Luke records an inscription over Jesus declaring, 'This Is the King of the Jews.' Such an inscription is more than a theological title placed into the story; it belongs naturally to the public and punitive character of Roman execution.
The charge identifies Jesus' alleged kingship at the very place where Roman power appears to have defeated him.
Roman punishments could publicize the offense of a condemned person, reinforcing the deterrent purpose of execution. The Gospel traditions describe a written notice associated with Jesus' cross, while John gives additional detail about its wording and languages.
In Roman Judea, unauthorized kingship was politically sensitive because sovereignty ultimately rested with the emperor and rulers acceptable to Rome.
The historical practice explains why the title appears at the cross. Spectators are being told why this man is being executed.
The Gospel simultaneously creates a profound irony: Rome displays 'King of the Jews' as an accusation and humiliation, while the evangelists present Jesus' kingship as true in a sense neither the executioners nor the mockers understand.