The Investigation Phase in Turkish Criminal Procedure

The investigation phase in Turkish criminal procedure is the first formal stage of the criminal process and one of the most decisive. Under the Code of Criminal Procedure, the “investigation” begins when the competent authorities learn of a suspicion of crime and continues until the indictment is accepted; once the indictment is accepted, the prosecution phase begins. The Code also distinguishes the suspect in the investigation phase from the accused in the prosecution phase, which shows that Turkish law treats the investigation as a legally distinct stage with its own actors, powers, and rights. This is not a merely preparatory administrative period. It is already part of criminal procedure in the strict sense.

That structure matters because Turkish criminal procedure does not wait until trial to activate fairness guarantees. The Constitution protects the right to a fair trial, the presumption of innocence, the privilege against self-incrimination, and the rule that findings obtained through illegal methods cannot be treated as evidence. It also guarantees access to effective remedies and requires the State to indicate the legal remedies, competent authorities, and deadlines available in its proceedings. As a result, the investigation phase in Turkey is not simply about collecting accusations. It is a legally regulated stage in which the State must investigate within constitutional limits from the very beginning. (Anayasa Mahkemesi)

How the Investigation Phase Begins

The basic starting rule appears in Article 160 of the Code. A public prosecutor must begin investigating the truth immediately when the prosecutor learns, through a complaint or in any other way, of a situation giving the impression that a crime has been committed. The prosecutor’s duty at that point is to determine whether there is ground to open a public prosecution. This means the investigation phase in Turkish criminal procedure begins at a relatively early threshold: not when guilt is proven, not when evidence is complete, and not only when a victim files a formal complaint, but when the prosecutor becomes aware of facts that create a criminal-offense impression.

Article 158 explains the formal routes by which criminal information reaches the authorities. A criminal notice or complaint may be filed with the Chief Public Prosecutor’s Office or with law-enforcement authorities. If it is submitted to a governor’s office, district governor’s office, or a court, it must be forwarded to the relevant Chief Public Prosecutor’s Office. For offenses committed abroad but prosecutable in Türkiye, notices and complaints may also be made to Turkish embassies or consulates. The same article states that a notice or complaint may be made in writing or orally so that it is recorded in minutes. Turkish law therefore makes entry into the investigation system procedurally accessible and does not require citizens to master institutional routing in advance.

At the same time, Turkish law also contains a filtering mechanism at the very threshold. Article 158 provides that where it is clear, without any investigation, that the reported act does not constitute a crime, or where the notice or complaint is abstract and general in nature, a decision of no need to investigate may be issued. In that situation, the reported person cannot even be given the status of suspect, and the complainant or informant may object under the procedure linked to Article 173. This is an important point for understanding the investigation phase: not every allegation automatically matures into a full criminal investigation. The Code draws a line between a legally meaningful offense impression and purely abstract or obviously non-criminal assertions.

The Prosecutor’s Role in the Investigation Phase

The public prosecutor is the central legal actor in the Turkish investigation phase. Article 160 does not merely tell the prosecutor to investigate; it gives the prosecutor a balanced mission. In order to discover the material truth and secure a fair trial, the prosecutor must collect and preserve evidence both against and in favor of the suspect through the judicial police, and must also protect the suspect’s rights. This is one of the most important structural principles in Turkish criminal procedure. The prosecutor is not legally designed as a purely one-sided accusatory officer at the investigation stage. The Code expressly imposes duties of balance, legality, and rights-protection.

Article 161 then gives the prosecutor broad authority to fulfill that role. The prosecutor may conduct any research directly or through the judicial police and may request all kinds of information from public officials in order to reach the result envisaged by Article 160. Judicial police officers are required to report apprehended persons, seized incidents, and protective measures to the prosecutor immediately and to carry out the prosecutor’s judicial orders without delay. Prosecutorial orders may be written, and in urgent situations may first be given orally, but oral orders must be put into writing as soon as possible. In practical terms, this means the investigation phase in Turkish criminal procedure is prosecutor-led even when police officers perform many of the visible steps on the ground.

This prosecutorial centrality also explains why the legal quality of the early file matters so much. If the prosecutor follows Article 160 properly, the investigation will not consist merely of accumulating incriminating material. It will also include preservation of favorable evidence, screening of legal defects, and attention to whether coercive measures are actually justified. For defense lawyers, Article 160 is often the most important early provision because it provides a textual basis for arguing that the investigation must be complete, balanced, and fair before the State can move toward indictment.

The Role of the Judicial Police

The judicial police occupy a distinct place within the Turkish investigation phase. Article 164 defines judicial police by reference to the security units authorized to carry out investigative acts, and Article 164 further states that investigation acts are carried out primarily by the judicial police under the orders and instructions of the public prosecutor. Where necessary, other police units may also be required to perform judicial-police functions, and when they do so, the Code applies to them in that judicial capacity as well. This means that Turkish law sharply distinguishes ordinary policing from the judicial-police function performed inside criminal procedure.

