Parental intoxication: A scientific diagnostic approach in classifying parental substance misuse

December 1st, 2021

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Alcohol and drug abuse are omnipresent in South Africa (SA). The United Nations Office of Drugs and Crime (UNODC) claims that 22 million people in Africa between the ages of 15 to 64 years used drugs in 2018 (UNODC World Drug Report 2021, booklet 2, Global Overview of Drug Demand and Drug Supply (, accessed 15-11-2021)). This figure is forecast to escalate as Africa is predicted to have the most significant population growth in the world during the next decade.

Substance abuse is known to distort an individual’s social functioning, therefore, the percentage of individuals abusing alcohol and drugs, ending up in parental rights and responsibilities disputes, is becoming higher. Inappropriate substance use by parents is often also a contributing factor to these disputes. The percentage of investigations related to drug and alcohol abuse in parental responsibilities and rights disputes by the Office of the Family Advocate is on the rise.

The substances used by parents include legal substances, such as alcohol and cannabis, and illegal substances, such as methamphetamine (TIK), cocaine and heroin. Parents also misuse prescription and over-the-counter medications, all of which can impact their ability to exercise their parental responsibilities and rights responsibly. It is essential to keep in mind that some legitimate cannabidiol oils (CBD oil) may be contaminated with Tetrahydrocannabinol (THC), the psychoactive substance of cannabis.

This article focuses on detecting inappropriate drug and alcohol use in parental rights and responsibilities cases where allegations of substance misuse are investigated. The outcome of these investigations often disqualifies parents from having contact with their children or limits rights and responsibilities regarding decision making.

The trend in current-day SA to classify an individual’s substance use as inappropriate or problematic is to –

  • perform screening tests for drugs (without confirmation) and liver enzyme induction tests for alcohol use;
  • use the nominal values of test results (without taking the significance of a test into account); and
  • make a decision about the parent’s substance use habits, which may restrict their parental rights and responsibilities severely.

I submit that the abovementioned approach is incorrect and suggests that a rational, scientifically correct ‘diagnostic’ approach must be followed when classifying an individual as a problematic substance user. The analytical test results must form part of the diagnostic paradigm instead of a limited threshold approach for safety-sensitive environments where only the cut-off concentration is used to make a decision. Additional information like medical history, social function, and others must also be considered when making a rational decision in these cases.

The medical-legal questions raised must be viewed at an integrative level with a multi-layered approach, founded in the supreme provisions of the Constitution, relevant legislation, considerations of medical ethics and international due scientific practice.

Legislative framework

  • Constitutional rights: The right to privacy, freedom, autonomy, freedom of religion, children’s rights, the equal enjoyment of rights and privileges, and the limitation thereof are prescribed in the Bill of Rights of the Constitution.
  • Legislation: Sections 7, 9, 24 and 28 of the Children’s Act 38 of 2005 determines that the High Court is the guardian of all children and will pronounce on the ‘child’s best interest’ standard. This standard applies to parental responsibilities and rights cases where the parents misuse substances, which often disqualify them from having contact or care of their children and often limits their parental responsibilities and rights.
  • Medical ethics: The overall assessment aims not to have a purely clinical diagnostic purpose but rather to classify an individual as an inappropriate drug or alcohol user. It is essential to keep in mind that analytical testing is still a biomedical intervention on a human. This necessitates an ethical and legal approach similar to the medical profession’s regarding fundamental human rights, as prescribed by the Health Professions Council of South Africa (HPCSA). It highlights the general sensitivity in the medical law environment to respect privacy, dignity, and bodily integrity.

The legal fraternity is well versed in the legal aspects of these cases, however, detailed knowledge of scientific and legally defensible testing protocols is often not part of their knowledge base.

Legally defensible testing protocol

A sampling of biological matrices must be performed by an individual trained and registered at the HPCSA within the required field of expertise. Voluntary informed autonomous consent is required for all biomedical testing. The parent may designate a specific individual whom they deem suitable to receive the test reports or themselves only.

The sampling officer must request photographic identification and take a photo of the individual at the time of specimen collection. Anonymous submission of hair samples by courier is not ethically correct since the owner of the hair sample must provide consent.

The specimen must be collected and stored to preserve the sample’s integrity before shipping to the confirmation laboratory for testing. The chain-of-custody must also be documented.

The test results must be kept confidential and communicated on a need to know basis only, with the explicit permission of the parent or on a court order.

Medical-scientific framework

  • Markers of exposure and effect: Drug use is detected with markers of exposure, which refer to parts of the initial parent compound present in the human body after consumption. A marker of effect indicates the effect of the drug or alcohol on the body. A typical example of effect markers is the liver enzymes such as Gamma-Glutamyl Transferase (GGT) and carbohydrate-deficient transferrin (CDT) induced with regular alcohol use.

The testing protocol should involve detecting the substance with a marker of exposure first. An assessment of the amount of the substance consumed can then be done by employing a marker of effect as corroborating evidence. In the ideal case, the exposure and effect markers are identical – such markers are available for alcohol in hair.

The applicability of the matrices such as blood, urine or hair also needs to be appreciated.

Drugs and alcohol are present in the blood for a few hours, during which it is metabolised and become detectable in urine for a few days.

  • Hair testing: Hair is an ideal matrice to access an individual’s drug-taking habits. Drugs and alcohol, and their metabolites, are taken up in the hair since it is in continuous contact with the blood. Hair analysis provides a history of the individual’s drug use. The hair grows at approximately one centimetre per month, allowing for profiling a person’s drug consumption over time with segmental analysis.
  • Analytical testing: Threshold testing for safety-sensitive environments such as workplaces usually requires screening and confirmation tests for all non-negative specimens. Screening analyses use immunoassay technology to detect above a safety threshold concentration for the drug in urine. The immune bodies employed in immunoassay screening tests are also well known to be susceptible to cross-reactivity by other substances from the individual’s diet, prescription and over-the-counter medication, among others. Therefore, screening test results cannot be accepted as reliable evidence in any forum or court where decisive action is taken and important, far-reaching decisions are made.

