Forensic Toxicology
Ensure that specimens are not contaminated by other materials.
Avoid Contamination
Try to collect forensic specimens as soon as possible.
Collect Early
All specimens must be clearly labelled with the patient’s name and date of birth, the health worker’s name, the type of specimen, and the date and time of collection.
Label Accurately
Specimens should be packed to ensure that they are secure and tamper-proof.
Ensure Security
Once a specimen has been collected, its subsequent handling should be recorded.
Maintain Continuity
Other information about the victim must be properly documented for the purpose of the investigation.
Document Collection
Procedure for Collection:
• Samples should be collected ___________ after death.
without delay
Procedure for Collection:
If an autopsy cannot be performed within few hours after death, ____________________ is usually the unique procedure to minimize alterations in the concentration due to ____________ changes.
mortuary refrigeration, putrefactive
Name three basic procedures that can be implemented in the procedure for collection of specimen.
- blind femoral blood collection through the body surface
- urine by catheter
- suprapubic puncture
The purpose of _____________ is to provide a representative part of the whole that is suitable for screens and confirmations.
sampling
Which of the following materials is preferred for collecting biological fluids and tissue specimens?
Glass containers
What is the primary reason for sealing specimens immediately after opening a cadaver?
To preserve specimen integrity
True or False: Glass containers are used for biological fluids because they contain fewer contaminants than plastic containers.
True
True or False: The choice of sample container is always the same, regardless of the intended analysis.
False
Why should a container be as full as possible when storing samples?
To minimize air exposure
Which type of containers are preferred for most samples, except for volatile substances?
Plastic containers
What is the recommended temperature for long-term specimen storage?
-20°C to -80°C
Which specimen types are stable at room temperature?
Hair and nails
Why should whole blood not be frozen if plasma or serum is required for analysis?
Freezing alters the structure of plasma or serum
True or False: Specimens for short-term storage should be kept at 4°C.
True
True or False: Decomposition during post-mortem periods can make storage and analysis more difficult.
True
What can complicate analytical results from post-mortem specimens?
Decomposition and tissue liquefaction
Which preservative is commonly recommended for blood samples?
Sodium fluoride
Why must alcohol not be used as a preservative when the suspected poison is phosphorus?
Alcohol prevents the detection of phosphorus’ luminosity in the dark
Which preservative should be used for tissues intended for histological examination?
10% formalin saline solution
True or False: Sodium fluoride is effective in preventing the conversion of glucose to ethanol in blood samples.
True
True or False: Formalin is an ideal preservative for toxicological examination of organic poisons.
False
What is the most effective preservative for viscera, organs, or tissues, except in specific poisoning cases?
Absolute alcohol
A forensic lab receives viscera for toxicological analysis three weeks after the individual’s death. Upon examination, the poison is not detected. What could be the most likely reason for this failure to detect the poison?
Delay in the examination of the viscera
Viscera samples from a suspected poisoning case are stored at room temperature without any preservative for a week before being examined. Upon analysis, no poison is detected. What is the most probable cause for the failure to detect poison?
Improper preservation of the viscera
In a case where a plant-based toxin is suspected, the toxicologist uses a method designed to detect heavy metals. The test results come back negative for poison. What is the most likely reason for this non-detection?
Use of wrong analytical technique
A highly unstable organic poison is believed to have been administered. However, upon analysis, no traces of the poison are found in the viscera. Further investigation reveals the poison breaks down rapidly in biological tissues. What is the most likely explanation for this non-detection?
Early disintegration of the poison
A person is suspected to have ingested a fast-acting poison that is rapidly metabolized by the liver. Upon toxicological analysis, no poison is found in the viscera even though poisoning is suspected. What is the most likely cause of this?
Complete metabolization of the poison in the body
Which organ is particularly useful for interpreting blood findings during post-mortem toxicological analysis?
Liver
Which biological sample is most appropriate for identifying substances that have been recently ingested?
Gastric content
Which two organs are the most commonly analyzed tissues in toxicological analysis?
Liver and kidney
True or False: Re-collection of biological specimens is often possible if proper preservation is not followed during post-mortem analysis.
