I"m not sure how the state could win at trial if they didn't have witness testimony to what happened. Guilt needs to be proven beyond a reasonable doubt. The criminal lawyer should know what evidence the state plans on relying on to obtain a conviction. Perhaps a written legal opinon from an immigration attorney as to the immigration consequences of a conviction to be given to the criminal lawyer to be used to negotiate with the prosecutor would be helpful. Often times when a prosecutor realizes they are going to destroy a family and don't have a good case they either dismiss the case or down file it.