Here is some expungement info re the state of Missouri:

In Missouri, under some circumstances, you may be able to have a criminal record expunged, which is the process of legally destroying, obliterating or striking out records or information in files, computers and other depositories relating to criminal charges.

You are eligible in Missouri for expungement if your arrest was based on false information and the following conditions exist:

There is no probable cause to believe you committed the offense
No charges will be pursued as a result of the arrest
You have no prior or subsequent misdemeanor or felony convictions
You did not receive a suspended imposition of sentence for the offense
No civil action is pending relating to the arrest or records sought to be expunged
If you qualify, you may file a verified petition for expungement in the civil division of the circuit court in the county of your arrest. The court then sets a hearing on the matter no sooner than 30 days from the filing of the petition. If the court finds that you are entitled to expungement of any record, it must enter an order directing expungement