I don't think he can have his record expunged unless he gets a pardon. Pardon's aren't easy to get either.
http://www.uslegalforms.com/lawdigest/expungement-criminal-records-law.php/TX/TX-EXP.htm
Who is eligible to get records expunged?
Under Tex. Code Crim. Proc. Art. 55.01, a person is eligible for expunction if acquitted or convicted and pardoned or meet the following conditions:
1) an indictment or information charging the person with commission of a felony has not been presented or has been dismissed or quashed; and the statutory limitations period has expired; or the indictment or information was dismissed or quashed for lack of probable cause; and
2) the person has been released and the charge, if any, has not resulted in a final conviction and is no longer pending and there was no court ordered community supervision; and the person has not been convicted of a felony in the five years preceding the date of the arrest.
A person can get expungement for a criminal conviction reversed on appeal. Persons whose identifying information was falsely used without consent by an arrested person may seek expungement of such information. Expungement isn’t available if charges arose out of a criminal episode, as defined by Section 3.01, Penal Code, and the person was convicted of or remains subject to prosecution for at least one other offense occurring during the criminal episode.
As permitted by Tex. Code Crim. Proc. Art. 45.051, a juvenile who has completed a deferred sentence may seek expungement under § 55.01.
Under Tex. Code Crim. Proc. Art. 45.053. involving the dismissal of a misdemeanor charge on commitment of a chemically dependent person, records relating to a complaint dismissed under this article may be expunged under Article 55.01.
If the court finds that the person was not convicted of any other offense described by Section 8.07(a)(4) or (5), Penal Code, while the person was a child, the court shall order the conviction, together with all complaints, verdicts, sentences, and prosecutorial and law enforcement records, and any other documents relating to the offense, expunged when turn 17. Tex. Code Crim. Proc. Art. 45.0216.
Also, under Texas Alcohol and Beverage Code § 106.12, a first-offender of underage drinking violation may have records expunged. Must not have any other violations under the Alcohol and Beverage Code while a minor to be eligible and submit a sworn statement to that effect to the court.