The usher takes oaths from witnesses and jury members.
The oath or affirmation is a promise. Witnesses promise to tell the truth and members of the jury promise to give the defendant a fair trial. This is what they say.
1. Jury members:
I swear that I will faithfully try the defendant and give a true verdict according to the evidence
I swear that the evidence I am about to give is the truth, the whole truth and nothing but the truth.
The Usher also carries written questions from the jury to the judge.