Forensic Toxicology

Forensic Toxicology

Definition: - the study of the chemical and physical properties of toxic substances and their physiological effect on living organisms

A forensic toxicologist must consider the context of an investigation, in particular any physical symptoms recorded, and any evidence collected at a crime scene that may

narrow the search, such as pill bottles, powders, trace residue, and any available chemicals.

“All substances are poisons, there is none which is not a poison. The right dose differentiates a poison from a remedy.” (Paracelsus, 1493-1541)

Important Factors

Dose makes the poison The concentration of the chemical How the interaction takes place

Deaths Investigated by Toxicologists1. Accidental Poisonings

2. Drug Abuse Cases

3. Suicidal Poisonings

4. Homicidal Poisonings

Toxicological Analysis of Tissue

a. Collect sample of all body fluids

b. Collect samples from organs and tissues

c. A forensic toxicologist cannot simply look for the presence of a toxin or drug in a body, he must understand how the body processes these molecules

d. Toxicological analysis must start as soon as possible after a person’s death

Samples to be Analyzed in Forensic Toxicology

Urine Blood Hair sample Oral Fluid Other Body Fluids Other Samples

Urine

Common among drug testing for employees and athletes. A urine sample is quick and easy for a live subject Urine is less likely to be infected with viruses such

as HIV or Hepatitis B than blood samples. Many drugs have a higher concentration and can remain for much longer in urine than blood.

Collection of urine samples can be taken easily which does not require professionals for collection.

For example: Marijuana use, which in heavy users can be detected in urine for up to 14 days.

Blood

10 cm³Blood Sample  is usually sufficient to screen and confirm most common toxic substances

A blood sample provides the toxicologist with a profile of the substance that the subject was influenced by at the time of collection; for this reason, it is the sample of choice for measuring blood alcohol content.

Hair sample

Hair  is capable of recording medium to long-term or high dosage substance abuse.

Chemicals in the bloodstream may be transferred to the growing hair and stored in the follicle , providing a rough timeline Chronology of drug intake events.

Head hair grows at rate of approximately 1 to 1.5 cm a month, and so cross sections from different sections of the follicle can give estimates as to when a substance was ingested.

Some Ethical Facts

Testing for drugs in hair is not standard throughout the population. The darker the hair the more drug that will be found in the hair.

If two people consumed the same amount of drugs, the person with the darker hair will have more drug in their hair than the lighter haired person when tested.

Oral fluid

The use of oral fluid is gaining importance in forensic toxicology for showing recent drug use, e.g. in clinical settings or investigation of driving under influence of substances.

Oral fluid is the proper term, however saliva  is used commonly.

Oral fluid is composed of many components and concentrations of drugs typically parallel to those found in blood.

Other Body Fluids

Other bodily fluids and organs may provide samples,

particularly samples collected during an autopsy . A common autopsy sample is the gastric contents , which can be useful

for detecting undigested pills or liquids that were ingested prior to death. In highly decomposed bodies, traditional samples may no longer be

available. The vitreous humours from the eye may be used, as the fibrous layer of the eyeball and the eye socket of the skull protects the sample from trauma.

Other common organs used for toxicology are the brain, liver, spleen and stomach contents.

Detection Of Drugs

Detection of drugs and pharmaceuticals in biological samples is usually done by

1. An initial screening and 2. then a confirmation of the compound(s), 3. Include a quantitation of the compound(s). 4. The screening and Confirmation are usually, but

not necessarily, done with different analytical methods.

Testing Times….

The choice of method for testing is highly dependent on

what kind of substance one expects to find and

the material on which the testing is performed. Biological samples are more complex to analyze

because of factors such as the metabolism and conjugation of the target compounds.

Forensic Drug Analysis

Addiction

Physical vs. Psychological addiction Physical

causes withdrawl symptoms (any physical or psychological disturbance (as sweating or depression) experienced by a drug addict)

Ex: Alcohol, Narcotics, Depressants

Psychological addictionThe condition of using something on a regular or dependent basis

Dopamine release: In the brain, dopamine functions as a neurotransmitter—a chemical released by nerve cells to send signals to other nerve cells. The brain includes several distinct dopamine systems,

• one of which plays a major role in reward-motivated behavior. Most types of reward increase the level of dopamine in the brain, and

• a variety of addictive drugs increase dopamine neuronal activity.

Ex: Cocaine

Classification of Drugs

Narcotics Reduce sensation – sleep like state morphine, heroin, codeine, fentanyl Both physically and psychologically

addictive Stimulants

Stimulates, speeds up, the central nervous system (CNS)

amphetamines, cocaine, nicotine Psychologically addictive

Methods of Detection1. Color test

2. Chromatography

a. thin-layer chromatography (TLC)

b. gas chromatography (GC)

c. high performance liquid chromatography (HPLC)

3. Microcrystalline test4. Spectroscopy

a. UV light d. X-ray

b. visible light e. infrared

5. Immunoassay

Color test ▪ THC screening….. Marijuana and Hashish▪ Drops added to vegetation, turns purple

color

Screening for Marijuana

Confirmed at the Lab

Chromatography = separation of mixtures Thin Layer (TLC) Gas chromatography (GC) Liquid chromatography (LC) Paper chromatography

Thin Layer Chromatography (TLC) Marijuana is a mixture of compounds

Components spread out in solvent

TLC of Marijuana

Components of various sizes and solubilities travel further

Microscopic ExaminationMicroscopic Examination of Marijuana

Green Plant Material Must be dry, in paper Microscopic Examination

Microcrystalline test

Chemical reagent is added which causes crystals to form

Crystals have different shape depending upon what drug

Cocaine Methamphetamine

Immunoassay

Immunoassay Based on antigen-antibody binding

specificity Antibody produced by injecting antigen

(drug) into rabbit Antibodies will bind to drug in urine

Confirmation done w/TLC

Heroin

marijuana

Interpretation of Findings

1. Is a drug or poison present? What substance?

2. How much of the substance is present?

3. Is it’s concentration in the body sufficient to cause death?

4. How was the drug/poison administered?