**Author details**

*Digital Forensic Science*

tion (**Figure 5**).

a way of obtaining legally certain evidence.

*Incorporation of THC, THCA-A and THC-COOH into the hair.*

criminal proceedings. The investigating authorities, using the example of the Federal Republic of Germany, have regulated the preservation of evidence for hair samples by means of ordinances. The occipital protuberance is explicitly named as the sampling point. This restriction of the sample location represents a clear restriction for an optimal preservation of evidence for the proof of cannabis use. The latest research results have shown that it is possible in a very complex laboratory procedure to extract and analyse only the THC-COOH content from the hair sample material, which was also incorporated into the hair matrix via the hair root and thus by the test person's body. Unfortunately, the research situation is still very low. There are still justified doubts whether the THC-COOH is incorporated into the hair matrix exclusively via the blood circulation or whether another way of contamination with THC or its metabolites is possible. The use of cannabis is only recorded in brightfield by police crime statistics. It is increasing successively and has become a mass crime. The possibility of an efficient investigation should therefore be used. THC accumulates on the hair, especially during inhaled consumption, due to the development of smoke. Studies have shown that, in addition to the adhesion by cannabis smoke, the inhalation into the hair can also occur through contact with sweat, fresh plant material and other surfaces. Both head hair and body hair are affected. The contamination pathways of THC, THC-COOH and THCA-A have been shown in various studies. This is illustrated again in the following diagram. Also the ways are represented, which are not yet finally clarified due to the current research situa-

In order to continue to use hair analysis as safe evidence in criminal proceedings,

Investigation authorities have a neutral legal mandate to secure, evaluate and analyse all incriminating and, in particular, exculpatory evidence. The current findings with regard to the analysis of head hair or body hair do not currently

extensive studies should first be carried out to gain more insight into the actual route of enrichment and contamination of cannabis and its metabolites. The current state of scientific knowledge raises more questions than it can answer in relation to hair analysis. If, as an example, it continues to be confirmed that THC-COOH integrates into the hair matrix via the bloodstream after consumption, this would be

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**Figure 5.**

Thorsten Floren M.A. University of Police and Public Administration (HSPV NRW), Germany

\*Address all correspondence to: thorsten.floren@web.de

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
