Possible consequences for alien from mexico to use another person identity under TX law

The person should immediately review his facts and options with an attorney.

Committing identity theft is not only a federal crime but likely also a state crime. There may be a statute of limitations that limits the government's ability to prosecute.

Besides the criminal aspects, since this person was not born a US citizen, whatever immigration benefits he received while misrepresenting a material fact (lying about his identity) may be revoked. Generally, this is no statute of limitations on the government to revoke immigration benefits obtained by lying.

The person likely should not be discussing the details of his case with anyone but his attorneys. He likely should not be making any declaration without the advice of his attorneys.