I'm taking Lover's court analogy seriously, for the moment--assuming it is an American court. An expert witness must present credentials, answer questions, and be accepted as a authority by the judge before being allowed to offer an opinion. He then may only be asked questions within his expertise.
The expert may be retained by either defense, prosecution, or the court.
Using that standard, I don't think that Jason Colavito has anything to offer in this case to anyone: prosecution, defense, or the court.
I could imagine Jon Ellison to be accepted as an art expert to discuss brush strokes: he has credentials and proven expertise. But, I'd expect it to be very narrow--and the "other side" might want to seek out their own expert.