英語版FF9日誌83 : I shall petition for a life sentence on his behalf.

スタイナーは飛行船でガーネット姫を城へ連れ帰れると確信し、独り言を言っています。

Steiner:

At last! Queen Brahne is sure to be pleased.

However... the princess would have been left behind without the thief's aid.

I shall petition for a life sentence on his behalf. Yes, that would be the honorable thing! But that was because the crew wouldn't listen! I must run a background check on them. Ah, yes. It is my duty as a knight!

 I shall petition for a life sentence on his behalf. 

 petition「嘆願する」

life sentence 「終身刑」

on his behalfは「彼の代わりに、代理で」という意味です。