A perhaps bad analogy: what if this were DNA evidence? Does the defense and prosecution both need to do their own analysis of a sample? Or does the data found by the prosecution automatically get shared to the defense?
What if it's not going to be used as evidence by you, but maybe perhaps the defense? How would you know what could necessarily interest the defense? It seems a prosecutor could argue that they had no idea these images they saw would ever be considered evidence. Why bring them up? This just smells retaliatory, though.