interest rates on child support outstanding balance

Factual Questions
1

An employee of my brother-in-law owes back child support, and the government has decided to get him in gear by tacking on a 12% PER MONTH interest rate until he is payed up. (I am not advocating for either side here, just curious).

Question: Who determines these rates? Is there any limit to how high these rates can go?

2

The courts determine the rate and it is based on state usury limitations for the type of debt.

3

Do they actually charge that? I’m familiar with extortionate rates of penalties used to make people wake up a negotiate. Could that be the case? And who gets it - the spouse or the agency?