If you were only charged with sexual assault and not convicted, your record is eligible to be expunged.
However, if you were convicted and your conviction was in Arkansas the answer to your question depends on whether you have a felony conviction or a misdemeanor conviction.
If you were convicted of a felony sexual assault, your record cannot be expunged.┬á However, you can attempt to have your conviction pardoned in 2012.┬á (You have to wait 8 years after your conviction to apply for a pardon).
If you were convicted of a misdemeanor sexual assault, if you were required to register as a sex offender you cannot get an expungement.┬á However, if you have a misdemeanor conviction and were not required to register as a sex offender, you are eligible to have your record expunged.
Hope that helps.