"We are of the view that to interpret New Jersey Rule of Evidence 615 to authorize the routine sequestration of expert witnesses in a matter such as this is contrary to the terms of New Jersey Rule of Evidence 703, which provides that an expert may base his opinion upon 'facts or data . . . perceived by or made known to the expert at or before the hearing.' By its use of the preposition 'at,' the rule clearly envisions an expert observing trial proceedings and then commenting upon what he has heard." State of New Jersey v. Popovich, February 19, 2009