(a) Upon reviewing the report, the court shall determine whether the defendant has been in the custody of the Department of Mental Health and Developmental Disabilities (now the Department of Human Services) for a period of time equal to the length of time that the defendant would have been required to serve, less good time, before becoming eligible for parole or mandatory supervised release had he been convicted of the most serious offense charged and had he received the maximum sentence therefor. If the court so finds, it shall dismiss the charges against the defendant, with leave to reinstate. If the defendant has not been committed pursuant to the Mental Health and Developmental Disabilities Code, the court shall order him discharged or shall order a hearing to be conducted forthwith pursuant to the provisions of the Code. If the defendant was committed pursuant to the Code, he shall continue to be treated pursuant to his commitment order and shall be considered a civilly committed patient for all purposes including discharge.
     (b) If the court finds that a defendant has been in the custody of the Department of Mental Health and Developmental Disabilities (now the Department of Human Services) for a period less than that specified in paragraph (a) of this Section, the court shall conduct a hearing pursuant to Section 104-20 forthwith to redetermine the issue of the defendant’s fitness to stand trial or to plead. If the defendant is fit, the matter shall be set for trial. If the court finds that the defendant is unfit, it shall proceed pursuant to Section 104-20 or 104-23, provided that a defendant who is still unfit and who has been in the custody of the Department of Mental Health and Developmental Disabilities (now the Department of Human Services) for a period of more than one year from the date of the finding of unfitness shall be immediately subject to the provisions of Section 104-23.