I think this might help.

According to Iowa laws, a person may be eligible for expungement if -

1. A person who was acquitted or whose criminal charges are dismissed.
Persons acquitted or dismissed by reason of insanity and records of
adjudications of mental incompetence to stand trial in cases in which
physical or mental injury or an attempt to commit physical or mental
injury occurred are not eligible. Iowa Statutes § 692.17.

2.  A juvenile who has reached twenty-one years of age, unless the
juvenile was convicted of or pled guilty to a serious or aggravated
misdemeanor or felony between age eighteen and age twenty-one. Iowa
Statutes § 692.17.

3. Upon discharge from probation, a person whose judgment has been
deferred under section 907.3. Iowa Statutes § 907.9.

4. After two years from the of conviction of public intoxication, a
person who has had no other criminal convictions, other than simple
misdemeanor violations of chapter 321 during the two-year period. Iowa
Statutes § 123.46.