MOO: It sounds like a person who has exceptionally strong self-belief but few social skills. I doubt it's a lawyer. A high street practitioner specialising in conveyancing, remortgaging, filling in tax forms and representing alleged shoplifters would be likely to show much more deference in such illustrious company, and if they were higher up the scale I think the collegiality would kick in. If the aetiology is law-related and Dunning Kruger-flavoured it might possibly be somebody who dropped out of a law course way back when, or who is long retired. But I'd go for someone who has social work, medical, or state schoolteaching connections, perhaps not as a current occupation but at one remove. We should count ourselves lucky insofar as there haven't been any reports of them shouting "Objection!" at any point. Hopefully they haven't done more than display questionitis and petition for the court's timetabling to be rearranged. I can easily imagine a fellow juror telling them that they've said an awful lot, and that if they can manage to keep quiet for a whole day the other jurors may possibly be able to get their disagreements sorted. I say this from the POV of feeling that a verdict is preferable to no verdict.
PS I opposed lifting the pre-2004 restriction on letting lawyers serve on juries. Most lawyers I knew at the time opposed it too. It was kinda sweet to hear them say that as lawyers they'd never know from personal experience what went on in jury rooms. They thought that was a good thing.