Exegesis:

hostis ēn … blētheis en tē phulakē ‘who had been thrown into prison.’ The relative clause is attached to the direct speech of v. 18, but is not part of it. It is added in order to give information about Barabbas after his name has been mentioned, and is best treated as an independent clause in parentheses. The periphrastic construction ēn … blētheis is equivalent to a pluperfect. en is here equivalent to eis.

dia stasin tina genomenēn en tē polei kai phonon ‘on account of a rising that had happened in the city and of murder,’ implying that Barabbas had something to do with the riot and was responsible for a murder committed during the riot.

Translation:

A man who had been …, or as a new sentence, ‘(This) Barabbas, (or, This man) had been…,’ ‘Barabbas was a man who had been….’ In some cases it is preferable to start the sentence with the description of the situation, e.g. ‘There had been an insurrection in the city and a murder, and as a result (or, and for this reason) this man had been…’ (cf. The Four Gospels – a New Translation, Batak Toba).

Thrown into prison, or, ‘imprisoned,’ cf. on “shut up … in prison” in 3.20. If an active construction is required, one can best use an indefinite agent (cf. e.g. Sranan Tongo, ‘they’), or take Pilate, the Romans, or the Roman authorities as agent(s) or initiators.

For an insurrection started in the city, or in a verbal clause, ‘because people had begun to riot in the city,’ ‘because people in the city had fought the ruler’ (cf. Tae’ 1933).

Murder, or, ‘someone had been killed’ (Tae’ 1933), ‘he had committed a murder, or, had killed a person.’

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.