The demise of Socrates may be taken as unjust from a Christian perspective in that one of the charges against him was that of impiety ("not believing in the gods of the state"). Here one could argue that Socrates was neglecting man's law in order to fulfill a "higher law." However, the issue then becomes if he was even pious in the correct form, maybe believing in the true God? That is, neglecting man's law in order to abide by God's law. I do not think this was the case with Socrates.
From the view of the Athenians, Socrates was justly punished. He was corrupting the youth of Athens and impious. If it truly was an unjust charge, trial, and punishment against him, in my opinion it would not be wrong to attempt an escape. One could argue the preservation of life or the "unjust law is no law at all" for justification.
What do you think?