It’s difficult to know why your stepson behaves in a particular way without being able to interview him. Thus, my response will be general in nature.
It’s possible that his developmental delays are contributing to this problem. It’s also possible that he’s confused and does not fully understand the difference between truth and lies, or perhaps reality and non-reality. I’m also wondering if he’s ever sustained brain trauma or a head injury. Brain damage might also be contributing to his behavior.
I can’t help but wonder why he is taking a polygraph test in the first place? Was he forced to because of his criminal justice system involvement? Polygraphs are not fully reliable which is why they are not permitted in court. It has been theorized that they are measuring stress and not necessarily truth or lies.
Even if you understood the reason why he lies, it would likely not make it easier to deal with them. In all likelihood, his repeated involvement in the criminal justice system is distressing to the family. It would be advantageous to consult a family therapist who could assist your family in navigating these difficult issues. It’s best to utilize all available help and support.
If you would like to write back and ask more specific questions, I will then try to provide a more detailed answer. Hopefully, with the support of a counselor or other friends and professionals, you and your family can overcome these challenging issues. Thank you for your question.
Dr. Kristina Randle