@OverByYer
No he can’t be compelled to attend but the case can be heard in his absence. He now needs to decide which will be the best option.
Apparently he could simply not give evidence, which would avoid any chance of a repeat car-crash (bearing in mind it would be under oath*)
However a quick skim suggests that this would not be subject to the 5th amendment (which only covers criminal cases) so the court would be allowed to draw conclusions from such a decision.
Maybe someone more conversant with US law would know ?
*If he were to give evidence under oath, and it turned out to be false, would he be subject to a criminal charge for which he could be extradited ?
I think his woes have only started.