这里的 before 是在“某人面前”“当……的面”的意思,直译就是:本案是在陪审团面前审理的。通顺版:本案由陪审团审理完毕。
详见《牛津高阶英汉双解词典》before:
in the presence of sb who is listening, watching, etc. 当面
He was brought before the judge.
他被带上法庭。
She said it before witnesses.
她当着证人的面讲出这事。
They had the advantage of playing before their home crowd.
他们有在主场观众面前比赛的优势。