I have had great success with this defense and this is the primary defense to child pornography distribution in my opinion. It may require the defense to more or less admit possession (or not defense against it). Because the distribution must be knowing, the defense can argue that the defendant had no idea how the program worked and thus, did not know that anyone else could download it from them. This is where the client giving a statement can actually help as the State may feel compelled the play the statement to secure a possession conviction. Without such a statement, the defense will be forced to testify if this defense is to be used. Of course, if the defendant didn’t give any statement, then other defenses may be considered over this one which would prevent the defendant from testifying. Thus, while not limited to such a fact pattern, this defense may be best used where the defendant’s statement to the police already supports this defense.
However, the defendant’s computer expertise may be used against him to show that this defense is unlikely. I worked on an appeal where the defense made a bad argument using this theme only to have the State paint the defendant as a super genius with his custom built computer. The defense attorney, not familiar with a lot of technological issues, failed to adequately prepare for and respond to this counter attack. There are a number of evidence issues that can be used to argue against the introduction of such evidence and it should be fought at all costs.