Are people who work in the criminal justice system allowed to be on juries?

I know that when a jury is being picked, people are rejected if they have some kind of connection to the case. Once, my mother was even rejected because I had a foot injury and the case for which she was going to be on the jury dealt with a leg injury of some kind.

So, with this in mind, wouldn’t an employee of the criminal justice system know too much about the inner workings of a trial and criminal justice system in general to serve on a jury?