The importance of that distinction becomes even clearer when the Code describes supervision and recording. Article 166 authorizes chief public prosecutors to prepare annual evaluation reports on local judicial-police supervisors, while Article 168 allows the judicial police already working at the crime scene to prevent interference with the measures they have lawfully taken until the operation is completed. These rules show that the judicial police are not acting in a legally unstructured space. Their investigative role is embedded in prosecutorial direction and statutory procedure. In the Turkish investigation phase, the police are not the independent masters of the case file; they are functionally subordinated to prosecutorial legality.

Confidentiality of the Investigation

Article 157 states that investigation-stage procedural acts are confidential, unless the law provides otherwise, but it also adds an important qualification: confidentiality must not harm the rights of the defense. This is one of the defining tensions of the investigation phase in Turkish criminal procedure. The law wants to preserve the integrity of the investigation, protect evidence, and avoid premature disclosure, yet it also recognizes that secrecy cannot be used to destroy defense rights. Turkish law therefore does not recognize absolute investigative secrecy. Instead, it recognizes a qualified form of confidentiality bounded by the requirements of defense.

That balance becomes especially important in practice because the investigation phase often includes urgent evidentiary measures, early statements, and possible requests for custody or detention. If secrecy is interpreted too broadly, the defense may be prevented from understanding the accusation in time. If it is interpreted too weakly, the investigation may be compromised. Article 157 resolves that tension by anchoring secrecy to the preservation of defense rights. In other words, the investigation phase is confidential in Turkish law, but not at the price of turning the suspect into a powerless outsider to the process.

Judicial Participation During the Investigation

Although the prosecutor leads the investigation, some acts require judicial participation. Article 162 states that when the prosecutor considers it necessary to carry out an investigative act that only a judge may perform, the prosecutor must apply to the criminal judgeship of peace in the place where the act is to be carried out; the judge then decides whether the requested act is lawful and, if so, ensures it is performed. Article 163 adds that in flagrante delicto situations or in urgent cases where the prosecutor cannot be reached, or where the scope of the event exceeds the prosecutor’s practical capacity, the criminal judgeship of peace may itself carry out all investigative acts. This demonstrates that the Turkish investigation phase is prosecutor-led but judicially supervised where the law reserves power to the judge.

This judicial involvement matters for legality and legitimacy. Searches, seizures, detention requests, and other coercive or rights-sensitive acts often depend on judicial authorization or review elsewhere in the Code. Even when the investigation is still pre-indictment, Turkish law does not allow the executive side of the criminal process to expand indefinitely without judicial control. The investigation phase is therefore not only an evidentiary stage. It is also a stage in which the allocation of powers between prosecutor, police, and judge becomes crucial to the legality of the file.

Suspect Rights During the Investigation Phase

A defining feature of the investigation phase in Turkish criminal procedure is that defense rights apply early. Article 147 requires that when a suspect’s statement is taken, the suspect must be informed of the accusation, of the right to choose counsel and receive legal assistance, of the possibility that counsel may be present during questioning, and of the right not to make statements about the accusation. The suspect must also be reminded that he or she may request the collection of concrete evidence that may remove suspicion and must be given the opportunity to put forward matters in his or her favor. This is an unusually strong formulation because it recognizes not only passive rights such as silence, but also an active right to shape the evidentiary record during the investigation phase itself.

Articles 149 and 150 reinforce that framework. The suspect may benefit from one or more defense counsel at every stage of the investigation and prosecution, and during the investigation up to three lawyers may be present during statement-taking. The lawyer’s right to meet the suspect, be present during questioning, and provide legal assistance cannot be prevented or restricted. If the suspect cannot select counsel and requests one, counsel must be appointed; in some cases, such as for children, persons unable to defend themselves adequately, or investigations concerning offenses carrying a higher statutory minimum threshold, counsel is appointed even without a request. These rules show that the Turkish investigation phase is not conceived as a lawyer-free zone later corrected at trial.

Article 153 gives defense counsel the right to inspect the investigation file and obtain copies of requested documents without charge, subject to some statutory limits in sensitive matters, while Article 154 states that the suspect or accused may meet counsel at any time, without a power of attorney, in an environment where others cannot hear the conversation and that correspondence with counsel cannot be monitored. Article 148 adds that the suspect’s statement must rest on free will, prohibits coercive methods such as torture, ill-treatment, deception, threats, exhaustion, and similar interventions, and provides that statements obtained by prohibited methods cannot be used as evidence. It also states that a police statement taken without counsel cannot be used as the basis of a judgment unless later confirmed before a judge or court. Together, these provisions make clear that the investigation phase is already a full rights-bearing stage.

