Can you just imagine the questions that would be posed to her at a press conference? "Why did Kyron's bio mother immediately feel that you had hurt her son"..."did you have an affair with the LSer"...."Why do KH and DY not believe you are doing the right thing" (whatever that is)..."Do you always sext men other than your husband"... puleeeze, gimme a break.
Any decent defense lawyer in the country will tell you that it is always a bad idea to speak out, and actually, they will also tell you that it's a worse idea to talk to the cops without representation. Police interrogators are highly trained to get people to say the wrong thing. Read up on the Innocence Project and learn how many people have been wrongly convicted, many of them by their own words, twisted by detectives who were cocksure they had the right guy.
Naturally in a case with a missing child, a stepmother couldn't reasonably not talk to the police or agree to the polygraph. The big however,imho, is the question that caused her to "fail". I will bet dollars to donuts that that question had to do with her sexual escapade with the LSer and nothing at all to do with Kyron's disappearance.
I think it is suspicious the way she was kept out of the public's eye, when the family finally deigned to speak. There was the missed golden opportunity to hear her side of the story. And the fact that Terri was omitted from the PCs with KH and DY because "they" wanted to hear from the bio parents was a slap in her face. She was treated terribly considering that she was Kyron's daily caregiver. The little boy was in her company and under her care a whole lot more than one or two weekends a month, for years. This omission in itself cast TH as a person under suspicion, in the public's eye. It made her an outsider of the "family". I often wonder who made that decision.
She is 100% right in remaining silent. If she is guilty of Kyron's disappearance and/or murder, let them prove it.
So far, I have seen assumptions of her guilt based on nothing but suspicion, innuendo and "feelings". I need a lot more than that to condemn the woman.