How Police/investigators Collect the biological/toxicological samples from body and crime scene?

The toxicological sample or evidence are of two types. Antemortem sample and postmortem sample. Antemortem samples are collected when the body is live, nota

FORENSIC SCIENCEFORENSIC TOXICOLOGY

Shubham Kumar

1/29/20247 min read

blue leather boxing gloves on white table
blue leather boxing gloves on white table
person in blue long sleeve shirt holding black stick
person in blue long sleeve shirt holding black stick

We often think that police catch the culprit of murder by the analysis of toxicological sample like blood, blood, or by autopsy. Have you ever wonder about how investigators collect these toxicological samples. Notably, a small defect during collection holds potential to render the prime efforts of experienced forensic toxicologist. Moreover, creates an invisible barrier in the analysis. Therefore, the collection procedure is one of the most important part of legal investigation.

In this article we are going to gain valuable insights on the collection procedures of toxicological samples. Moreover, we will get a deep dive in packaging and storage of the same.

In order to understand the collection of toxicological sample, first you need to understand what exactly toxicological sample is!

Toxicological sample refers to the all the biological material present in the crime scene or related to the crime which are subjected to be analyzed in order to establish the relation between suspect, crime scene and victim. Moreover, finding valuable insights about the crime committed and uncover the telltale from hidden mysteries. The toxicological samples includes blood, urine, bile juice, gall bladder, hair follicles, nails, and organs (widely regarded as viscera). These samples hold prominent grounds in cases like murders, murder by poison, assault by intoxication and in rapes. Therefore, investigators are properly briefed to collect these samples accurately.

The toxicological samples are analyzed by the forensic toxicologist. The forensic toxicologists are the prime scientist of forensic toxicology, look for the potential insights about crime committed by the examination of these toxicological evidence.

Collection and Sealing of Specimens | Toxicological Sample

The toxicological sample or evidence are of two types. Antemortem sample and postmortem sample. Antemortem samples are collected when the body is live, notably, it encompasses blood, urine, vomit, saliva, etc. On the other hand, postmortem sample include viscera. If we compare the potential between these samples, postmortem always regarded as accurate.

Antemortem Samples | Toxicological Sample

The antemortem samples are collected while the victim is alive, moreover, the urgency in analysis of these samples is must. These sample includes blood, urine, saliva, bile juice and another important samples.

When the victim is hospitalized before death, it is essential to submit antemortem samples for analysis if available. The urgency in the antemortem sample is must, therefore, a pathological expert must present to collect these sample.

It is crucial to collect all available antemortem samples; however, caution should be exercised with antemortem serum samples, as the gels used in serum gel tubes may absorb drugs and impact blood concentration. Antemortem samples should be labeled with the date and time of collection.

Blood Samples

Blood samples are the preferred choice when quantitative analysis of drugs is required. It is important not to mix blood samples from different sites, as variations in drug concentration can occur based on the collection time after death, sampling site, method, and volume.

The femoral vein is commonly used for blood collection through percutaneous puncture. Some forensic toxicologists suggest clamping the vein before sampling to prevent blood from inferior vena cava and inguinal vein, but this may add complexity to the autopsy procedure. Another technique involves a blind stick or stab technique to the unclamped external iliac vein.

If femoral samples are not available, venous subclavian or jugular blood can be obtained. Two samples from distinct sites, such as left and right femoral veins, are ideal. It is advisable to place at least 4-5 milliliters of blood into a fluoride preservative tube, specifically provided by the Toxicology Laboratory.

The remaining blood sample can be placed in a plain plastic universal container. If the analysis includes volatile substances, a glass vial should be filled to the top.

In cases where peripheral blood samples are not attainable, cardiac blood may be submitted, but it should be clearly labeled as such. However, the limitations of cardiac blood should be considered, including drug accumulation due to post-mortem redistribution, diffusion, putrefaction, autolysis of cardiac tissue, trauma, and its primary use for screening purposes.

Blood collected from the body cavity is generally not suitable for toxicology analysis due to potential contamination by gut contents, urine, or other body fluids, but if it is the only available option, it should be clearly labeled as such.

Urine Samples
  • Urine samples are valuable for screening unknown drugs or poisons, particularly drugs of abuse. Preferably, at least 10 milliliters of urine should be collected in a plain sterile plastic container, avoiding the use of boric acid containers.

  • Urine can be obtained by direct puncture of the exposed bladder or by inserting a urethral catheter before the autopsy.

  • Aspiration of urine from the dome of the bladder during the autopsy can also be practiced, ensuring no contamination by blood or other fluids.

  • If the patient was catheterized shortly before death, this information should be noted on the request form as the urine sample can be contaminated by local anesthetics.

