**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

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 times that they may only intervene against accused persons on the basis of the relevant state standards. The courts, too, can only pass just sentences if the investigating authorities have secured evidence based on the latest scientific findings. In addition to the biological processes involved 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.

**Keywords:** cannabinoid, THC, forensic head/body hair analysis, scientific findings

## **1. Introduction**

The current relevance of an ever-increasing drug problem is illustrated here using the example of the Federal Republic of Germany. These data are of course not transferable one to one to every country. However, the numbers of trade and consumption of cannabis, for example, continue to rise throughout Europe [1].

According to police crime statistics, the number of trade offences involving cannabis in the Federal Republic of Germany increased by 18% between 2013 and 2017 [2]. The share of cannabis in comparison to other illegal drugs amounts to 64% and thus represents by far the largest share [3]. It should be mentioned here that crime statistics can only ever represent the so-called bright field. These are therefore only criminal acts that have become known to the police. This can be done by own investigations or by statements of witnesses. A frequently much larger proportion of criminal offences are in the dark field, are not known to the investigating authorities and are therefore not included in the statistical surveys.

The investigating authorities rely almost exclusively on the protection of head hair when securing evidence for the use of cannabis. This behaviour, which is partly voluntarily imposed or simply spread away by ignorance, disregards a large part of the securing material. In addition to the obvious hair on the head, body hair can also be secured on the arms, legs, armpits or skinned hair and used for evaluation.

However, it is also questionable to what extent hair from evidence is basically suitable for actual cannabis use?

### **2. Current status**

### **2.1 Chemical structure of cannabis**

*Cannabis sativa* L. is the Latin name for hemp [4]. In the chemical analysis of cannabis, more than 600 ingredients are already known. There are 100 cannabinoids and 50 hydrocarbons alone [5]. The dried leaves and flowers of the THC-rich cannabis varieties are called marijuana. The drug-typical THC content, which also contains psychoactivity, is between 1 and 20%. The leading cannabinoid responsible for this is the Δ9-THC [4]. The exact name of the Δ9-THC is Δ9-tetrahydrocannabinol. Due to the different numbering systems, the term Δ1-tetrahydrocannabinol is also used in part, but it names the same molecule. It is chemically C21H30O2 and has a molecular weight of 314.47 Da [6] (**Figure 1**).

Recent research methods from the Δ9-THC have also analysed the main metabolites 11-Nor-9-carboxy-delta-9-terahydrocannabinol (CTHC)/(THC-COOH) and its glucuronide (CTHC-Glu). After cannabis use, CTHC-Glu is the main excretion product that can be detected in urine. However, studies on the detection of cannabis

**119**

**Figure 3.**

*Chemical formula of THCA-A.*

**Figure 1.**

**Figure 2.**

*Chemical formula of the THC.*

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

use in urine or blood have not provided comprehensive, reliable results of actual use [7]. The metabolite of the THC, 11-Nor-9-carboxy-delta-9-terahydrocannabinol (THC-COOH), can be stored in, among other things, by the supply in the hair bulb

Another relevant stock is THCA-A (Δ9-tetrahydrocannabinolic acid A). This cannabinoid is the non-psychotoxic, biosynthetic precursor of THC and is present

Furthermore, the cannabinoids cannabinol (CBN) and cannabidiol (CBD) are also analysed in hair analysis [9]. These substances are not psychoactive and are

The forensic preservation of evidence on hair is done by an individualising examination using molecular biological methods. In this way, incorporated foreign substances can be found and secured in the hair. In large parts of jurisprudence the view is taken that in principle a consumption, but also an existing abstinence of the consumption of cannabis can be determined. Here the possibility of retrospective analysis of cannabis use is advantageous. This can also be done for the past weeks up to months [10]. This is possible by a more or less continuous growth of the hair. The human hair grows about 1 cm per month. It allows an appropriate review (depending on the length of the hair) of a possibly long period of time by storing substances absorbed by the body in the hair [11]. This area of hair growth, known as the anagen

in the hair. THC-COOH is the most important main metabolite (**Figure 2**).

in fresh plant material of the cannabis plant [8] (**Figure 3**).

*Chemical formula of 11-Nor-9-carboxy-delta-9-terahydrocannabinol (THC-COOH).*

*DOI: http://dx.doi.org/10.5772/intechopen.90881*

THC oxidation products.

**2.2 Course of hair growth**

*Detectability of the Psychotropic Substance Cannabis in Head or Body Hair: Update of Forensic… DOI: http://dx.doi.org/10.5772/intechopen.90881*

use in urine or blood have not provided comprehensive, reliable results of actual use [7]. The metabolite of the THC, 11-Nor-9-carboxy-delta-9-terahydrocannabinol (THC-COOH), can be stored in, among other things, by the supply in the hair bulb in the hair. THC-COOH is the most important main metabolite (**Figure 2**).

