If you and your husband cannot afford an attorney, the Court will appoint one for him. If he is in jail, this probably has already been done. Although public defenders carry heavy caseloads, they usually are especially effective with cases of mistaken identity. They have a self interest in clearing the case as soon as possible and they generally have a lot of credibility with the judges and prosecutors. Since the state provides public defenders, lawyers generally do not volunteer their time as pro bono (free) attorneys in this type of case. Good luck.
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If someone stole his identity and went through the criminal justice system you should consult a civil attorney about the possibility of suing the sherrif's office that arrested him. If he's in jail and cannot afford an attorney, the Court will appoint the PD for him to try and resolve the case. Fingerprints are usually taken after a plea, so that would be a good place to start.