You thought the legal process was supposed to be open and transparent. Yet now the courtroom is closed. What's that about?
At the end of a trial, the judge must instruct the jury on what the law is in that particular case. The judge will instruct the court officer to close the courtroom for the hour or so while the judge is instructing the jury on the law.
The courtroom is closed so there are no interruptions. That's it. Plain and simple. During the entire trial, the courtroom is open to the public. People come and go.
When the judge is instructing the jury he does not want their attention diverted anywhere for any period of time.That is why the courtroom remains closed during the entire time the judge is instructing the jury on the law.