Background: In specific criminal law, security crimes are of special importance for the whole society and the country due to their harmful effects on the public. One of these cases is the study of evidence in crimes against security that the manner and method of detection and investigation of perpetrators of crimes against security is different from other crimes. The purpose of explaining the cases of restriction and deviation from the principles of moral and criminal law in the way of studying the cause of crimes against security based on expediency.
Conclusion: The results of this study show that according to the emphasis of the legislator on the necessity of obtaining evidence, through legal and legitimate means in all crimes, including crimes against security, for reasons such as; expediency, urgency, the need to maintain order and security of society, bad choice from worse, etc. officers and judicial authorities can discover the reasons for committing a crime for which there is strong and convincing evidence that it has been committed and establish justice, regulation and security in society. In responding to these crimes and in the challenge between sovereignty and civil rights, governments usually take steps to guarantee sovereignty (ie, their own rights), and in this regard, as mentioned earlier, sometimes they deviate from the general and accepted principles of moral and criminal law.