It is highly unusual for anyone to go to jail for failure to pay child support as it serves no purpose whatsoever (I speak for Los Angeles County only but suspect it is probably the same in San Francisco). If the payor (dad) of child support is put in jail then he cannot work, and therefore, can never pay off the child support arrears. That doesn't help anyone--not the child, not the mom, and not him.
Are you sure you have the facts of your friend's case correct? It may be that the local child support agency intercepted his driving privileges, i.e., suspended his driver's license. If that has happened, then it is a relatively easy fix with an attorney's help.
Once arrears have been accumulated, moving to another state is not a solution. The payee (mom) can register the child support order in the other state, and his wages can be garnished, his bank account levied, his tax return intercepted, etc.
The best option is for your friend to consult with an experienced family law attorney to solve the problem, not avoid it. Child support arrears accumulate 10% annual interest, so ignoring the problem just makes it worse. It is possible to propose a settlement of the arrears, but he will probably have to hire a lawyer to help him do so. I hope this information helps. Good luck to you and your friend.
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No, the friend does not have the ability to clear him of the warrant. If he is ever stopped by a police officer for any traffic and/or other legal violation, he could be arrested.