I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
Getting a legal declaration that your marriage is void unfortunately won't necessarily result in the charges being dismissed - then you're just filing something in court that acknowledges your marriage as invalid due to the prior marriage. That's essentially an admission of guilt and could actually be used against your husband in court, since that's a public record. Your husband has to be able to establish that he reasonably believed that his first marriage had been dissolved, that he reasonably believes his first wife died before he married you, or that he had some reason for believing the original marriage was void. In that case, it would be a question of fact whether (a) he held the belief and (b) whether his belief was reasonable. Any time there is a question of fact, the jury has to determine what happened, which means he may have to go to trial.
Bigamy is a felony of the third degree, which means that your husband has a constitutional right to have a lawyer help him with the case. He doesn't have to deal with it on his own. If you cannot afford to hire an attorney, the judge will appoint one for him at the initial appearance. His lawyer can review all of the relevant facts, talk to your husband about what he thought happened to his first marriage, and either help prepare defense for trial or try to negotiate a plea bargain that will allow your husband to reduce the impact of this charge.
In order for the two of you to be lawfully married, he will have to file a Petition for Divorce from his first wife, and then you can get married after it's granted. If he is unable to locate her, he can request that she be served by publishing notice of the divorce action in the legal notices section of a small local newspaper. This is fairly common, and any local family law attorney can help with that.
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