I will state this, once again, as best I can: an expert witness has absolutely nothing to do with the defense building process, merely reinforcement and in certain circircumstances, the dismantling of said defense. What is so difficult to grasp here?
Does an expert have any access to the building process of a case in terms of defense? No. They do not receive any intrigal information in regards to the case. The Lawyer asks "Your opinion, Dr?" but is not required to give names, locations, dates, times or other pieces intergalactic in the judicial process. The expert witness gives their opinion based upon the info that they do receive.
A lay witness can, in certain instances i.e. coroner. But an expert witness has no basis to plan the actual defense, like I've stated before. Opinions are opinions and facts are facts. There isn't anything there to debate. You might be thinking of affirmative witnesses that can be utilized by the defense itself, but again that's the lawyer choosing to do so. The expert witness does not decide on the jury panel, to further cement the point.
They have nothing to do with how a legal team decides to implement their plan. Such instances can then become conflicts of interest and even perjury when an expert witness is cajoled one way or another.
Calling me out and telling me that an expert witness maintains constant contact with the defense attorney on all legal defense matters is ludicrous. The expert witness cannot tell the defense lawyer how to do their job, that's up to the legal defense team. That's silly to think that way. There wouldn't even be a need for defense attorneys in that case then if all they had to do was hire expert witnesses.
Expert witnesses are a tool that the defense (and the prosecution) uses to fortify their position, nothing more and nothing less.
Does that make any sense? I don't know how else to explain it.