"He did not have his lights on which I thought required him to obey posted traffic signs."

Aww, that's cute you still think cops actually obey any of the laws they don't want to.

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" In my defense I was using him as a pace car since I believed he was required to follow posted speed limits per MA CH 89 Section 7B. "

Terrible defense since that is like saying, "Your honor, I assumed I was going the speed limit because I was following a cop and it never occurred to me to look at my own speedometer."