If you have already established he is in Estelle Unit, or at least an inmate by that name, you might want to try contacting the prison by phone. I’m sure there must be an established protocol for this situation when people are looking for long lost family or loved ones that may be incarcerated. I would start with a phone call or at least a letter to the administration. Be prepared to show them ID on your end.

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"Thats it then, they will go on double, secret, probation..."