The Trial Before the Sanhedrin
Church of Sant'Apollinare Nuovo, Ravenna
This is one of the 13 narrative mosaics along the right wall of the nave. Standing beside Jesus is an accuser in the same clothing, hair, and beard as the associate of Caiaphas in the Way of the Cross panel and (possibly) the Pharisee in the panel on The Parable of the Pharisee and the Publican. His dalmatic and chasuble most likely signify some sort of religious status (see this image of a contemporary bishop).
Caiaphas the High Priest sits on the left end of the bench. Like his colleagues, he wears red and white boots and a mantle with an ornate pectoral clasp. The mantle and clasp are also worn by Aaron, the original High Priest, in this painting from the 3rd century and this ivory from the 10th, and by Melchizedek in two other local mosaics, one from the 7th century and one from the 6th. In the latter, Melchizedek also has the red-and-white boots worn here by the Sanhedrin.
The Sanhedrin's tunics, with the paired shoulder-to-hem stripes, perhaps suggest their dependence on the Romans. Elsewhere in these mosaics, only soldiers wear tunics; the stripes resemble those in images of Roman senators (example).
Caiaphas has the same garb and hair in subsequent panels on Judas' regret, The Trial Before Pilate, and the Way of the Cross.
The scene is based on Matthew 26:57-68, Mark 14:53-65, Luke 23:66-71, and John 18:12-24.
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View the entire right wall
See also a view of the entire left wall with commentary on the iconography of Jesus and the apostles in these mosaics.
More of the Trial Before the Sanhedrin
Photographed at the church by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.
Sant'Apollinare in Classe has this mosaic of Ursicinus, Bishop of Ravenna (533-536), wearing shoes and a white pallium over a folded chasuble over a white dalmatic. This is the typical garb in which Ravenna's bishops were pictured. It has some similarities to the shoes, chasuble, and dalmatic of the accuser in the Sanhedrin scene, although the latter has no pallium and his dalmatic has no stripes.
Here is a third-century fresco from the Hypogeum of the Aurelii in Rome, showing the purple stripes on the togas of senators:
Source: website of Dr. Dorothy King