Liver, Bile, and Stomach Contents | Toxicological Sample
  • Liver tissue can be useful in complex poisoning cases, with a portion taken from deep within the right lobe of the liver. One hundred grams of liver tissue are generally sufficient for most analytical purposes.

  • Bile can be easily aspirated from the gall bladder, even in cases of cholecystectomy, by aspirating the common bile duct with a needle and syringe.

  • Stomach contents are rarely useful; however, if a sample is submitted, one 25-30 milliliter sample without preservative should be collected and clearly labeled.

  • Precautions must be taken when cyanides or phosphides are suspected, as their interaction with stomach acid may release highly toxic hydrogen cyanide or phosphine gas.

Additional Samples
  • In specific circumstances, other samples may be considered. Muscle samples, typically from the psoas muscle, can be useful for screening purposes, although quantitative data may be limited.

  • Skin samples from injection sites may help determine the type of substance injected, such as insulin. Lung tissue, approximately 2 cm cubed, sealed in an airtight container, may also have relevance in certain cases.

  • Forensic toxicology plays a vital role in the investigation of suspicious or unexplained deaths, drug-related incidents, and other forensic cases.

  • One significant aspect of this field involves the analysis of internal organs known as viscera.

Post-Mortem Sample | Toxicological Sample

The accurate collection and documentation of samples are critical in postmortem toxicology analysis. This process ensures the integrity of the samples and provides essential information for forensic investigations.

Viscera

With reference to toxicological evidence, viscera refer to the recovery of the internal organs from a deceased body for further analysis. These internal organs are divided into thoracic, abdominal, genital and cranial viscera. These organs encompass a range of vital structures, including the heart, lungs, liver, spleen, kidneys, stomach, intestines, and bladder, among others. The viscera are carefully recovered by forensic pathologist, during post-mortem and preserve these organs for subsequent toxicological analysis. The major aim of analysis of viscera is to gain insights about the presence and effects of drugs, chemicals, or toxins within the body.

The viscera are always handled with care and its collection is performed by the forensic pathologist during autopsy. Furthermore, to minimize the risk of contamination and tempering of toxicological sample, they follow a proper procedure and ethics in collection. The pathologist collects each and every organ individually and separately, therefore, to prevent any potential contamination.

Notably, for the preservation of visceral sample, each organ is meticulously stored in a separate container. Moreover, the container should be well labeled with name of deceased and with type of organ. It should contain case number, date, organ type, and other pertinent details are essential for accurate identification.

Toxicological Sample Labeling and Documentation

Every sample must be clearly labeled with the following information:

  • Name of Deceased,

  • Date of Birth,

  • the date and time of sample collection,

  • and the sample site.

It may also be appropriate to assign a post-mortem reference number to facilitate record-keeping. Additionally, the request form should be fully completed, including all relevant details of the deceased, such as

  • the circumstances of death,

  • any clinical history (including infectious disease risk),

  • available drugs,

  • and the name of the requesting Pathologist.

The labelling and documentation of viscera sample encompasses additional information, which holds prominent grounds investigations. Notably, viscera samples are very close to easily get tempered and contaminated, therefore, this information are necessary.

  • case number

  • date of collection

  • organ type

  • other pertinent details are essential for accurate identification.

Meticulous documentation throughout the collection and preservation process is imperative to maintain an unbroken chain of custody. Detailed records of the collection, packaging, sealing, and labeling of toxicological sample should be upheld, including the names and signatures of all individuals involved in each.

Preservation Methods

The choice of preservation method hinges upon the unique requirements of each case and subsequent toxicological analyses to be conducted. Three commonly employed preservation methods include refrigeration, freezing, and chemical fixation:

a. Refrigeration: Antemortem sample can be refrigerated within the temperature range of 2 to 8 degrees Celsius (36 to 46 degrees Fahrenheit). Refrigeration serves to retard microbial growth and enzymatic activity, preserving the samples for a limited period of time.

b. Freezing: Freezing viscera at temperatures below -20 degrees Celsius (-4 degrees Fahrenheit) facilitates long-term preservation, effectively impeding degradation and microbial growth. It is crucial to employ suitable containers and ensure proper insulation to prevent freezer burn or frost damage.

c. Chemical Fixation: In specific cases where histopathological analysis is necessary, the toxicological sample may undergo preservation in a fixative solution such as formalin. Chemical fixation aids in preserving tissue structure and cellular morphology, thus enabling subsequent microscopic examination.

This blog has achieved its aim to provide you insights about the collection, packaging and storage of toxicological samples.

Reference

  • "Forensic DNA Typing" by John M. Butler

  • "The Forensic Casebook: The Science of Crime Scene Investigation" by Ngaire E. Genge

  • "Forensic Science: A Very Short Introduction" by Jim Fraser

  • "Practical Crime Scene Processing and Investigation" by Ross M. Gardner