The police officer, highway patrol trooper, or the sheriff's deputy; merely allege a violation occurred.
A citation is issued, which also serves as a summons (in lieu of a physical arrest), and the driver's promise to appear is acknowledged by his or her signature.
In some cases, the prosecutor will summarily dismiss a citation before or upon the appearance date.
In other cases, such as your son's, the prosecutor will amend the charge (upward or downward) prior to the appearance date.
In most cases, its always wise to investigate traffic school or deferred adjudication.
Fewer than 5% of traffic court defendants receive anything other than a guilty verdict.