Can an officer in AZ issue a citation for speed failure to avoid collision if he wasn’t witness to the collision?

I was recently in a motor vehicle accident, I was going home from work at roughly 7-8pm when another driver made a left turn into a liquor store without making sure the roadway was clear and I slammed into their passenger side tailgate. I told the officer I was going the speed limit (40mph) but he cited me for going an estimate of 45 mph. I plan on fighting the ticket as the officer can’t prove I was going over the speed limit (which I wasn’t) and also failed to write a narrative of the incident. Also because I was issued the citation the other parties insurance is denying liability even though the report clearly states they failed to yield the right of way.