Exegesis:

thelōn dikaiōsai heauton ‘wishing to justify himself,’ i.e. ‘to vindicate himself,’ or, ‘to justify his question,’ i.e. to show that Jesus’ apparently obvious answer was inadequate. The former is preferable. For dikaioō cf. on 7.29.

kai tis estin mou plēsion ‘and who is my neighbour?’ kai introduces a further question in a discussion.

Translation:

But he, desiring to … said, or, ‘but he (or, the lawyer/that man) desired/wished to … Therefore he said (or, asked).’

To justify himself, or, ‘to vindicate himself,’ “to put himself in the right” (Good News Translation), ‘to show that his question had been right.’ Sranan Tongo has, ‘to pull himself out of the story,’ used when a person tries to withdraw from a discussion that becomes unpleasant; an English-Chinese equivalent would be, ‘to save his face.’

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.