In mitigation, ...

冇錯，我以前都查過舊的字典，真是冇這個字。但mitigating factors 及mitigants or mitigators 我都在文章見過。有「補償」的意思。如先形容或批評某一件事怎樣不好，但後來文講番D好嘢，這就是其migating factors或 mitigant了。
如銀行借出無抵押的公司放款，在審核時，會考慮有沒有其他「可補償性」的理由，如該公司的聲譽，debtors的quality等。這就是mitigants 了。The corporate loan is basically unsecured, However,in mitigation, the debtors' quality is quite good. 

2009-08-06 11:02:46 補充：
不是exactly 「in addition」的意思，但有些補償性的意思，請参考以下網頁:

http://hk.knowledge.yahoo.com/question/question?qid=7007040503364

另約前年，「合和」在灣仔打算起一mega tower，居民大力反對，話會引起交通擠塞，出入不便, ........etc. Finally, the developer , in mitigation, promised to build a 24-hour walkway accesssible to .........

2009-08-11 22:25:40 補充：
查較新字典如The New Shorter Oxford English Dictionary，mitigate解作lessen the trouble caused by或to make less severe.

至於In mitigation, 該字典有例句如下:

He was found guilty. I refused to make any statement in mitigation.

2009-08-11 22:30:44 補充：
另一本New Oxford Dictionary of English 2003提及:

-to make ( something bad) less severe, serious or painful.

In mitigation so as to make something, especially a crime, appear less serious and thus be punished more leniently.例句為 In mitigation , she said her client had been deeply depressed.