Who is Responsible for Unpaid Bill

[cactus]

My question involves collection proceedings in the State of: Utah.
medical services for a child were performed in 2008. The mother was the responsible parent, responsible for paying, parents did not live at same address, she had sole custody, and bills were apparently sent to her and/or her insurance at the time. Even so, most bills were paid by the father at the time of service.
One bill was not paid. It was sent to the mother, and denied when her insurance lapsed. Father never knew about it.
In 2011 a Utah debt collection service contacted Father wanting him to pay. He'd never seen the bill. If the bill was sent in mother's name, to mother and her address, to her denied insurance - is father's credit rating able to be immediately damaged? And what is his responsiblity?
Since 2008 the father has got sole custody and child now lives with him. He pays all medical anyway. But is it true, as collection agency says, that he is respponsible for this bill even if it isn't in his name and was never sent to him, and the mother was listed as responsible parent?

[jk]

a parent is liable for their child's bills. Each parent would be jointly and severally liable to the provider. That means the provider could seek payment from either parent or both. If one or the other is liable due to a court order concerning custody and support, that means the parents need to deal with each other for who ultimately is liable but that does not involve the provider. That is between just the parents.

So, dad should pay the bill and if the court order is that mom pays, then he can go to court to seek and order for her to repay him. They have no business trying to get a provider in the middle of their arguments.