A criminal investigation in Turkey does not begin only when someone is arrested or when a prosecutor files an indictment. Under Turkish criminal procedure, the investigation phase starts much earlier, at the moment the public prosecutor learns of a fact pattern that creates the impression a crime may have been committed. That early threshold matters because Turkish law is built around the idea that the prosecutor must react quickly, gather evidence lawfully, protect the rights of the suspect, and decide whether the file should end with non-prosecution, diversion, or a formal indictment. In practice, this means the beginning of a criminal case in Turkey is not a single dramatic event. It is a legal process triggered by notice, complaint, police reporting, or prosecutorial awareness of potentially criminal facts.
Understanding how criminal investigations start in Turkey is essential for anyone dealing with Turkish criminal law, whether as a complainant, suspect, victim, lawyer, or business operating in the country. The Turkish system assigns a central role to the Chief Public Prosecutor’s Office, but it also allows the first procedural trigger to come from many different directions: a private complaint, a police report, an administrative referral, a court transmission, or even information received through a Turkish embassy or consulate for offenses committed abroad but prosecutable in Turkey. The start of the investigation phase therefore depends less on a rigid filing form and more on whether legally relevant information has reached the authorities in a manner recognized by law.
The Constitutional Background
The legal starting point is the Constitution. Article 36 guarantees the right to a fair trial through legitimate means and procedures. Article 38 protects the presumption of innocence, the privilege against self-incrimination, and the rule that findings obtained through illegal methods cannot be considered evidence. Article 40 requires the State to provide prompt access to competent authorities where constitutional rights have been violated and obliges public authorities to indicate the available remedies, competent authorities, and deadlines. These provisions matter even at the very start of an investigation because they shape how the authorities may collect evidence, question suspects, and structure remedies from the first procedural step onward. (Anayasa Mahkemesi)
In other words, the Turkish investigation phase is not simply a police information-gathering stage outside constitutional control. It is already part of the criminal justice process governed by legality, fair-trial standards, and evidentiary rules. That is why the beginning of a criminal investigation in Turkey is legally significant: once the authorities move from raw information to formal investigative action, constitutional and statutory safeguards begin to apply in a meaningful way. (Anayasa Mahkemesi)
The Core Rule: The Prosecutor Acts Once an Offense Impression Appears
The central rule appears in Article 160 of the Code of Criminal Procedure. That provision states that when the public prosecutor learns, through a complaint or in any other way, of a situation giving the impression that a crime has been committed, the prosecutor must immediately start investigating the truth in order to decide whether there is room to bring a public prosecution. The same article also imposes a balanced duty on the prosecutor: for the purpose of discovering the material truth and ensuring a fair trial, the prosecutor must collect and preserve both incriminating and exculpatory evidence through the judicial police and must protect the suspect’s rights.
This article is one of the most important provisions in Turkish criminal procedure because it answers a basic question directly: a criminal investigation starts not when guilt is already proven, but when the prosecutor learns of circumstances creating the appearance or impression of an offense. The threshold is therefore lower than proof and even lower than the later “sufficient suspicion” standard required for an indictment. But the rule is not one-sided. The prosecutor’s job from the first moment is not simply to build a case against the suspect. The prosecutor must also gather evidence in the suspect’s favor and protect defense rights. That is a defining structural feature of Turkish criminal investigations.
How the Authorities Learn About a Crime
Article 158 explains how the information reaches the criminal justice system. Under that article, a notice or complaint concerning a crime may be made to the Chief Public Prosecutor’s Office or to law-enforcement authorities. If the notice or complaint is filed with the governor’s office, district governor’s office, or a court, it must be sent to the relevant Chief Public Prosecutor’s Office. For offenses committed abroad but prosecutable in Turkey, a notice or complaint may also be made to Turkish embassies or consulates.
This means the opening of a criminal investigation in Turkey is deliberately accessible. The law does not require ordinary citizens to know the precise procedural route in advance. A person who reports a crime to the police, to the prosecutor, or even to certain other public authorities still sets the machinery in motion, because the law requires those institutions to channel the matter to the correct prosecutorial office. From a practical standpoint, this is one reason many investigations in Turkey begin very quickly after an allegation is made: the procedural system is designed to move information toward the prosecutor rather than rejecting it for technical filing mistakes.
Complaint, Notice, and Ex Officio Awareness
Turkish criminal investigations may start through a victim’s complaint, a third-party notice, or ex officio awareness by the authorities. Article 160 expressly says the prosecutor acts upon learning of an offense impression “through a complaint or in any other way,” which means a formal complaint is not the only trigger. Some offenses in Turkish law are complaint-based in practice, while others are prosecuted ex officio, but in either case the prosecutor’s duty to assess the legal situation begins once legally relevant information arrives. Article 253 also shows the continuing importance of complaint-based offenses in Turkish criminal procedure by providing that mediation must be attempted for offenses whose investigation and prosecution depend on complaint, as well as for certain specifically listed offenses.
