But he added that his interpretation, as a prosecutor, was that intent to simply enter a system might imply responsibility for resulting damage. "If he knew this virus was there, if he helped it get there, if he allowed it to get within a certain computer system" that would constitute responsibility, the Florida prosecutor said.

"The fact that it grew beyond expectations is unfortunate but it does not necessarily negate his guilt," he said.

Responsibility for a program's unexpected performance turns on subtle points of torts law, said a writer with the Journal of Law and Technology at Georgetown University.

"They're calling [Sudduth and Graham] in not necessarily for their expertise, I think, but to establish whether Morris had the intent to infect federal computers, or was he reckless enough [to allow it and was he expert enough," said George-town law student and technology writer Robin A. Meltzer.

"If Morris knew that 95 percent of what he intended to do was harmless, but if he knew there was a risk [in the program running awry] and did it anyway," that might imply guilt, she said.

"In other words, how smart is this guy, should he have known?"

Meltzer added, though, "viruses are an unexplored area--there are no cases, there may be a little out there but it's all less than two years old. They're just becoming big news now."