Nissan Repair: Wrong ECM, honda prelude, emissions test

Question
I'd like to hear your opinion on the following situation:
My mechanic put in the wrong used ECM in my 1992 Honda Civic.  I finally took the Honda to a Honda leadership and they found out that he put in a used ECM for a Honda Prelude.  Of course, my car malfunctioned, and I failed my emissions test with the ECM he put in. I got the proper computer part number from Honda, and bought the part off of EBAY and the car worked as it should after the ECM was installed.  My question:  is the mechanic negligent in putting in the wrong used ECM.

Answer
Howard,

If he knew that it would not work then he would be wrong.  But, many fit multiple years and models and if that was the case he was just doing what the book said.  I personally like to stick with the same year and type...  But, that is because I have had this problem before...