Confirmation analysis, with a forensically acceptable technique such as gas chromatography-mass spectrometry (GC-MS), will eliminate the uncertainty about the identity and concentration of the substance under investigation. Confirmation tests have limits of detection (LOD) that are significantly lower than screening tests and, therefore, more suitable to detect traces of drugs that are lower than the relatively high cut-off concentrations for risk-sensitive environments. The presence of a substance at a low concentration may also indicate risky behaviour by a parent. Confirmation analytical techniques are also not limited by the number of drugs that can be detected for screening tests.

Given the gravity of the decisions in parental rights and responsibilities disputes, I submit that screening tests do not have a purpose in these cases.

  • Significance of a test: All test results must be interpreted with their significance in mind. Analytical sensitivity is the ability of a test to identify a substance in the specific matrice correctly, and analytical specificity refers to the ability to identify the absence of a drug correctly.

The analytical sensitivity and specificity of immunoassay screening tests are typically in the order of 60% to 80%. Analytical sensitivity of 70% will imply that 30% of replicate readings on the same person will not indicate the presence of a drug above the safety threshold concentration on the same specimen – 30% false-negative (FN) rate. It follows that an analytical specificity of 80% implies an incorrect detection of a drug in 20% of the replicate readings on the same person – 20% false positive (FP) rate.

Screening test results should be regarded as preliminary only. They cannot be offered as reliable evidence in any court due to their susceptibility to interferences and uncertainty in the drug concentration estimate. It is also important to note that although some screening tests are laboratory-based and performed with auto analysers on hair, blood and urine, they have the same limitations as the devices for on-site screening.

The analytical sensitivity and specificity of forensically acceptable confirmation techniques are in the order of 99, 5% for well-validated protocols operated by well qualified forensic scientists.

  • Markers of effect: The typical markers of effect employed to detect inappropriate alcohol use are the liver enzymes: Alanine aminotransferase (ALT); aspartate aminotransferase (AST); GGT and CDT. These enzymes are widely used to detect chronic alcohol use, however, they also have an associated diagnostic sensitivity and specificity, which must be considered when interpreting these pathology reports. Table 1 (below) indicates the diagnostic sensitivity and specificity for markers of effect when employed to identify chronic excessive drinking (Hilke Andresen-Streichert, Alexander Müller, Alexander Glahn, Gisela Skopp and Martina Sterneck ‘Alcohol Biomarkers in Clinical and Forensic Contexts’ (2018) Deutsches Ärzteblatt International 309).

Markers of effect (liver enzyme induction)

Marker Diagnostic sensitivity Diagnostic specificity
CDT 46 – 90% 70 – 100%
GGT 37 – 95% 18 – 93%
AST 25 – 60% 47 – 68%
ALT 15 – 40% 50 – 57%
Mean corpuscular volume (MCV) (anatomical changes) 40 – 50% 80 – 90%



88% 95%

Marker of exposure

EtGluc (hair)

Chronic excessive drinking

Cut-off = 30 Pico gram/mg hair

75% 96%
TABLE 1: Biomarkers of effect and exposure and effect for chronic excessive alcohol use. Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Carbohydrate-deficient transferrin (CDT), Mean red blood cell volume (MCV), Ethyl glucuronate (EtGluc).


In general, the diagnostic sensitivity of these effect markers for identifying chronic excessive alcohol use is not as good as the diagnostic specificity. The combination of the three effect markers CDT, MCV and GGT, has an 88% diagnostic sensitivity and 95% specificity.

These markers may also be elevated by medical disorders, which may cause FP test results, such as liver disease, genetic variations and vitamin deficiencies, among others.


  • Result interpretation: The landmark Daubert case (Daubert v Merrell Dow Pharmaceuticals Inc 509 US 579 (1993)) in the US Supreme Court in 1993 highlighted that the admissibility of scientific evidence, among others, depends on its known or ‘potential rate of error’. No scientific conclusions can be made and reported without considering a rationally obtained sensitivity and specificity. FP and FN results have a severe influence on justice. It is essential not to use test results nominally only by comparing the numerical value of the test result with the clinical normal reference range.

It is also of prime importance not to base a decision on parents’ fitness to exercise their parental rights and responsibilities regarding their children on a medical test report only. Additional information must also be considered, such as a complete review of all history, including medical, psychiatric information, social functioning, and standardised instruments such as the Michigan Alcoholism Screening Test when alcohol abuse is investigated.

Performing a screening test only, without confirmation analysis, may be viewed as a prima facie transgression of medical ethics (in the context of the regulatory role of the HPCSA). It may also be considered a form of medical malpractice (in terms of possible civil or criminal litigation). Confirmation analysis is the best practice since the identity and concentration of the substance is confirmed, eliminating the analytical uncertainty. Screening test results should not be presented as reliable evidence in any court.

Dr Johannes B Laurens BSc (Ed) BSc (Hons) MSc (Chem) MSc (Appl Tox) (Surrey, UK) MPhil (Med Law & Ethics) PhD (Chem) PhD (Med Law) (UP) is a Director/Forensic Toxicologist at Expert Laboratory Services Pty Ltd in Pretoria and Chris Maree BCom (Law) LLB (UJ) is the Senior Family Advocate and Head of the Pretoria Office of the Family Advocate at the Department of Justice and Correctional Servies in Pretoria.

This article was first published in De Rebus in 2021 (Dec) DR 19.

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