Re: Would you trust a USA court ...
That happens quite a lot if you challenge traffic tickets. The cop who issues the ticket has to show, if they don't you get the ticket dismissed. The downside is that its potentially a lot of work to get to this stage and there's always a chance the cop will show. Most people just pay the ticket.
This is a whole different deal. The Federal court system is very different and a lot more dangerous than a state or municipal court. Right now I'd suggest that all extradition requests from the UK are routinely denied unless two things happen -- first of all, the US shows it has a case and second Mrs Sacoolas is returned to answer charges of causing death by dangerous driving (the UK has been told to 'pound sand' by US authorities).