If you are a prosecutor, the defendant is well-known and probably not going to run off to Venezuela and you have up to three years to file a felony charge and up to two years to file a misdemeanor, you can subpoena witnesses to Grand Jury to get sworn testimony as to what actually happened and you want to actually win any case that is filed, not just arrest the defendant, 

18 days is hardly 'ignoring' a case.  And when you are talking about Felony or Misdemeanor, that is sometimes the difference between a "Physical Injury:" or a "Serious Physical Injury" as those terms  has been defined in the law and interpreted by the courts.

ORS 161.015 (7) Physical injury means impairment of physical condition or substantial pain.
(8) Serious physical injury means physical injury which creates a substantial risk of death or which causes serious and protracted disfigurement, protracted impairment of health or protracted loss or impairment of the function of any bodily organ.