(151) break down / give away / link up with … / less long in the tooth
I can believe in Rogers killing his wife because he was scared of her breaking down and giving him away, or because he’d taken a dislike to her, or he wanted to link up with some nice little bit rather less long in the tooth.

「break down」はここでは「ノイローゼになる」。「give away」はここでは「裏切る」。「link up with …」は「・・・とつながる」。「less long in the tooth」は「もっと若い」。

(152) deal out
But I can’t see him as the lunatic Mr. Owen dealing out crazy justice and starting on his own wife for a crime they both committed.”

「deal out」は「を与える、加える」。

(153) have it your own way
Lombard said:
“Well, have it your own way.

「have it your own way」は「お好きなように」の意。

(154) on the score of
“My point is that there can be no exceptions allowed on the score of character, position, or probability.

「on the score of」は「・・・の理由で(on the ground of)」。

(155) to put it simply
“To put it simply, is there among us one or more persons who could not possibly have administered either cyanide to Anthony Marston, or an overdose of sleeping draught to Mrs. Rogers, and who had no opportunity of striking the blow that killed General Macarthur?”

「to put it simply」は「簡単に言えば」。