All that we know of his life comes from the Vita which Flavius Josephus apparently wrote in response to the assertions made by Justus in his History of the Jewish War, published around 93/94 or shortly after 100.
Thus in the ninth century, Bishop Photios of Constantinople was still able to access a copy of the Chronicle of the Jewish Kings' written by Justus.
[5][6][7] He attacks Justus at length, even though he had not even mentioned him — nor his father Pistos — in The Jewish War written twenty years earlier.
[8] He criticizes him for multiplying the errors[9] — but without citing any explicitly — and for “not having had access, unlike him, to the field notes of Vespasian and Titus".
[13] However, despite Josephus' efforts to blame Justus for the uprising in Galilee, several facts he mentions in his Vita contradict this accusation.
After the Great Jewish Revolt (66-70), he was imperial secretary at the court of Agrippa,[26][27] king of Batanea and the eastern part of Galilee[1] (Vita 356).
Josephus compares Justus and all the historians who lie “out of hatred or partiality” to “forgers who fabricate false contracts (V § 337)".
[30] It was only after Agrippa's death that Justus published his History of the Jewish War, which triggered the writing of the Vita' of Flavius Josephus.
[26] If that had been the case, it is unlikely that Josephus, who devotes a great deal of space to the attacks on Justus in his Vita, would not have mentioned them.
[34] Justus also held that Josephus and his army of Galileans were responsible for anti-Roman actions against his city of Tiberias[38] (Vita 340 and 350).
[38] When he arrived in Galilee the first thing that Flavius Josephus recounts in his Vita is the destruction of the palace that King Agrippa possessed in Tiberias, followed by the murder of all the Greek inhabitants of the city.
According to him, when he had not entered the city, he asked the authorities of Tiberias to destroy Herod's palace which contained paintings violating the aniconism advocated by certain tendencies of Judaism.
[14] Josephus claims that he simply took this booty from the hands of the criminals and gave it to Julius Capella, leader of the tendency of those who wanted "to remain faithful to the Roman people and to their king"[39] in order to preserve the interests of Agrippa[14] (V 68-69).
[40] One of the major differences between the Jewish War and the Vita is the frequent mention of Justus of Tiberias in the latter text, whereas Flavius Josephus does not say a word about it, in what he had written twenty years earlier.
[26] If that had been the case, it is unlikely that Josephus, who devotes a great deal of space to the attacks on Justus in his Vita, would not have mentioned them.
[42] If this attitude of Titus became an imperial policy continued after his death, it perhaps explains the rapid disappearance of Justus of Tiberias' book on the History of Jewish Warfare.
It is likely that several later authors used this material in their own works, such as Sextus Julius Africanus, Eusebius, Diogenes Laërtius;[48] and the Byzantine historian George Syncellus.