Since the earliest times in Islamic jurisprudence, witness has always maintained its importance as a means of proof. In addition to some verses around the subject in the Qur'an, it was shaped by some practices of the Prophet Muhammad (Peace be upon him). As in various positions of Islamic law, the existence of a religious and conscientious side of witnesses attracts attention. According to this, it is seen that the fulfillment of the witness by people has an original characteristic with the voluntary control system. Besides the determining methods of the presence of certain possessions that witnesses must cary and the handling of this issue in the sources points out an existence of historical developments. According to the acceptance of the majority of Islamic lawyers, witnesses should be found to have good morals. This process is also referred to as amendment or attestation. After the witness declaration, the judge himself is expected to make an inquiry regarding the determination of the title of justice, to produce prevailing presumption about the witness and make his decision only after that. The practices in this direction have progressed from the earliest times, in the practice of Second Chaliph Omar and later in the fatwas of Imam Abû Yûsuf and Imam Muhammad from Hanafî school of thought, and it is observed that there is a wealth of information scattered in the sources. It is seen that the investigation and attestation about the credibility of the witnesses is defended more detailed in the sources of Hanafî, Shâfiî, Hanbalî school of thoughts and Mâlikî sect and has gained a distinct importance in time. In general, the Hanafi's have observed the view of two imams/Abû Yûsuf and Imam Muhammad, and accept their mentioned view and operate it in the judiciary, when giving fatwa in the process of investigating the state of the witnesses. Finally this is also known by everybody that it is made law in Majallah. With the adoption of the Civil Code, Turkish law was satisfied with the oath of witnesses and the procedure of witness investigation was dismissed. Here by pre-acceptance idea that in front of the law everyone has the title of being witnesses, the way of attestation was suspended. As a reason, certain difficulties and complaints are cited as justifications. Wheras, the fact that the requirement of the investigation of witnesses today and the fact that positive results can be obtained can simply be predicted. It is therefore seen possible in courts to avoid making decisions based on false witness statements unknowingly and unintentionally and thus being cautious at the beginning of the work. There is a procedure of witness investigation which is tried out in Islamic law and is connected to certain principles. With the help of technical communication tools such as computer, internet and judicial networks, the tasks of courts and judges can be made more efficient in terms of reasoning. In Islam, religion, faith, worship, law, morality and human factor perform an integrated task. The role of this issue is great in attestation, in the realization of general justice, in the correctness of court decisions, in the reduction of judicial mistakes, in the establishment of public order, and in the well-being of good morals among individuals in society. A statistical decline occur willingly or unwillingly in the crime, punishment and misdemeanor rates in the society as a result of religious, moral and conscientious autocontrol in individual sense, and, as a result of fear of an investigation by the judge one day, in the public sense.