If someone is being accused of a charge(rape) what depths would a detective to see if the allegations were fal?

My son was wrongly accused and convicted of rape of my nieces two oldest kids.When police filed the report it stated that the little girl had a secret to tell her mom and that her little brother told her(sister)that it happened to him too. My sons Atty. told him not to worry about the little boy it was here say and the charges for the little boy would be dropped. So my son and I both put that out of our minds. By the end of the proceedings my son was found guilty of all counts including the little boys. The Judge said if he found any discrepancies in the testimony then he would have to find my son not guilty. During lunch my sons attorney said it was looking good Judge heard some discrepancies then before returning to court room attorney came back to my son and offered him 15 yrs. and suggested that he take. Well he didn't because he didn't do it. I am 500 % sure and I am not saying this because he is my son..for one he is no saint..not even close..he gave me hello growing up and has a record but no complaints of being sexually aggressive..so now all of a sudden he is a convicted rapest. He had a sexually transmitted disease when they said it first happened..then the time frame of the offense changed. I had documentation from the hospital. Attorney didn't turn it over to prosecutor..??What do I do..he is no saint but life for something he did not do..Polygraph attorney sent us to Richland ohio 10 minutes before procedure he called and told us it was Richfield. I asked him to reschedule for a M-W-F because T-T I had to take husband to dialysis..same days every week..attorney has it scheduled for T-T ..than said son refused polygraph..I need help..PLEASE!!!!