Recording and Evidentiary Structure

Article 169 regulates how investigative acts are documented. The taking of a suspect’s statement or interrogation, the hearing of witnesses and experts, and inspections or examinations must be recorded in minutes. Those minutes are signed by the judicial police officer, public prosecutor, or criminal judge, and by the clerk present. If counsel or a representative is present, the lawyer’s name and signature must also appear in the record. The minutes must state the place, date, start and end time, and the names of the persons participating in or connected with the act; relevant sections are read or provided to the interested persons for review, and refusal to sign is also recorded. In Turkish criminal procedure, the investigation phase is therefore not merely oral or informal. It is documentary from the outset.

That recording structure has major practical consequences. Much of what later happens at trial depends on whether the investigation record was made lawfully and accurately. Questions such as whether the suspect was informed of rights, whether counsel was present, whether a witness was heard correctly, or whether an investigative step occurred within the lawful time and scope often turn on the minutes. For that reason, the documentation rules of Article 169 are not minor administrative requirements. They are part of the evidentiary architecture of the entire criminal case.

How the Investigation Phase Ends

The investigation phase does not continue indefinitely. Under Article 170, if the evidence collected at the end of the investigation creates sufficient suspicion that the offense was committed, the public prosecutor prepares an indictment. The indictment must include, among other things, the suspect’s identity, the victim or injured party where relevant, the offense charged, the applicable legal provisions, the place and time of the alleged offense, the evidence, and detention information if the suspect is in custody or detention. Article 170 further requires that the facts constituting the alleged offense be explained in relation to the existing evidence and that the concluding part of the indictment include not only points against the suspect but also points in the suspect’s favor. This is a critical bridge between investigation and prosecution in Turkish law.

If that standard is not met, Article 172 requires the prosecutor to issue a decision of non-prosecution where sufficient suspicion has not been established or where prosecution is not legally possible. The decision must be notified to the injured party and also to the suspect if the suspect’s statement or judicial interrogation has previously been taken, and it must indicate the available objection route. Article 173 then allows the injured party to object within two weeks to the criminal judgeship of peace in the place where the heavy criminal court sits, and the objection petition must identify the facts and evidence capable of requiring a public prosecution. These provisions show that the Turkish investigation phase is not simply a path to indictment; it is an autonomous decision-making stage that may lawfully end with closure of the file.

Even when the prosecutor chooses indictment, the file is still screened before the prosecution phase formally begins. Article 174 allows the court to return the indictment within fifteen days if it was prepared contrary to Article 170, if existing evidence directly affecting proof was not collected, if prepayment, mediation, or serial procedure should have been applied but was not, or if a legally required permission or request was missing. Article 175 then states that the public case is opened and the prosecution phase begins only upon acceptance of the indictment. This is why the investigation phase in Turkish criminal procedure formally lasts until indictment acceptance, not merely until indictment drafting.

Alternative Endings Within the Investigation Phase

Turkish law also recognizes alternatives between full prosecution and outright closure. Under Article 171, apart from certain excluded offense categories and without prejudice to mediation and prepayment rules, the prosecutor may defer the filing of 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 statutory conditions are met. These include the suspect’s lack of a prior intentional-crime prison conviction, a favorable assessment that the suspect will refrain from further offending, a conclusion that deferment is more beneficial than immediate prosecution, and remediation of the identified harm. This shows that the investigation phase may produce differentiated outcomes rather than a strict binary of indictment or non-prosecution.

Mediation is another important example. Article 253 provides that for complaint-dependent offenses and for certain specifically listed offenses, an attempt at mediation must be made between the suspect and the victim or injured party. This means that the investigation phase in Turkish criminal procedure also functions as a procedural sorting stage. It is the phase in which the system decides not only whether there is enough evidence, but also whether the dispute belongs in ordinary public prosecution at all or instead fits one of the legally recognized alternative mechanisms.

Why the Investigation Phase Matters So Much

The investigation phase matters because it determines the legal shape of the criminal file before trial ever begins. It is the stage in which suspicion is tested, evidence is gathered or lost, defense rights are activated, coercive measures may be sought, and the prosecutor decides whether the case should be closed, diverted, deferred, or charged. The Code’s structure makes clear that this phase is not legally secondary to the trial. On the contrary, Articles 160 through 175 show that the Turkish criminal process depends on a properly conducted investigation if the later prosecution phase is to be lawful and fair.

For that reason, a sound understanding of Turkish criminal procedure must treat the investigation phase as a complete procedural stage in its own right. It begins when the authorities learn of a criminal-offense impression, proceeds under prosecutorial leadership and judicial supervision where required, remains confidential without destroying defense rights, includes robust suspect protections, and ends only when the prosecutor’s decision has either closed the file, diverted it, or produced an indictment accepted by the court. In Turkish law, the investigation phase is where the criminal case is first built, first tested, and often first won or lost.