The acquittal of Mr Seán Foley of knowingly possessing child pornography could pave the way for a succession of so called "trojan horse" or "cookie" defences in similar legal cases.
Trojans and cookies are small pieces of software code that can attach themselves to a user's computer without his or her knowledge. In its most benign form, this software can help a website remember a particular user. But it can also spy on a computer user's online activity, or worse, redirect their Internet settings to automatically access offensive or illegal child pornography on the web.
Typically, music file sharing networks, pornographic websites and online gambling websites harbour this type of rogue software.
Computer experts estimate that most home computers have some form of rogue software installed on them without their owner's knowledge. But most of these softwares would not install child pornography on a user's machine.
Mr Foley had told gardaí that he had never seen the images recovered from his computer and that he was aware that websites could send a "cookie" to the computer's hard drive or "leave a fingerprint". If the trial had proceeded, it is likely his legal defence would have centred around the so-called "trojan horse defence".
Last year a British court threw out a similar case against Mr Julian Green, who was accused of illegally possessing images of child pornography. It agreed with his defence that the illegal material got on his computer via a trojan programme that installed itself during innocent net surfing.
"In this case it was possible to clearly identify how the trojan infection had affected the computer," said Mr Tony Dearsley, computer investigations manager for the data and forensics company Vogon International.
It is also possible to determine that particular images had been viewed by a user and exactly when a trojan had become installed on a computer.
Mr Dearsley said he was also aware of cases where people had deliberately installed trojans on their computers to provide excuses for illegal activity.
While experts' investigations of computers are needed to assist in the fight against child pornography, innocent victims of "trojans" will require similar diligence from prosecutors to avoid huge damage to their reputation.
Mr Robin Fry from the British law firm Beachcroft Wansbroughs said yesterday the Green case and the Foley case would have wider importance:
"The case will have ramifications in the downloading area where the record and film industries are increasingly targeting the file-sharers," he said. But "no-one should be convicted of dangerous driving if your steering wheel and gear stick have been wrenched from you. But that's what a Trojan Horse can do. You should only be liable if you've direct control of the equipment you're using."