I got called in for jury duty this past summer. Sounds like the process is almost identical in Canada.
Then we found out it was a murder trial and you can see all the air sucked out of the room since everyone knew this could take a long time.
I run my own business and can't be away, so I was going to make that argument. Fortunately they formed the jury before I got called up. So I was dismissed and that was the end of it.
To be honest, I'm game for sitting on a jury later in life. Since I did my civic duty and showed up when called on, apparently I won't get called on again for 3 years. I may be out of my business by then so I won't have a legitimate reason not to and am curious to do it.