The one thing that I personally took from both RB's and DdH's communication style is that they use obfuscation tactics to render all forms of verbal interaction redundant.
In RB's case he slips and slides around using numerous deflection and avoidance techniques, he literally contradicts things that he only a few minutes ago or in a previous hearing agreed or answered. His word means nothing. DdH was more of 'dunno...', 'can't remember...'. Her word also means nothing IMO.
To me this speaks of deliberate knowing guilt and is somewhat understandable from a criminal mindset. Why would anyone logically or rationally confirm, deny, or admit, to any single fact on the subject of anything if helping someone gather those facts could move towards a bad situation for yourself.
They may as well have just openly stated we aren't going to contribute towards our own downfall, thanks for asking. Can a person be morally, ethically, or legally *compelled* to answer questions? I would say this is a situation they've both given a lot of thought to and found a way to beat the system somewhat by only outputting literal verbal garbage.
JMO MOO