Check to see MA law on how police can check your speed. If he did not use a radar gun, but used his vision to estimate, this is a method some states allow, however you could more easily argue that one (you could request a copy of the officers last cert for this estimation process to see how long ago it was, photograph the area he was parked and see how his visibility was to your vehicle, etc)

Ha, I have a Subaru and had winter tires in the past but didn't get a new set last winter. Needless to say I was on my all-seasons which are near the end of their life and wasn't sure if it was my tires or the roads being crazy I see today, but I was sliding laterally after coming to a stop and am currently looking into buying another set of winter tires after that haha. Glad to hear that someone with blizzaks was having trouble out there as well and it wasn't just my tires