‘And those who had taken Jesus led him away to the house of Caiaphas the high priest, where the scribes and the elders were gathered together.'
After a private examination under the shrewd Annas (John 18:19-24), probably in his private rooms in Caiaphas' palace (he was Caiaphas' father-in-law), a pre-examination which failed to produce what they were hoping for, (a grounds for convicting Jesus), Jesus was led away to Caiaphas where a larger group of Chief Priests, Scribes and Elders had by this time gathered. There were thus representatives present from all three sections of the Sanhedrin, although probably hand-picked. As it was still Passover night they would have been somewhat hastily gathered, and no doubt, as anyone who knows anything about politics will know, selected with some discrimination as to who was invited (politicians never change. Only their names change).