The paper addressed the following questions: how can AI be applied in corporate internal investigations and what are the legal limits for its use? In case of effective application, how can it affect the admissibility and valuation of the information collected from these procedures in an eventual criminal lawsuit? It was demonstrated that, with the expectation of increasing the effectiveness and efficiency of compliance programs, AI has been used in real-time – and often predictive – supervision of employees, as well as in carrying out internal investigations, through, for example, lie detection systems. However, due to the limitations and risks of this technology, its employment must comply with legal parameters and restrictions. Therefore, three categories of restrictions were analyzed: with respect to (i) legal requirements for data processing, we noted that the processing of data to be used as input in those systems must find legal support in one of the hypotheses provided for in Articles 6 and 9(2) of the GDPR. Furthermore, the fundamental principles that substantiate the test of proportionality between the intended purpose and the intervention to be carried out, provided for in Article 5, must be observed. Regarding (ii) possible prohibitions on the use of AI systems in the context of internal investigations, we observed that the use of technologies to control and supervise the work environment must take into account the requirements of legality, shall not affect areas in which employees’ expectations of privacy must prevail, and, lastly, must observe a second test of proportionality, aimed at assessing whether the technology in question is adequate and necessary to achieve the purpose intended with it and whether the rights possibly affected by it should not prevail. About the (iii) limits to the admissibility and valuation of elements of information from internal investigations, we concluded that their admission in criminal proceedings will depend on a new judgment of legality and proportionality. In addition, they may be admitted when presented by the company, in its defence, or by Public Prosecution, provided that a third test of proportionality is observed and that these elements of information are not considered sufficient to substantiate the conviction of any defendant, therefore having probative value similar to elements from state investigation acts.