Being separated from your father and then discovering the possibility that he was unjustly brought to trial for the murder of your mother can be extremely traumatic in later years. I have no doubt that she is being well cared for now. However, there are long term ramifications of the murder trials. Not to mention that she is not developing a relationship with her father, which can also be harmful to her upbringing and later life.
When it comes to children, however, especially children in their tender years - the court considers only the best interest of the child. That includes the child's stability, the child's safety, the caregivers' ability and willingness to allow the child to maintain relationships with other family members/extended family - especially when a parent is deceased.
And there's a weighing of the potential harm and the gravity of that harm.
Jason Young has been indicted for first degree murder of Cassidy's mother. In addition he was actively alienating Cassidy from any of her mothers side of the family.
Although Jason Young is innocent under the law until proven guilty, the family court is not so interested in whether the State can prove beyond a reasonable doubt that Jason murdered CY's mother. They consider whether there's enough evidence to justify restricting JY's access to Cassidy, and the family court is going to err on the side of caution to protect the child.
Not developing a closer relationship with her father is an acceptable outcome for the child when weighed against the possibility of her being physically harmed or killed by her father.
If Jason Young were given primary custody, and he didn't allow MY's family to maintain a relationship with her - then there's much more turmoil if he's convicted, and CY is either placed in foster care or moved to relatives who have become strangers. Worse, if Jason is a murderer and suffers from certain personality disorders, Cassidy's life could be at risk if Jason decides to end it with murder/suicide, rather than face life in prison and give up his daughter to his accusers.
See Joshua Powell case for example
http://deseretnews.com/article/7053...-family-Susan-Powells-sister-says.html?pg=all