The twin inside me.

This programme follows the case of Lydia Fairchild who has one of the world's rarest syndromes which almost led to the loss of her chidlren. After the birth of her third child, Lydia applied for welfare benefits but the DNA tests showed that she couldn't be their mother. What followed was a lengthy court battle which was only resolved after the story of Karen Keegan came to light. Keegan developed kidney failure and needed a transplant which led to medics testing the DNA of her children. Like Fairchild DNA tests showed that she couldn't be the mother of her 3 sons. Doctors became intrigued by her case - could there be a medical reason for this difference in DNA? While Fairchild was being investigated by the US government for benefit fraud Keegan's research team were discovering that she might have two separate sets of DNA in one body - a rare condition called chimerism. Fairchild was found to have chimerism and allowed to keep her children. But the US court was left with a dilemma - if DNA is not reliable, it can no longer be used as court evidence.