Mark 15:27

‘And with him they crucify two brigands, one on his right hand and one on his left.'

All the Gospels, including John, stress that Jesus was in the middle between two brigands. It identified Him as one of them. Mark sees this as symbolic, probably having in mind ‘He was numbered with the transgressors' (Isaiah 53:12), as a copyist would appositely later point out (Mark 15:28 is an insertion). There is an irony in that these brigands had the places that James and John had so eagerly sought (Mark 10:37). Those who would share His glory, must share His sufferings.

The brigands may well have been two insurrectionists who had committed murder along with Barabbas (Mark 15:7). In this action Jesus was identified with them, as just another Jewish troublemaker. But His superscription declared differently. That may be why He was put in the middle as being the most important.