Criminal investigation is the process of conducting research and examinations in order to identify the perpetrator and uncover the details of a crime. When successfully completed, this process clarifies the suspicious incident, leading to the identification and punishment of the individual or individuals responsible for the crime. Additionally, it helps prevent potential future crimes by restricting direct contact between the perpetrator and civilians or society. In the initial stages of a criminal investigation, the crime scene is secured, and potential evidence that could aid in solving the case is preserved by the investigative teams. Testimonies from witnesses and evidence left behind by the perpetrator are collected at the scene to shed light on the incident. The collected evidence is then subjected to various scientific examinations within the scope of forensic sciences by experts specialized in different fields, employing scientific tools and methods. As a result of these scientific examinations, the identity of the perpetrator can be determined, and the crime can be substantiated. The main objective of criminal investigation is to use scientific methods to identify the actual crime and the criminal.

When a criminal incident occurs, all stages of the criminal investigation, from the police securing the crime scene to evaluating the evidence and presenting it to the judiciary, fall under the scope of criminal investigation. All these stages should be meticulously completed following proper procedures.

Criminal cases can arise in various contexts. Apart from physical crimes that result in death or injury, there are also scientific crimes and various offenses such as document forgery and theft. The investigation of the crime depends on the area in which it was committed. Following this, investigators analyze data related to cybercrimes, such as correspondence, images, audio, camera recordings, data collected from cell towers, and computers. For document forgery, handwriting and signature examinations are conducted, and the authenticity of the document is verified by relevant institutions after the examinations. In traffic accidents, damage and fault determinations are made, records are collected, and license plate identifications are conducted. Ballistic investigations are carried out, especially in cases of murder and assault. After examining the evidence collected, ballistic examinations determine the type of weapon and ammunition used. In the case of financial crimes, examinations are conducted to detect fraud, such as analyzing bank account activities, to prove the crime. Tax offenses are also investigated as part of financial crimes, and relevant examinations are carried out.

In summary, criminal investigation involves a comprehensive process that uses scientific methods and various forensic disciplines to identify criminals and substantiate crimes. This process plays a crucial role in safeguarding public safety and ensuring that justice is served.