Criminal background reports are only supposed to show arrests and convictions, but sometimes the record of SIS and probation does show up. The reason for this is that data brokers search casenet and find the records, save those records, and then later sell them to potential employers who purchase your criminal background report.
Employers seem to be more concerned with honesty than if you had a criminal case in the past. For that reason, I think it is best to disclose the criminal case before the potential employer sees it on a background check.