This distinction matters because people often assume that criminal investigations in Turkey start only if the victim personally files a complaint. That is not accurate as a general rule. Many files begin because the police observe conduct directly, because another public body sends information to the prosecutor, because a hospital or official reports a suspicious event, or because the prosecution learns of the matter by another lawful route. The role of complaint is important, but it is only one entry point into the system.
The Public Prosecutor’s Central Role
Once the file reaches the prosecution office, Article 161 gives the prosecutor broad investigative authority. The prosecutor may carry out any investigation directly or through the judicial police and may request all kinds of information from public officials to reach the result described in Article 160. The same provision also requires judicial police officers to inform the prosecutor immediately of events they have handled, persons apprehended, and measures applied.
This confirms that the Turkish prosecutor is not a passive reviewer waiting for the police to complete the file. The prosecutor is the legal manager of the investigation phase. In practice, that means the police may carry out urgent field actions, but the investigation is formally prosecutor-led. That structure is one reason criminal investigations in Turkey often move through prosecutorial instructions very early, especially in cases involving search, seizure, questioning, custody, expert appointments, or requests for judicial authorization.
Immediate Investigative Measures at the Beginning
Some criminal investigations in Turkey begin with an immediate police intervention, especially in flagrante delicto or urgent conditions. Article 90 states that temporary apprehension may be made by anyone where a person is caught committing the offense, or where a person pursued because of a flagrant offense might escape or cannot immediately be identified. The same article also authorizes law-enforcement officers to apprehend in urgent situations requiring a detention order or arrest warrant where immediate access to the prosecutor or superiors is not possible.
Article 91 then regulates custody. If the person apprehended under Article 90 is not released by the prosecution office, custody may be ordered for completion of the investigation. The ordinary custody period cannot exceed twenty-four hours from the moment of apprehension, excluding the mandatory transportation period to the nearest judge or court, and the transportation period itself cannot exceed twelve hours. The article also makes custody dependent on investigative necessity and on concrete evidence showing suspicion that the person committed an offense.
These provisions matter because they show that some Turkish investigations begin with immediate coercive measures, but those measures are still tied to procedural control. The law does not say that every complaint automatically leads to custody. Nor does it allow open-ended detention at the beginning of the file. Instead, it builds a staged approach: apprehension in defined situations, custody only where necessary for the investigation and supported by concrete suspicion, and then prosecutorial and judicial control over what happens next.
The Investigation Phase Is About Both Evidence and Rights
A key feature of the Turkish model is that the opening of the investigation is also the opening of defense protections. Article 160 does not merely tell the prosecutor to investigate. It requires the prosecutor to collect and preserve evidence both for and against the suspect and to protect the suspect’s rights. That is especially important because Turkish criminal investigations can move fast. Statements may be taken early, digital evidence may be secured quickly, and liberty-restricting measures may be considered before the file is mature. The Code therefore insists that fairness is not postponed until trial. It begins at the investigation stage itself.
This is also why the prosecutor’s role is not simply accusatory in theory. At the start of a criminal investigation in Turkey, the prosecutor is supposed to test whether the allegation is real, whether the legal conditions for prosecution exist, whether exculpatory material needs to be preserved, and whether suspect rights are being respected during the first steps of the file. For defense lawyers, Article 160 is often the most important early procedural anchor because it allows them to argue not only against incomplete evidence, but also against one-sided investigation practices.
Documentation and Procedural Record
Turkish criminal investigations are also record-driven. Article 169 requires investigative acts such as suspect statements, questioning, witness and expert hearing, examinations, and inspections to be documented in minutes showing essential procedural information, including the identities of those present and the nature and timing of the act. This is important because the beginning of a criminal investigation in Turkey is not only about action; it is also about making the official record that later courts will evaluate.
That documentation function becomes decisive later. Whether the suspect was properly informed, whether a witness was heard lawfully, whether the police observed something directly, and whether the prosecutor took certain measures early may all turn on the investigation record. In practice, this means the file begins to build its evidentiary architecture from the first procedural steps, not only at indictment stage.
Diversion and Filtering Before Indictment
A Turkish criminal investigation does not always move straight from suspicion to indictment. The Code provides several filtering mechanisms that may intervene after the investigation has begun. One of them is deferment of public prosecution under Article 171. Except for mediation and prepayment cases and subject to further statutory exclusions, the prosecutor may decide to defer filing a public case for five years in offenses punishable by imprisonment with an upper limit of three years or less, even where sufficient suspicion exists, if the listed statutory conditions are met. Those conditions include the suspect’s lack of a prior intentional-crime prison conviction, a favorable assessment that the suspect will refrain from crime, a conclusion that deferment is more beneficial than prosecution for the suspect and society, and full remediation of the prosecutor-identified harm through restitution, restoration, or compensation. The law also excludes this mechanism for certain categories, including organized-crime matters, certain public-official offenses, military offenses, and offenses against sexual inviolability.
Another major filter is mediation. Article 253 states that mediation must be attempted for complaint-dependent offenses and for a number of specifically listed offenses even if they are not complaint-dependent. This means that the start of a criminal investigation in Turkey does not automatically imply a full adversarial prosecution path. In a significant category of files, the legal system first asks whether the case should be diverted into a consensual resolution track before a standard public prosecution proceeds.
