To sit on the jury

Hi,
I heard "to sit on the jury" somewhere.
Does anyone know what the means?

Well, the literal meaning is to be part of the panel of the public chosen to decide guilt or innocence of an accused person in the more serious cases (in the UK and Ireland anyway). Other countries have slightly different rules, but most will be similar to that. In the UK and Ireland there are usually 12 jurors.

More broadly, it is to take part in any more or less official decision-making procedure. So, for example, a beauty contest might have a jury picking the winner.

DFG

More simply, it means to be a member of a jury.

*slaps own head* I never thought of the obvious answer!