrared light absorption.
What allows an infrared light absorption instrument to measure a BAC in breath?
The degree of interaction of the infrared light with alcohol in the breath chamber.
What are Fuel Cells?
Some breath testing devices use these to convert the alcohol to an electrical current.
Why do law enforcement officers use sobriety tests?
To an estimate a motorist's degree of physical impairment by alcohol and whether or not an evidential test for alcohol is justified.
What are Psychological Field Tests?
1) Horizontal Gaze Nystagmus Test
2) Walk and turn
3) One leg stand
What is Gas Chromatography?
Most widely used approach for determining alcohol levels in forensic labs.
What do hospital or clinical labs normally use to measure alcohol content?
How do autoanalyzers measure alcohol content?
They measure the conversion of alcohol to acetaldehyde by alcohol dehydrogenase.
-The determination is made as a serum alcohol level.
How is serum alcohol normally converted to a BAC?
By the factor 1.16. Thus 250 mg/dL is equivalent to 215 mg/dL of .215.
Whom must always be drawn under medically accepted conditions?
By a qualified individual.
What must be applied to a suspect's skin before it is penetrated with a sterile needle or lancet?
A nonalcoholic disinfectant.
Once blood is removed from an individual, its preservation is best ensured when it is:
Sealed in an airtight container after an anticoagulant and a preservative have been added and stored in a refrigerator.
Failure to properly preserve blood removed from living individuals may result in what?
A decline of the blood alcohol levels.
What type of laws have all 50 states established regarding BAC?
Per Se Laws
What are Per Se Laws?
Any individual at a defined BAC (normally 0.08%) shall be deemed to be intoxicated.
How likely is a driver to become involved in an accident when BAC is at 0.08% and 0.15%?
- 4 times more likely to be involved at 0.08%
-At 0.15%, chances rise to 25 times.
What have all of the states adopted to prevent a person's refusal to take a test for alcohol consumption?
Implied Consent Law
What is the Implied Consent Law?
This law states that the operation of a motor vehicle on a public highway must either consent to a test for alcohol intoxication, if requested, or lose his or her license for some designated period.
Shmerber v. California (1966)
The Supreme Court ruled that the taking of blood samples was not protected by the 5th amd.
Missouri v. McNeely (2013)
Ruled that police should obtain a search warrant prior to the drawing of a person's blood for alcohol testing.
Beyond the analysis of alcohol, the toxicologist is confronted with what in particular?
A maze of drugs and poisons.
-The toxicologist is originally presented with body fluids and/or organs and is normally requested to examine them for the presence of drugs and poisons.
The strategy used for identifying abused drugs entails a two-step approach:
What are the two most widely used screening tests?
1) Gas Chromatography
What are the two most accepted confirmation tests?
1) Gas Chromatography
2) Mass Spectrometry
What does gas chromatography do?
Separates the sample into its components.
What does mass spectrometry do?
Represents a unique "fingerprint" pattern that can be used for identification.
The combination of the gas chromatograph and the mass spectrometer enables forensic toxicologists to do what?
Separate the components of a drug mixture and provides specific identification of a drug substance.
What four heavy metals do forensic toxicologists examine?
-They occasionally are encountered b/c severe environmental protection regulations restrict their availability to the general public.
What does a toxicologist must do to screen for many of the heavy metals?
The suspect body fluid is dissolved in a hydrochloric solution and a copper strip is inserted into the solution.
What is the screening test for non drug poisons?
The Reinsch Test
-The presence of a silvery or dark coating on the copper indicates the presence of a heavy metal.
What do non drug poisons must be confirmed through?
The use of techniques suitable for inorganic analysis.
What are the 3 Confirmation tests for non drug poisons?
1) Atomic absorption spectrophotometry
2) Emission spectroscopy
3) X-ray diffraction
What is one of the most common poisons encountered in a forensic lab?
Carbon monoxide, which is absorbed by the red blood cells.
To measure the concentration of carbon monoxide in the blood, what do spectrophotometric methods do?
Determine the amount of carboxyhemoglobin relative to oxyhemoglobin, or total hemoglobin.
To measure the concentration of carbon monoxide in blood, what happens to a volume of blood?
Be treated with a reagent to liberate the carbon monoxide, which is then measured by gas chromatography.