False
Name four organs that are frequently collected during toxicological analysis.
- Liver
- Kidney
- Brain
- Lung
How much cardiac blood is typically collected for toxicological analysis?
30 mL
Which chamber of the heart is preferred for collecting cardiac blood samples during post-mortem analysis?
Right chamber
True or False: Cardiac blood is collected primarily for screening due to its limited volume.
False
Why are blood clots collected from the subdural, subarachnoid, or epidural spaces considered "time capsules"?
Due to poor perfusion, they preserve the blood composition at the time of injury
How much blood is typically collected from subdural, subarachnoid, or epidural spaces for analysis?
30 mL
True or False: Blood clots from these spaces can be used to estimate blood concentrations at the time of injury because of poor perfusion.
True
How much blood is used for analysis of blood from thoracic and abdominal cavities?
30 mL
Exhaled air is primarily used to analyze which type of substances?
Volatile xenobiotics
How much amniotic fluid is typically collected for toxicological analysis?
10 mL
What is the primary purpose of collecting amniotic fluid for toxicological analysis?
To evaluate intrauterine xenobiotic (XB) exposure at an early stage of fetal development
List two conditions that can be assessed using exhaled air samples.
- Ethanol ingestion
- Carbon monoxide poisoning
How much bile is typically collected for toxicological analysis during a forensic autopsy?
10 mL
Why is bile collected before the liver during an autopsy?
To reduce the risk of contamination from liver tissue
What makes bile analysis challenging?
The presence of bile salts
True or False: Bile concentrations of xenobiotics can be influenced by post-mortem diffusion from the liver and stomach.
True
What is the typical volume of peripheral blood collected for toxicological analysis?
10 mL
Which vein is typically used to collect venous blood in post-mortem examinations?
Femoral vein
Which anticoagulant should be used ante-mortem to obtain plasma from peripheral blood?
Lithium Heparin
What is the approximate total volume of blood in an adult human body?
Approximately 5-6 liters
List two veins that can be used for venous blood collection during post-mortem examinations.
- Femoral Vein
- Subclavian or jugular vein
What is the typical volume of urine collected for toxicological analysis?
30 mL
Which method is used for postmortem urine collection in internal examination cases?
Inserting the needle directly from the bladder
Why is urine considered an ideal sample for screening approaches?
It has high concentrations of parent xenobiotics and metabolites
What is the typical volume of gastric contents collected for toxicological analysis?
30 mL
How is cerebrospinal fluid (CSF) typically collected?
By lumbar puncture
Why is the total volume of ingested substance in gastric contents important?
It can reveal overdose, even if the concentration is low.
True or False: No apparent correlation exists between cerebrospinal fluid concentrations and blood concentrations of xenobiotics.
True
What is the volume of the plastic universal container used for brain specimen collection?
30 mL
Which type of substances are primarily analyzed in brain specimens?
Lipophilic and volatile XBs
What factor makes the extraction of lipophilic substances from brain tissue challenging?
Substances being tightly bound to lipids
What is the typical weight of the lung sample collected for toxicological analysis?
30 g
What type of substances are primarily analyzed in lung specimens?
Volatile XBs and paraquat
From which part of the lung should the sample be collected?
Apex of the lung
What is the typical weight of the liver sample collected for toxicological analysis?
30 g
Which part of the liver is preferred for sample collection to avoid contamination?
Deep right lobe
Why should the gallbladder be excluded when collecting a liver specimen?
It may contain bile, which can contaminate the sample
What is the typical amount of kidney tissue collected for toxicological analysis?
30 g
In toxicological analysis, kidney specimens are primarily collected for which of the following types of analysis?
Metals or ethylene glycol
Before submitting the kidney for toxicological analysis, which part of the kidney should be removed?
Renal capsule
What is the typical amount of heart tissue collected for toxicological analysis?
30 g
What is the typical amount of hair collected for analysis from the posterior vortex region?
160-200 hairs
What types of exposure can hair analysis help assess?
Drug of abuse exposure history and chronic heavy metal exposure