When the Investigation Ends With an Indictment
If the collected evidence at the end of the investigation creates sufficient suspicion that the offense was committed, Article 170 requires the prosecutor to prepare an indictment. The same article states that the duty to open a public case belongs to the public prosecutor and that the indictment must include specific elements such as the suspect’s identity, the identities of the victim and complainant where applicable, the date of complaint, the imputed offense, the applicable legal provisions, the place and time of the offense, the evidence, and the detention information if the suspect is detained. Article 170 also requires the narrated events to be explained in connection with the existing evidence and requires the final section of the indictment to include not only points against the suspect but also points in the suspect’s favor.
This is a crucial stage in understanding how criminal investigations start in Turkey, because it clarifies the prosecutor’s ultimate threshold. The investigation begins at the much lower “offense impression” stage under Article 160, but it may turn into a public case only if the evidence rises to “sufficient suspicion” under Article 170. That distinction is fundamental. It explains why not every reported crime becomes a criminal case in court and why the investigation phase itself has independent legal significance.
When the Investigation Ends With Non-Prosecution
If the evidence collected at the end of the investigation does not create sufficient suspicion for a public case, or if prosecution is not legally possible, Article 172 requires the prosecutor to issue a decision of non-prosecution. The decision must be notified to the injured party and, if the suspect was previously questioned, to the suspect as well, and it must indicate the right to object, the time limit, and the competent authority. The same article also states that after a non-prosecution decision, the same act cannot later be turned into a public case unless new evidence creating sufficient suspicion is obtained and a criminal judgeship of peace gives a decision in that regard.
This is a key feature of Turkish criminal procedure. The investigation phase is not a mere prelude to indictment. It is an autonomous decision-making stage that may validly end with closure of the file. That is why the quality of the investigation matters so much. If the prosecutor fails to gather decisive material early, the file may end in non-prosecution. If the prosecutor later wants to reopen the matter, the law requires new evidence and judicial control.
Objection to Non-Prosecution
Article 173 gives the injured party a remedy. The injured party may object to the non-prosecution decision within two weeks from notification, by applying to the criminal judgeship of peace in the place where the heavy criminal court serving the prosecutor’s district is located. The objection petition must identify the events and evidence capable of requiring the opening of a public case. If the judgeship finds the objection justified, the prosecutor must prepare an indictment and submit it to the court.
This remedy is an important part of how criminal investigations function in Turkey because it prevents the prosecutor’s non-prosecution decision from becoming entirely unreviewable. At the same time, the structure of Article 173 shows that the objection is not just a protest. It must be tied to concrete events and evidence that could justify prosecution. That keeps the focus on the evidentiary logic of the investigation rather than turning the objection stage into a purely abstract grievance mechanism.
Court Control of the Indictment
Even when the prosecutor decides to indict, the court still acts as a gatekeeper. Article 174 states that within fifteen days after receiving the indictment and investigation file, the court may return the indictment to the prosecutor if it was prepared contrary to Article 170, if an existing item of evidence directly affecting proof was not collected, if mediation, prepayment, or the serial procedure should have been applied but was not, or if the offense required permission or request and the indictment was filed without such permission or request.
This is highly important in practice because it shows that a Turkish criminal investigation does not truly become a prosecution merely because the prosecutor drafts a charging document. The court performs a preliminary legality and completeness review. That means the quality of the investigation stage remains under judicial scrutiny even before the merits hearing begins. A weak or procedurally incomplete investigation can therefore delay or block the transition from investigation to prosecution.
Why the Starting Point Matters
The beginning of a criminal investigation in Turkey matters because it determines everything that follows: who controls the file, which evidence is gathered first, whether protective measures are used, whether diversion mechanisms apply, whether the suspect’s rights are protected from the outset, and whether the matter ends in non-prosecution or indictment. Turkish law deliberately makes the first threshold relatively accessible by using the “impression of an offense” formula in Article 160, but it also tries to control that accessibility by requiring prosecutorial leadership, documentation, suspect-rights protection, and later screening through sufficiency and judicial review.
In practical terms, this means the earliest stage of a Turkish criminal file is often the most legally important. Once the prosecutor or police learn of potentially criminal facts, the matter enters a structured legal framework. Complaints and notices may be filed through several routes. The prosecutor must begin investigating immediately. The judicial police act under prosecutorial authority. Coercive steps such as apprehension and custody are possible, but only under defined conditions. The file may then end with diversion, non-prosecution, or indictment depending on what the investigation actually produces.
Conclusion
So, how do criminal investigations start in Turkey? They start when legally relevant information about a possible offense reaches the authorities in a way recognized by law, most importantly the Chief Public Prosecutor’s Office, either directly or through police and other institutions. From that moment, the prosecutor must immediately investigate the truth, gather both incriminating and exculpatory evidence, protect the suspect’s rights, and decide whether the case should be diverted, closed, or brought to court by indictment. The process is prosecutor-led, evidence-driven, and structured by constitutional guarantees of fairness, legality, and remedy. For that reason, the beginning of a Turkish criminal investigation is not a mere administrative opening. It is the legal birth of the criminal case itself.
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