Expert opinions have a special place in proving claims because they are used as a counterpart in order to increase the judge's knowledge in identifying a specialized subject. Due to this importance, in preparing expert opinions and creating a unity of procedure, it is necessary to recognize the reasons for differences in presenting expert opinions, and after recognizing them, to take action to eliminate them, which is the mission of this important research. In terms of the purpose of this research, it is applied and in terms of method, it is descriptive-survey. A 26-item questionnaire was formed in the Likert scale. The results were first analyzed using descriptive statistics and then using SPSS software and one-sample t-test. Findings Documentary studies of this study showed that experts have the most disagreement on the issues of applying Note 3 Article 14 of the Law on Investigation of Violations, speeding intervention in the cause of total accidents, fake accidents and pedestrian accidents. Also, the results of the questionnaire were ranked using Friedman test. Weakness in equipment and technology, weakness in education and weakness in rules and regulations, respectively, are the most important reasons for differences of opinion of experts. Conclusion In order to achieve the same procedure in providing expert opinions and reducing differences, recognizing the root causes of accidents is inevitable. This will be possible by upgrading effective equipment and technologies in this field, increasing specialized training, and amending existing laws and regulations.