When I did jury service, we were warned about 'the six week trial' (with only a few days notice) and to get our excuses/reasons in order if we couldn't commit to it. It would have been similar for this trial.
When they did the jury pre-selection, they started with 24 people, which I was one of. People were selected and had to give a reason to the judge if they couldn't/didn't want to do it.
So things that were acceptable were prebooked holidays or planned surgery. One man said he was the main carer for his elderly parents. Someone else said they were self employed and it would significantly impact their business to not work for that long. I was picked and managed to argue that, while my employer had been able to rearrange my work for the two weeks, six weeks was too much as I had commitments with external stakeholders that would be detrimental to our and their interests for me to miss and I had a letter confirming this. The judge reluctantly accepted this. But obviously they needed 12 people who could commit.
Anyone who's got responsibilities for young DC and would struggle with childcare would be able to defer until they were older if needed.
But for those who did serve, it could have been that their employers would get in temps, or give extra shifts/work to co-workers, depending on what type of work they do. But obviously this isn't possible for all, which might be how you'd be excused.
I'd expect in a 10 month trial, there would be some significant breaks, possibly even scheduled, as people working on the trial would still be entitled to statutory annual leave, so you might know that you have a window to go on holiday.