*4.3.2 The activity of the toxicology laboratory for forensic purposes*

When the presence of drugs is confirmed in oral fluid, the person under investigation may request the counter-analysis of another aliquot (B) of the saliva sample. This second test can be performed at the same laboratory that analysed the first aliquot (A) of the saliva sample or at another laboratory chosen by the subject in question. Aliquot B must be accompanied by a chain of custody form and include information regarding the results of the original analysis and the cut-offs used. Any laboratory that conducts analysis on aliquot B of the saliva sample must have documentation to demonstrate the use of validated analysis methodologies that meet the precision and accuracy criteria appropriate to the required analyses. It is crucial to guarantee the chain of custody [55], a documented procedure designed to ensure the authenticity, integrity and traceability of a sample from the moment of collection to its disposal. Following the proper chain of custody protocol is fundamental in the reconstruction process and ensures that the sample can be located at any point, unequivocally identified, stored correctly under the right conditions, and protected from tampering and voluntary or involuntary adulterations in all phases. Documentation of the chain of custody must also record every movement and manipulation of the sample, on which dates and under whose care. In the judicial field, the chain of custody is deemed broken in any of the following scenarios (these shortcomings will lead to dispute and may even constitte instances of mystification):


On the basis of what has been said thus far, it is evident that laboratory staff are required to fulfil many responsibilities, with potential repercussions in the forensic field in the event of proven professional malpractice. It is therefore necessary to:


**151**

*Salivary Analysis for Medico-Legal and Forensic Toxicological Purposes*

Standard Operating Procedures (SOP) manual;

• provide the personnel of the laboratory with access to the complete, updated

• maintain an internal quality control programme which ensures that the analyses are performed correctly and that the results of the tests are communicated in

• participate in appropriate External Quality Assessment (EQA) schemes;

• maintain acceptable analytical performance for all analysis methodologies

• guarantee and document the validity, reliability, accuracy, precision and performance characteristics of each analysis and each analysis system;

• ensure that the necessary corrective actions are taken to maintain laboratory operation and performance at satisfactory levels (e.g. when a quality control system indicates non-compliance with performance specifications, or in response to errors in reporting results or in the analysis of the results of an EQA); the analytical results must not be reported until all the appropriate

In this context, the forensic toxicologist clearly has a fundamental role, with the responsibility of interpreting the analytical results of tests for substances of abuse in oral fluid at the request of a Legal Authority, competent doctor, potential customer

Oral fluid testing for drugs of abuse offers significant advantages. A saliva sample can be collected under direct observation with reduced risk of adulteration and substitution and in a less embarrassing or unpleasant manner than urine or blood collection. As oral fluid collection is non-invasive, most people find the procedure more acceptable than having to provide other biological matrices, and suitable hygiene conditions can be respected while the donor is under the collector's

By providing an estimate of the actual circulating amount, the measurement of a drug concentration in oral fluid can be used for the determination of intoxication. In fact, measurements of oral fluid drug concentrations will usually be of value only if they accurately reflect the plasma level. Therefore, before designing a useful model for the salivary secretion of drugs, it is necessary to constantly update information about the relationship between the saliva concentration level of each drug and its plasma concentration level, the mechanisms by which drugs enter oral fluid, and also the effect on salivary flow rate, production in the salivary glands, and the

It is very useful to know the limitations and possibilities of salivary analysis in forensic and diagnostic fields. Standardisation of the conditions for collection of oral fluid is strictly essential for achieving reliability and interpretation of the data. Furthermore, appropriate cut-off concentrations need to be established in the development of guidelines for oral fluid testing [56]. In future research, the mechanisms by which drugs enter the saliva must be clarified more adequately.

*DOI: http://dx.doi.org/10.5772/intechopen.95625*

compliance with SOPs;

applied in the laboratory;

corrective actions have been taken.

or designated expert representative.

nature of any protein binding in the saliva.

**5. Conclusion**

observation.

• assure the competence of laboratory staff, document in-service training, validate the analytical method, and re-evaluate work performance;


In this context, the forensic toxicologist clearly has a fundamental role, with the responsibility of interpreting the analytical results of tests for substances of abuse in oral fluid at the request of a Legal Authority, competent doctor, potential customer or designated expert representative.
