On Wednesday, July 6, 2011, the Connecticut Supreme Court reversed a former karate instructor's conviction of risk of injury to a child. (The Hartford Courant, July 7, 2011).
The reason is that the prosecutor read an email on the accused computer's that was confiscated by the police. The email was intended for his lawyer which, of course, falls under the Privileged Communications Doctrine. The prosecutor stated that his reading it did not injure the defendant. You can say anything you want but it doesn't work that way.
The court wouldn't merely declare a mistrial as the next prosecutor would read the record about the email which would taint his case also.
Another area that cannot be brought up in court is Work Product. As a former Private Investigator working for attorneys I could not be subpoened to testify on the information I obtained.