Detectability of the Psychotropic Substance Cannabis in Head or Body Hair: Update of Forensic Criminalistics

Abstract

Cannabis is a substance known and used by humans for thousands of years. Both from China and India, very old written traditions are known, which prove the use of cannabis in medicine. From the USA, there are opinions of scientists, who attribute a much higher risk for a lethal overdose to prescription drugs than is possible at all by the consumption of cannabis. Estimates for the area of the Federal Republic of Germany assume approximately 85,000 deaths per year due to the use of drugs and their undesirable side effects. The legal view of cannabis use is, with a few exceptions, a worldwide ban. In order to be able to implement these legal norms, investigators make use of a wide variety of procedures to prove the use of psychotropic substances in a court of law. In addition to the classical methods of taking blood samples and/or urine samples, it has also been possible for some time to prove the use of cannabis by examining hair samples. Only for about 40 years have various methods for retrospective forensic protection been available to criminalistics. Investigators use the special characteristics of hair, as opposed to blood, sperm or saliva. The hair grows more or less continuously from the root and stores substances from the metabolism of the body. This makes it possible for investigators to investigate the use of cannabis depending on the length and condition of the hair. In addition, the analytical methods for hair matrix analysis are continuously being developed. Studies have also shown various possibilities for the incorporation and accumulation of THC and its metabolites, the main active substances of cannabis, in hair. In addition to the classical substances for the preservation of evidence, further approaches result from scientific findings regarding the forensic analysis of hair. The securing and examination of head hair has become a standard procedure in investigations. It represents only a minor intervention for the test person. In addition, the storage of hair does not make any special demands on the temperature as an example. This makes hair a good examination tool for many parties involved in the procedure. However, scientific findings show the possibilities, risks and dangers of focusing exclusively on hair. In addition to the use of body hair as an object of investigation for the reliable collection of data, body hair can open up new possibilities. However, scientific findings must not be disregarded here. Every investigator must be aware at all times that he may only carry out interventions on accused persons on the basis of the respective state standards. The courts, too, can only give fair judgements if the investigating authorities have secured evidence that is also based on current scientific findings. In addition to the biological processes involved Digital Forensic Science 2 in the storage of foreign substances in the hair matrix, it is also necessary to describe in detail the various variants of analysis and evaluation on the various hair samples. All investigators must be aware at all ti...