Investigative experts use tactics developed in criminology and applied in practice by employees of investigative institutions, influencing the position of the interrogated person in order to obtain truthful testimony from the participants in the criminal case, which is known from information related to the criminal incident. The information provided by the investigating expert is statements that the investigating expert must register in accordance with the law, so that subsequent statements can be used as required evidence in a criminal case.

The use of interrogation tactics is most effective in obtaining accurate information about the circumstances in which the suspect or accused person committed a criminal act, for example, in case of forgetfulness of information about the subject of interrogation or refutation of the results of the investigation, this is manifested in the refusal to provide evidence or the desire to distort information about the crime, information about your behavior.

Differentiated grounds for tactical methods of interrogation are set out in scientific works by forensic authors [1, p. 273].

The professionalism of an expert depends on competence and conscientiousness. The correct choice of tactics during the preliminary investigation testifies to the special status of expert research. A possible reason for the review of the case could be the lack of motivation to approve the expert opinion. During the consideration of the case, which again returned to the court, the employees strove to be competent in their work.

In the work of an expert during a trial, it is necessary to compare the exact chain of investigation, which should determine the truth of the criminal case. Wrong tactics in expert interrogations will lead to conflicting conclusions, which will cause problems for the decision of the court and will be ignored. After that, the work of investigating experts will be devalued.

During the interrogation of an expert, if there are deliberately false conclusions, the person will try to oppose the investigator. As for deliberately incorrect conclusions, the expert is liable under Article 307 of the Criminal Code of the Russian Federation, and if ignorance of the investigative actions arising from the subject of interrogation is revealed, he changes the psychological component of the interrogation and the facts of tactical and structural examination may include incorrect statements, as well as incorrect interpretations , which lead to inconsistencies in the conclusions and major errors in the work of the expert.

The effectiveness of the interrogation undoubtedly depends on the professional knowledge, qualities, as well as on the experience of the investigator [3, p. 209]. The purpose of the investigative action in the trial is to obtain explanations and conclusions. Information provided to an expert may also be the subject of an expert’s request. To explain this conclusion, the expert explained the need to use the chosen research method and explained the wording and terminology of the indications. And often the lack of desire to develop the limits of expert research, the appointment of expertise developed by investigators, the content of questions of a formal nature is psychologically natural for experts. Opponents with basic tactics and professional skills face investigators in the process of interrogating experts. The investigator is incompetent in the process of interrogation in the field of expert knowledge, therefore the expert has a subjective attitude towards the investigator [4, p. 198].

Investigative interrogation in the presence of an expert, his tactics:

1. If the protocol of the testimony received contains the questions of the investigator and the answers of the expert, then these evidence will not be withdrawn by the judge from the evidence base. It will not be difficult for a professional specialist to use the questions of a law enforcement officer, in which typical linguistic turns are used that do not have terminological overload. The testimonies received and the questions raised are recorded in the protocol by the investigator.
2. Changes are made to the definitions of the investigator, which are interpreted by the expert. The terminology used by the examiner must be justified in order to fully understand and explain the work performed.
3. In the process of interrogating an expert, the main rule is not to make a mistake that may affect his future clients, and as a result will be considered by the leadership of the expert institution. The expert uses the specific terminology used to formulate the answer.
4. Unfavorable perception on the part of the specialist will be a serious result. If the transfer approval information is incorrect, the investigating expert may refuse to sign the protocol. Questions considered by the expert and specialist take up most of the time. For a clear perception of the issues of scientific discussion, the direction of clarity and meaningfulness is objectively implied. A conversation of experts in which an incompetent investigator tries to intervene can make himself look reprehensible.
5. If questions still remain before the expert, then the tactics of the investigating expert are repeated. The results of the statement by the investigator are recorded in the protocol of the interrogation of the expert [5, p. 367].

In order to change the dishonest behavior of the accused (suspect), who, as a rule, give false testimony or have the intention to refuse to testify, psychological contact must be established in order to ease anxiety, excitement, tension, suspicion, anxiety, hostility, anxiety, that is, the creation prerequisites for the readiness of the interrogated to communicate with the interrogator.

It was noted that the use of the following tactics contributes to psychological contact between the interrogated and the investigating expert: the technique of «psychological stroking», the rule of «accumulation of consent, demonstrating common interests, assessments, views (for example, the investigating expert shows interest in the interrogated person doing a certain sport).

The most effective tactics for dealing with an interrogated investigative expert and disclosing false testimony are considered to be the use of contradictions between his testimony and other elements of the case, the sudden nature of the problem or the presentation of evidence, the combination of evidence techniques involving legends and details, inertia, distractions, an idea, etc. [2, p. 84].

Based on the foregoing, we can conclude that in a criminal case interrogation is one of the most difficult forms of establishing the truth. The decision of the expert has a real value when creating a situation in which the court ignores all other evidence, if it contradicts the subject of proof, as a result of which, during the judicial investigation, devalues ​​the work of the investigating expert.