Q: Did the mother have any legal responsibility .......

A: Asked and answered: https://answers.justia.com/question/2017/08/06/my-husband-has-been-alienated-from-his-s-302365

As far as I know there is no requirement that the mother reports when the son stops living with her and frankly it wouldn't be workable. The custodial parent is entitled to receive support even when the child is away from home such as to go to visit the other parent or to go to a school program. The support can continue while the child is a run-away. The idea is that the custodial parent is maintaining the household with nearly the same expenses as if the child where at home and there is an expectation that the child will come home again. You can't really gauge what was going on day by day from the son's story. The mother may have been trying tough love with the hopes that the son would come home. He may have been using drugs and she wanted to help him but didn't want to fund his drug habit. The general rule with child support is that it continues as an enforceable judgment until the one of the parties files to amend it. There are no do-overs.

Again, the father did not make efforts to enforce his parental rights during this period. He was the adult and he could have found out what was going on if he had been pro-active with enforcing his rights to have contact with his son. The sad part is that you want to help get money for the absentee father because you feel that it shouldn't have been paid to the mother while the son was living on the street - and you don't account for the father not taking steps to be in the son's life at that critical period where the father should have been intervening to help his son or recognizing that his son needed help.

You also made the argument in one of your posts that the support should have been going to the son. But you don't consider that if the son was getting into trouble experimenting with drugs and alcohol as most teenagers do, that giving him money would have fueled the problem. Also you don't explain why the son didn't reach out to his father when he was going through this turmoil. (In my experience the more a custodial parent bad mouths the other parent the less the children believe it.)

In theory the father is guilty of child neglect. Yes I know the he was alienated due to the mother's actions but the father had the courts that would have helped him have contact with his son. His neglect to fight to be in contact with his son. While not a criminal act, it is a form of child neglect. I would assume he knew what problems were likely to happen between his son and the mother as he had some idea as to her personality and he didn't stay in a position where he could protect his son.