After assuming office as the Caliph, the first case that Uthman was to try was the case of Ubaidullah. Apart from Abdur Rahman b Abu Bakr no other person supported the theory of any conspiracy. Adequate evidence was thus not forthcoming to support the theory of the involvement of Jafina and Hurmuzan in the alleged conspiracy. Again, even if it was established that these persons had entered into a conspiracy, there was no justification for the killing of the wife and daughter of Firoz. Even if there were strong prima facie grounds for holding that the assassination was the result of a conspiracy, the State alone could have tried the accused and condemned them only when they had offered their defense, and the case was established against them. Ubaidullah had no right or justification to take the law in his own hand and murder four persons without affording them an opportunity for defense. That was the Arab practice of the days of ignorance which was in violation of the injunctions of Islam.

The case was tried by Uthman with the help of a jury. The jury included Ali, Amr b Al A'as and some prominent Companions. Ali was of the opinion that the dictates of justice demanded that Ubaidullah should be executed for taking the law in his hand, and murdering four citizens without cause. Ali was emphatically of the view that in Islam, law was no respecter of persons, and Ubaidullah could not be saved from the penalty of law merely on the ground that he was the son of the late Caliph.

Amr b Al A'as and other companions were of the view that they lost Umar only yesterday, and it could not be that today his son should be killed. They said that they owed to the memory of Umar that his son should be protected.

Uthman pondered over the matter. He said that as the murdered person had left no heir, he was their heir, and in this capacity it was open to him to accept blood money for the murdered persons. His verdict was that Ubaidullah should pay a thousand diners as blood money, for each murdered person.

Ubaidullah was not in a position to pay the blood money. Uthman paid the blood money out of his own pocket and credited it into the Baitul Mal