Succession and death
After 572, Justin was reported to have fits of insanity. John of Ephesus, whose Monophysite sect suffered persecutions under Justin, offered a vivid description of Justin's madness, in which he behaved like a wild animal, was wheeled about on a mobile throne and required organ music to be played day and night.
Despite moments of clarity, Justin was no longer able to govern. Eastern Roman sources report that Tiberius, the commander of the Excubitors, directed the government from this point, alongside Sophia. In 574, about a year after his incapacitation, Justin elevated Tiberius as Caesar at Sophia's suggestion and adopted him as his son. On 7 December, according to Theophylact Simocatta, Justin remained sufficiently clear-minded to make an eloquent speech as he passed the crown:
You behold the ensigns of supreme power. You are about to receive them, not from my hand, but from the hand of God. Honor them, and from them you will derive honor. Respect the empress your mother: you are now her son; before, you were her servant. Delight not in blood; abstain from revenge; avoid those actions by which I have incurred the public hatred; and consult the experience, rather than the example, of your predecessor. As a man, I have sinned; as a sinner, even in this life, I have been severely punished: but these servants (and he pointed to his ministers), who have abused my confidence, and inflamed my passions, will appear with me before the tribunal of Christ. I have been dazzled by the splendor of the diadem: be thou wise and modest; remember what you have been, remember what you are. You see around us your slaves, and your children: with the authority, assume the tenderness, of a parent. Love your people like yourself; cultivate the affections, maintain the discipline, of the army; protect the fortunes of the rich, relieve the necessities of the poor.
However, as time passed Justin's mental health grew worse and he became suicidal, asking for people to kill him with a sword, "for death, he would say, is better for me than a life of such anguish and agony". Four years after he made Tiberius Caesar, Justin begun to suffer from bladder stones. His physicians performed surgery on him, but the process was a failure and the cuts sustained from the surgery were fatal. As his death became inevitable, on 26 September 578, in a moment of lucidity, he elevated Tiberius as Augustus. According to John of Ephesus, he said to Tiberius:
I, my son, am dying: go now, take the royal crown, but be on thy guard, that thou be not guilty of sin, and provoke God to anger: and consult for the good of the kingdom of the Romans.
Justin died only nine days later, on 4 October 578.