Another relevant stock is THCA-A (Δ9-tetrahydrocannabinolic acid A). This cannabinoid is the non-psychotoxic, biosynthetic precursor of THC and is present in fresh plant material of the cannabis plant [8] (**Figure 3**).

Furthermore, the cannabinoids cannabinol (CBN) and cannabidiol (CBD) are also analysed in hair analysis [9]. These substances are not psychoactive and are THC oxidation products.

### **2.2 Course of hair growth**

*Digital Forensic Science*

**1. Introduction**

suitable for actual cannabis use?

**2.1 Chemical structure of cannabis**

**2. Current status**

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 times that they may only intervene against accused persons on the basis of the relevant state standards. The courts, too, can only pass just sentences if the investigating authorities have secured evidence based on the latest scientific findings. In addition to the biological processes involved 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.

**Keywords:** cannabinoid, THC, forensic head/body hair analysis, scientific findings

The current relevance of an ever-increasing drug problem is illustrated here using the example of the Federal Republic of Germany. These data are of course not transferable one to one to every country. However, the numbers of trade and consumption of cannabis, for example, continue to rise throughout Europe [1]. According to police crime statistics, the number of trade offences involving cannabis in the Federal Republic of Germany increased by 18% between 2013 and 2017 [2]. The share of cannabis in comparison to other illegal drugs amounts to 64% and thus represents by far the largest share [3]. It should be mentioned here that crime statistics can only ever represent the so-called bright field. These are therefore only criminal acts that have become known to the police. This can be done by own investigations or by statements of witnesses. A frequently much larger proportion of criminal offences are in the dark field, are not known to the investigating

The investigating authorities rely almost exclusively on the protection of head hair when securing evidence for the use of cannabis. This behaviour, which is partly voluntarily imposed or simply spread away by ignorance, disregards a large part of the securing material. In addition to the obvious hair on the head, body hair can also be secured on the arms, legs, armpits or skinned hair and used for evaluation. However, it is also questionable to what extent hair from evidence is basically

*Cannabis sativa* L. is the Latin name for hemp [4]. In the chemical analysis of cannabis, more than 600 ingredients are already known. There are 100 cannabinoids and 50 hydrocarbons alone [5]. The dried leaves and flowers of the THC-rich cannabis varieties are called marijuana. The drug-typical THC content, which also contains psychoactivity, is between 1 and 20%. The leading cannabinoid responsible for this is the Δ9-THC [4]. The exact name of the Δ9-THC is Δ9-tetrahydrocannabinol. Due to the different numbering systems, the term Δ1-tetrahydrocannabinol is also used in part, but it names the same molecule. It is chemically C21H30O2 and has a molecular weight of 314.47 Da [6] (**Figure 1**).

Recent research methods from the Δ9-THC have also analysed the main metabolites 11-Nor-9-carboxy-delta-9-terahydrocannabinol (CTHC)/(THC-COOH) and its glucuronide (CTHC-Glu). After cannabis use, CTHC-Glu is the main excretion product that can be detected in urine. However, studies on the detection of cannabis

authorities and are therefore not included in the statistical surveys.

**118**

The forensic preservation of evidence on hair is done by an individualising examination using molecular biological methods. In this way, incorporated foreign substances can be found and secured in the hair. In large parts of jurisprudence the view is taken that in principle a consumption, but also an existing abstinence of the consumption of cannabis can be determined. Here the possibility of retrospective analysis of cannabis use is advantageous. This can also be done for the past weeks up to months [10]. This is possible by a more or less continuous growth of the hair. The human hair grows about 1 cm per month. It allows an appropriate review (depending on the length of the hair) of a possibly long period of time by storing substances absorbed by the body in the hair [11]. This area of hair growth, known as the anagen

**Figure 1.** *Chemical formula of the THC.*

**Figure 3.** *Chemical formula of THCA-A.*

phase, lasts about 4–6 years. About 80–95% of the hair in a healthy person is in this phase. In the second phase, the catagenic phase, cell division is stopped to form the hair. Hornification occurs. The second phase takes place over a period of 2 weeks. Only a few percent of the hair is in this stage of development at the same time. In the last, telogenic phase, the hair is already dead and is pushed out by a new hair forming in the hair root [12]. The diagram provides an overview of the structure and position of the hair root in the skin (**Figure 4**).

In the case of body hair, growth is significantly slower in a period between several months and a maximum of 1 year. The percentage of anagenic hair is only between 20 and 50% [14].

The storage of various substances, such as psychogenic substances in connection with hair growth and the associated pushing out of the hair, creates a temporal record of substance consumption in the hair in the manner of a tachograph, such as an example in a truck.