What are some toxicologists required to provide once the drug is extracted?
An opinion on the drug's effect on an individual's natural performance or physical state.
For many drugs, what is readily determined and can be used to estimate the pharmacological effects of the drug on the individual?
Blood concentration levels.
Why is the preference blood for indicating how extensively an individual's behavior or state is influenced by the drug?
Urine is a poor indicator.
What must the analyst consider before drawing conclusions about drug-induced behavior?
Other factors such as age, health, and tolerance.
What added benefit do toxicologists have when dealing with a living person?
Knowing what a police officer may have observed about an individuals behavior and motor skills.
What did the LAPD develop in the 1970's?
Clinical and psychophysical examinations that a trained police officer could use to identify and differentiate b/w types of drug impairment.
-This program has evolved into a national program to train police as drug recognition experts.
How long is the program to certify an officer as a drug recognition expert?
What standardized methods have the DRE program incorporated?
Blood pressure, pulse, pupil size, for examining suspects to determine whether they have taken one or more drugs.
-Process is standard and systematic.
-30 to 40 min.
-A Drug Influence Evaluation form must be completed.
-12 step process
-7 categories of dr
What can the DRE program usually cannot determine?
Which specific drug was ingested, but what category. Impairment?
-Hence, it is the production of reliable data from BOTH the DRE and the forensic toxicologist that is required to prove drug intoxication.
What is plasma?
The fluid portion of the body.
-Composed of principally water and accounts for 55% of blood content.
What are the 3 solid materials found in plasma?
1) Red blood cells (erythrocytes)
2) White blood cells (leukocytes)
What are antigens?
Usually proteins and carbs, are located on the surface of red blood cells and are responsible for blood-type characteristics.
What are antibodies?
The proteins in plasma.
What is the fundamental principle of blood typing?
For every antigen, there exists a specific antibody.
What are antibodies normally?
Bivalent- they have 2 reactive sites.
What does bivalent mean regarding antibodies?
An antibody can attach to antigens located on two red blood cells forming a network of cross-linked cells seen as clumping or agglutination.
How many blood antigen systems have been identified?
What blood antigen systems are most important?
A-B-O and Rh.
What % of the population has type O blood?
What % of the population has type A blood?
What % of the population has type AB blood?
What is the Rh factor is determined by?
The presence of another antigen, the D antigen.
What are people who have the D antigen?
Rh positive versus those who don't have the antigen which are Rh negative.
Where has the concept of specific antigen-antibody been applied to?
Immunoassay techniques for detecting drugs-of-abuse in blood and urine.
What doesn't antibodies that react with drugs not do?
Exist naturally; however, they can be produced in animals by combining the drug with a protein and injecting this combination into the animal.
What are Polyclonal antibodies?
When an animal, such as a rabbit or mouse, is injected with an antigen its body will produce a series of different antibodies, all of which are designed to attack some particular site on the antigen of interest.
collection of antibodies
What are monoclonals?
A more uniform and specific collection of antibodies designed to combine with a single antigen site.
What immunological assay technique used to detect drugs through antigen-antibody reaction?
Enzyme-multiplied immunoassay technique (EMIT)
Why is enzyme-multiplied immunoassay technique (EMIT) used?
B/c of its speed and high sensitivity for detecting drugs in urine.
What does a typical EMIT analysis consist of?
Antibodies that will bind to a specific drug are added to the subject's urine.
-This is followed by adding to the urine a chemically labeled version of the drug. A competition will ensue b/w the labeled and unlabeled drug to bind with the antibody.
What 3 Q's must a criminalist be prepared to answer when examining dried blood?
1) Is it blood?
2) From what species did the blood originate?
3) If the blood is of human origin, how closely can it be associated to a particular individual?
What test is the best to determine blood?
Preliminary Color Test
What is a positive result from the Kastle-Meyer (Preliminary color test) color test?
highly indicative of blood.
What does hemoglobin cause?
A deep pink color.
What tests are used to search out trace amounts of blood located at crime scenes?
Luminol Test, or Bluestar.
-Luminol is extremely sensitive and is capable of detecting blood that has been diluted up to 100,000 times.
What does the Luminol, or bluestar, test produce?
Light in a darkened area.
