Normally, before delivering the verdict, the Judge will instruct the courtroom to refrain from any outbursts and maintain order. Herring may have interpreted that as not showing any signs, or Judge could have been tightening up because the high profile nature of the case.
All you need is a list of advertising keywords. Have the device treat those like wake words just like Alexa and then target ads to the device based on which words it heard most often.
This is but the most simple version, it’s easy to elaborate from there.