**2.3 Storage of foreign substances**

The hair absorbs foreign substances such as psychogenic substances in various ways. On the one hand, this occurs through contact with foreign substances in the body's bloodstream, which supplies the anagen hair with nutrients during growth. Through the metabolism and structure of the hair, the drug substances enter the resulting hair and are stored there [15].

The substances THC and THC-COOH can be stored in the hair in three ways. On the one hand a passive diffusion from blood capillaries directly into the hair matrix takes place. This takes place at the basement membrane of the hair follicle. The second way is the diffusion of sweat or sebum directly into the finished hair. The last possibility is contamination from the surrounding area [16]. The decisive factor is that THC-COOH is only formed in the body [17]. This also means that only THC-COOH can be actively incorporated into the hair matrix, which can be regarded as safe proof of cannabis use. However, the exact process of incorporating THC-COOH from the body into the hair matrix has not yet been fully researched scientifically [16].

**121**

standard.

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

In addition to the storage of substances, hair also absorbs them into the hair through external contact with substances and stores them there. The keratinized hair absorbs these foreign substances/substances, for example through drugcontaining sweat, gases or dusts. The problem here is that in common laboratory practice, THC is still very often the only substance sought in the hair sample material. THC is found in a very high concentration in cannabis smoke and can lead to a strong contamination of the hair by an external build-up. The detection of THC-COOH in the laboratory is difficult and very time-consuming due to the very

In addition to this problem, very high concentrations of THCA-A (Δ9-tetrahydrocannabinolic acid A) also occur in chemical examinations of forensic hair samples [18]. THCA-A is the most important cannabinoid in fresh plant material. This substance is released, for example, by heating (smoking, baking). An uptake of THCA-A into the bloodstream could not be confirmed in earlier

The concentration of the stored substances can, however, be drastically changed

by environmental influences. The concentration is significantly reduced by the cosmetic treatment of the hair by bleaching, tinting or the form of a permanent wave [15]. The problem here is that there is no reliable data on how much the concentration decreases depending on external environmental influences. The degree of degradation can range from about 10% to almost 100% of the foreign substance [19]. Therefore, no scientifically reliable statement can currently be made as to which environmental influence causes which concentration change. These changes of the substance concentration can lead to a complete destruction of the hair substance and the foreign substances stored with it by a thermal treatment/ thermal stretching of the hair [20]. Basically it can be stated that foreign substances are stored in the hair during the formation of new hair and thus in the anagen phase and can additionally be stored in the keratinized hair through external contact. The difference, however, is that substances stored in the hair through growth fix themselves firmly in the hair matrix and then grow outwards from the hair root [14]. It takes about 10–14 days until the newly formed hair is outside the

**3.1 Police preservation of evidence of hair for the detection of cannabis**

The example of the Federal Republic of Germany shows that the investigators there use hair on the head as evidence in addition to blood or urine in accordance with the current legal situation. These should be removed in the area "above the occipital protuberance." In accordance with the national requirements, corresponding documentation obligations are prescribed for the extraction in order to be able to bring the evidence into the criminal proceedings in a legally secure manner and

Here again a central problem of the investigating authorities becomes apparent. Scientific findings are often only implemented or amended after a very long period of time. As a result, case law and police investigations lag behind scientific progress. This leads in large parts to a frequently delayed, fairer jurisdiction, since evidence is used in court which already no longer corresponds to the current scientific

Closer cooperation between legislators, investigating authorities and researchers

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

low dose [16].

studies [8].

scalp [21].

**3. Legal regulations**

ultimately present it as evidence in court.

is urgently needed to improve the law.

**Figure 4.** *Structure of the hair root in the skin [13].*

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

In addition to the storage of substances, hair also absorbs them into the hair through external contact with substances and stores them there. The keratinized hair absorbs these foreign substances/substances, for example through drugcontaining sweat, gases or dusts. The problem here is that in common laboratory practice, THC is still very often the only substance sought in the hair sample material. THC is found in a very high concentration in cannabis smoke and can lead to a strong contamination of the hair by an external build-up. The detection of THC-COOH in the laboratory is difficult and very time-consuming due to the very low dose [16].

In addition to this problem, very high concentrations of THCA-A (Δ9-tetrahydrocannabinolic acid A) also occur in chemical examinations of forensic hair samples [18]. THCA-A is the most important cannabinoid in fresh plant material. This substance is released, for example, by heating (smoking, baking). An uptake of THCA-A into the bloodstream could not be confirmed in earlier studies [8].

The concentration of the stored substances can, however, be drastically changed by environmental influences. The concentration is significantly reduced by the cosmetic treatment of the hair by bleaching, tinting or the form of a permanent wave [15]. The problem here is that there is no reliable data on how much the concentration decreases depending on external environmental influences. The degree of degradation can range from about 10% to almost 100% of the foreign substance [19]. Therefore, no scientifically reliable statement can currently be made as to which environmental influence causes which concentration change. These changes of the substance concentration can lead to a complete destruction of the hair substance and the foreign substances stored with it by a thermal treatment/ thermal stretching of the hair [20]. Basically it can be stated that foreign substances are stored in the hair during the formation of new hair and thus in the anagen phase and can additionally be stored in the keratinized hair through external contact.

The difference, however, is that substances stored in the hair through growth fix themselves firmly in the hair matrix and then grow outwards from the hair root [14]. It takes about 10–14 days until the newly formed hair is outside the scalp [21].

### **3. Legal regulations**

*Digital Forensic Science*

between 20 and 50% [14].

an example in a truck.

**2.3 Storage of foreign substances**

resulting hair and are stored there [15].

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

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

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

The hair absorbs foreign substances such as psychogenic substances in various ways. On the one hand, this occurs through contact with foreign substances in the body's bloodstream, which supplies the anagen hair with nutrients during growth. Through the metabolism and structure of the hair, the drug substances enter the

The substances THC and THC-COOH can be stored in the hair in three ways. On the one hand a passive diffusion from blood capillaries directly into the hair matrix takes place. This takes place at the basement membrane of the hair follicle. The second way is the diffusion of sweat or sebum directly into the finished hair. The last possibility is contamination from the surrounding area [16]. The decisive factor is that THC-COOH is only formed in the body [17]. This also means that only THC-COOH can be actively incorporated into the hair matrix, which can be regarded as safe proof of cannabis use. However, the exact process of incorporating THC-COOH from the body into the hair matrix has not yet been fully researched scientifically [16].

and position of the hair root in the skin (**Figure 4**).

**120**

**Figure 4.**

*Structure of the hair root in the skin [13].*

### **3.1 Police preservation of evidence of hair for the detection of cannabis**

The example of the Federal Republic of Germany shows that the investigators there use hair on the head as evidence in addition to blood or urine in accordance with the current legal situation. These should be removed in the area "above the occipital protuberance." In accordance with the national requirements, corresponding documentation obligations are prescribed for the extraction in order to be able to bring the evidence into the criminal proceedings in a legally secure manner and ultimately present it as evidence in court.

Here again a central problem of the investigating authorities becomes apparent. Scientific findings are often only implemented or amended after a very long period of time. As a result, case law and police investigations lag behind scientific progress. This leads in large parts to a frequently delayed, fairer jurisdiction, since evidence is used in court which already no longer corresponds to the current scientific standard.

Closer cooperation between legislators, investigating authorities and researchers is urgently needed to improve the law.
