I believe that minor traffic violations are considered non-criminal matters in most states.
Techinically they are handled like criminal case and traffic laws are part of
criminal penal code. There are three type of crime - felony, misdemeanor,
and infraction. Traffic violations are in infraction. Technically all three types
are crimes but in practice people do not call infraction crimes
In Mass, traffic violations are pursued like civil trial.
You will be found liable not guilty. Some rules like hearsay rule do not
apply. It is very ironic but actually these state make traffic violation civil case in
order to find an easy way to punish traffic violation because burden of proof is much lower
in a civil trail than a crminal trial. Since there is almost no jail term for
traffic violation and it is all about collecting money, Masssachussetts and
a few other states figure why not just de-criminalize them and make them
civil matter/
Hearsay may not apply so a police do not need to testify against you.
A letter from the police who issue teh ticket is good enough.
Massachussettis also unique in that speed limit is not meant to be
absolute on many state roads. Driving above speed limit is legally allowed as
long as one can reasonable assume it is safe. That is why many people
in Mass dare to openly drive 20 miles above speed limit even in presence of
a police car because it is not really speeding as long as it is safe.