On the flip side, if they illegally discover evidence but can prove an alternative, legal, way it could be discovered it becomes admissible. That's sometimes why they do it.
Alec Baldwin got off because of screw-ups like this. Seems like when there's a high profile case, all the big shots who normally don't do any work all want to jump in and be involved. And then make stupid mistakes because they don't have any real experience because they're normally too important to work a case.