You can file a petition to seal anytime after your deferred adjudication has been successfully completed, although the length of time that as elapsed since completion of your deferred is one factor that the court will consider in determining whether to seal.
For certain offenses there are notice requirements prior to filing, and you must demonstrate that your privacy interest in sealing the records outweighs the public interest in having your criminal records remain unsealed. I would definitely recommend hiring a lawyer to handle this for you to make sure all of the proper arguments are made on your behalf.
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