Child Pornography found on a corporate computer

If Child Pornography is found on a corporate computer, what should an employee avoid doing? What should a corporate computer, e-mail and Internet user policy contain? Do you think that chain of custody places an undue burden on investigators of crime scenes? Why or why not? Why should the qualifications of potential witnesses be evaluated? What happens when attorneys fail to do so? Are deleted files ever really gone? Why or why not?