The prolongation of criminal proceedings has long been a problem that has confronted the judicial system. Delays in proceedings exist to a greater or lesser extent in many judicial systems, so that the absence of delays in proceedings in a judicial system is considered strange. The phenomenon of delay in proceedings exists in both civil and criminal cases, but unfortunately, delay in proceedings, especially in criminal matters, has reached worrying dimensions in our country. One of the important issues related to the field of delay in proceedings is the issue of reasonable time in criminal proceedings. In other words, before talking about the causes of delay in proceedings, it should be basically determined how long the duration and time of handling a case is a normal and natural period and amount and when should we talk about delay in proceedings. In determining a reasonable time for criminal proceedings, the best source is the European Convention on Human Rights and the Court. This convention discusses the reasonable and fair time limit for a criminal trial, and the European Court of Human Rights has explained the reasonable time limit for criminal trials in its various opinions. Therefore, in order to determine what is a reasonable and normal time limit for handling criminal cases, referring to this convention and the opinions of the European Court can be very helpful. The Court uses criteria to determine a reasonable time limit; something that can also be applied in criminal trials in our country.