Assalaam-alikum, my question is about "Judge as witness in Islam"example; Judge who was seen his own eye attacks and murder, full scenes. if Judge sees all those is he able to fish the case by himself as a witness or testimony?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The jurists differed in opinion about whether a judge may pass a judgment based on his own knowledge. Some of them said it is prohibited and some said it is permissible. For instance Ibn Rushd said in Bidaayat Al-Mujtahid:

"They (the scholars) differed in opinion about whether a judge can rule in favor of someone according to his knowledge without evidence or testimony, or whether he is not to judge except with the evidence that is presented to him and the testimony (of the disputing parties)? Maalik and most of the scholars of his School said: the judge is not to judge except with either evidence or testimony. This is also the view of Ahmad and Shurayh. Ash-Shaafi’i, Al-Koofi, Abu Thawr and a group of scholars said: the judge may pass a judgment based on his knowledge. Both parties based their views on the pronouncements of Companions and Successors (Taabi‘een) … On the other hand, Abu Haneefah and his companions particularized the matters in which a judge may make a decision based on his knowledge, saying that a judge is not to make a judgment based on his knowledge in matters of Hudood (crimes with prescribed punishments), i.e. in Zina, theft, wine consumption and slander, but he can judge in other matters. Abu Haneefah and his companions also particularized the type of knowledge which a judge can base a decision on, saying he may judge with knowledge he acquired after taking the position of judge but not with knowledge he acquired before taking the position of judge." [Abridged]

The scholars who disagreed with this cited as evidence a Hadeeth from ‘Aa’ishah saying that the Prophet, sallallaahu ‘alayhi wa sallam, sent Abu Jahm ibn Huthayfah to collect Zakah. A man was obstinate in paying the Zakah, so Abu Jahm struck him, causing him injury. His people came to the Prophet, sallallaahu ‘alayhi wa sallam, seeking retribution, so the Prophet, sallallaahu ‘alayhi wa sallam, made a few offers before they finally agreed. Then, the Prophet, sallallaahu ‘alayhi wa sallam, said that he would address the people about the agreement, and they agreed to that. Addressing the people, the Prophet, sallallaahu ‘alayhi wa sallam, said: "The Laythis came to me seeking retribution and I made them an offer to which they agreed. Do you agree?" They said no (denying that they had agreed). Now, the Muhajiroon wanted to fight them, but the Prophet, sallallaahu ‘alayhi wa sallam, told them to refrain from doing so, so they refrained. Then, the Prophet, sallallaahu ‘alayhi wa sallam, called on them in and made a higher offer.

The point here is that the Prophet, sallallaahu ‘alayhi wa sallam, knew that they agreed to a certain amount but when they denied it, he did not judge against them with the knowledge that he had about their agreement, but instead made a higher offer.

Concerning the reason for it being prohibited, the scholars also said that it is so that corrupt judges do not find a way to claim knowledge about someone who they would like to judge in their favor. They also said that if this door were left open, every judge would find a way to kill his enemy and call him a criminal, and to separate him from those who likes, and therefore it is obligatory to prevent the permissibility of judgments based on knowledge in these later times because of there being many people who have assumed the office of judge and who cannot be trusted in that.

Based on this view, a judge should not pass a judgment in a crime which he has seen but should instead be a witness rather than a judge.

The scholars who say that it is permissible for a judge to make a judgment based on his knowledge provide as evidence a Hadeeth from ‘Aa'ishah saying that Hind Umm Mu‘aawiyah said to the Prophet, sallallaahu ‘alayhi wa sallam: "Abu Sufyaan (her husband) is a stingy man. Is there any sin on me for taking some of his money secretly? He (the Prophet) said: Take enough for you and your children in a reaonable manner."

The point here is that the Prophet, sallallaahu ‘alayhi wa sallam, made a judgment based on his knowledge without listening to her opponent.

Allaah Knows best.