The preliminary investigation is the judicial stage that aims to uncover the truth in the criminal case, and search for all the important and necessary evidence in order to determine the validity of presenting the matter to the judiciary. It has two meanings, the first is linguistic and the second is terminological.

There have been many definitions regarding investigation. It is the collection of criminal investigation procedures that the criminal investigator undertakes when a crime or accident occurs in order to find out the truth. It is the science that clarifies to the investigator the features and guides him on how to research and proceed in collecting evidence and investigation.

Then he begins his procedures from the first procedure he comes to, and it is a group of legitimate procedures that the investigator resorts to in order to uncover the facts in the mystery of the crime in terms of knowing the perpetrators of it, the reason for committing it, how it was committed, and the place and time of its commission, and this is equivalent to him carrying out these procedures himself or with the help of With others in order to carry it out, the investigation is a set of procedures undertaken by the authority in the manner determined by the law.