Once the stain has been characterized as blood, what test will determine whether the stain is of a human or an animal?
What does the Precipitin test use?
Antisera normally derived from rabbits that have been injected with the blood of a known animal to determine the species of origin of a questioned bloodstain.
What is gel diffusion?
Takes advantage of the fact that antibodies and antigens diffuse or move toward one another on an agar plate.
-The extracted bloodstain and the human antiserum are placed in separate holes opposite of each other on the gel. If the blood is human, a line o
What efforts must be made once a bloodstain has been determined to be of human origin?
Associate or dissociate the stain with a particular individual.
What has allowed forensic scientists to associate blood to a single individual?
What is the basic unit of heredity?
What is a chromosome?
Threadlike structure in the cell nucleus along which the genes are located.
What is each gene composed of?
DNA specifically designed to carry the task of controlling the genetic traits of our cells.
What is a locus?
The position a gene occupies on a chromosome.
-Appx. 30,000 human genes have been identified.
What do most human cells contain?
46 chromosomes, arranged in 23 mated pairs. The only exceptions are the human reproductive cells, the egg and sperm, which contain 23 unmated chromosomes.
During fertilization, a sperm and an egg combine so that:
each contributes 23 chromosomes to form the new cell, or zygote, that develops into the offspring.
What is an allele?
Any of several alternative forms of genes at a particular locus and that are aligned with one another on a chromosome pair.
A heterozygous gene pair is made up of how many alleles?
2 different alleles
A homozygous gene pair is made up of how many alleles?
2 similar alleles.
When 2 different genes are inherited, what will happen when the characteristic is coded for by a dominant gene?
Will be expressed
-The characteristic coded for by a recessive gene will remain hidden.
What is the transmission of hereditary material accomplished by?
Means of microscopic units called genes, located on chromosomes.
What are alternative forms of genes that influence a given characteristic (such as eye color or blood type) known as?
Paternity testing has historically involved with what system?
A-B-O blood typing system, along with blood factors other than A-B-O.
Currently, paternity testing has implemented DNA test procedures that do what?
Can raise the odds of establishing paternity beyond 99%.
Why is it necessary to examine exhibits for the presence of seminal stains?
Many of the cases sent to forensic labs involve sexual offenses.
What is the best way to locate and at the same time characterize a seminal stain?
Perform an acid phosphatase (an enzyme secreted into seminal fluid) color test.
A purple color indicated what enzyme?
Acid phosphatase enzyme.
What can sperm be specifically identified with the presence of?
Spermatozoa, or tentatively identified by p30, a protein present in seminal plasma.
Forensic scientists can successfully link seminal material to an individual by what?
The sexual victim must undergo what?
A medical examination as soon as possible after the assault.
At that time the appropriate items of physical evidence are collected:
pubic hair controls (25)
external genital swabs
swabs of body areas such as breasts
head hairs (25)
All outer and undergarments should be carefully removed and packaged in what?
separately in paper bags
If a suspect is apprehended within 24 hrs of an assault, it may be possible to detect what?
The victim's DNA on a male's underwear or on a penile swab of the suspect.
What are the 5 Items routinely collected from the suspect?
1) All clothing
2) Public hair
3) Head hair
4) Penile swab
5) Blood sample or buccal swab for DNA typing.
The forceful physical contact b/w victim and assailant may result in a what?
transfer of such physical evidence of blood, semen, saliva, hairs, and fibers.
The Persistence of Seminal Constituents in the Vagina: Motile sperm
The Persistence of Seminal Constituents in the Vagina: Non-motile sperm
The Persistence of Seminal Constituents in the Vagina: Seminal Acid Phosphatase
Less than 48 hrs.
The Persistence of Seminal Constituents in the Vagina: Prostate Specific Antigen
Less than 72 hrs.
Before the collection of biological evidence begins, what other evidence is important?
Evidence to be photographed and recorded on sketches.
What are you required to wear while handling evidence?
Disposable latex gloves
The packaging of biological evidence in plastic or airtight containers must be avoided why?
B/c the accumulation of residual moisture could contribute to the growth of DNA-destroying bacteria and fungi.
Each stained article should be packaged how?
Separately in a paper or well-ventilated box.
All biological evidence should be what?
Refrigerated or stored in a cool location until delivery to the lab.