It is the branch of public law examining the concepts of crime and punishment. It is divided into two: public and private criminal law (referred to as public criminal law and private criminal law).

The public criminal law covers such general issues as the definition of the concept of crime with tangible and intangible elements, general principles prevailing in the criminal law, definition of the concept of punishment, reasons eliminating the crime and reasons alleviating and eliminating the crime.

The private criminal law covers such general issues as the acts constituting crime as per the applicable legislation, their scope and limits, their distinguishing aspects and the penalties for these crimes.

It is a legal principle, requiring that one cannot be punished for doing something that is not prohibited by law. This basic principle is stipulated in the first paragraph of Article 2 of the Turkish Criminal Code No: 5237: "No punishment shall be imposed on or security measures shall not be applied against any person who does something not expressly declared as a crime under law." This requires that the definition of crime is clearly and explicitly regulated by law. Crime may not be defined with unclear and vague expressions (nulla poena sine lege certa).

Another requirement of the legality is that no punishment may be imposed without a previous penal law. In other words, no one may be punished for an act that was not a crime then but then it was criminalized under a regulation (nulla poena sine lege praevia).

One of the most basic requirement of the legality is the prohibition against analogy. Legally speaking, the analogy refers to the case where the legal gaps are filled with the most similar cases. In the criminal law, the analogy may not be applied as stipulated under third paragraph of Article 2 of the Turkish Criminal Code No: 5237: "No analogy shall be made in the application of criminal and penal provisions of the law" (nulla poena sine lege stricta).

In the criminal law, crime is a deliberate and intentional commitment of a punishable act. That’s, to be punished, the perpetrator must deliberately and intentionally commit the crime. Based on this understanding, the principle that only the perpetrator must be punished has been adopted. This principle is also included in the first paragraph of Article 20 of the Turkish Criminal Code No. 5237: "Criminal responsibility is personal; no one can be held responsible for the actions of anyone else."

Certain elements must exist in order for an act to constitute a criminal offense. The main elements that constitute the crime are the legal element, the tangible element, the illegality element and the intangible element.

The legal element is that the criminal offense must be fully in conformity with the definition of the crime in the criminal law. This element is called typicalness. For an act to be considered as theft, “a movable belonging to someone must be taken without the permission of its owner in an effort to ensure benefits for oneself or others”. In the absence of one of these elements defined under the law, for example, if the permission of the owner is obtained, there shall be no legal element of the crime of theft.

For the offense to take place, the perpetrator must commit an act. The perpetrator must be engaged in an act to change the outer world. For example, reflex movements or movements of patients with epilepsy when they lose consciousness are not criminal elements.

We can talk about the illegality element in case where the act is in nonconformance with the legal order. In principle, an act that is in nonconformance with the legal order is illegal. However, the criminal law introduces a number of exceptions to illegality and establishes that certain acts completing legal elements shall be in accordance with the law, including:

The last element constituting the crime is the deliberate and intentional offense by someone responsible for his/her actions in contravention of the applicable legal order. At the same time, this element is a reflection of one of the universal principles of criminal law, which says there is no perfect crime and punishment. Even if an action carries all the elements mentioned above, it may not require punishment of the perpetrator in the absence of the intangible element and deliberate intention.