Google catches pedophile through his Gmail, raising questions about scope of scanning

Google(s goog) is taking on the role of digital vigilante, flushing out creeps and handing them over to the police to capture. While most people would probably agree with Google’s actions, some will wonder how exactly the company is doing this — and where this will all stop.
In case you missed it, the issue came up in Texas last week after Google alerted police that 41-year-old  John Henry Skillern was distributing explicit photos of a young girl through his Gmail account: “I can’t see that information, I can’t see that photo, but Google can,” detective David Nettles told Houston news outlet KHOU last week, following the arrest of Skillern, a Denny’s cook and registered sex offender.
According to Nettles, Google detected Skillern sending the photos to a friend and tipped off police, who then obtained a warrant that led them to find child porn images on Skillern’s phone and tablet.
The arrest puts a spotlight on how Google monitors the contents of its users’ accounts. While the company has long informed Gmail users that it scans their messages in order to show them relevant advertisements, it has never said it scans Gmail for child pornography.
On Monday afternoon, a Google spokesperson provided new details about how the process works:
“Sadly all Internet companies have to deal with child sexual abuse.  It’s why Google actively removes illegal imagery from our services — including search and Gmail — and immediately reports abuse to NCMEC.  This evidence is regularly used to convict criminals.  Each child sexual abuse image is given a unique digital fingerprint which enables our systems to identify those pictures, including in Gmail.  It is important to remember that we only use this technology to identify child sexual abuse imagery, not other email content that could be associated with criminal activity (for example using email to plot a burglary).”
This explanation is consistent with speculation by The Telegraph that the company keeps a database of hashed images from police databases, and looks for matches in the pictures people keep on Gmail. In other words, Google appears to be running an automated service to detect child pornography — and not directly snooping on people’s pictures.
And, as Mashable notes, U.S. federal law requires companies, including photo processing shops, to report child pornography if they come across it. This means that Google would have no choice but to turn in Skillern once it knew about the explicit photos.
Still, the moral and legal issues of the Skillern case are not cut and dry. While most people would probably be okay with email scanning to stop the spread of child pornography, there is still the question of how far such scanning should go. Should Google and other internet providers also monitor users’ accounts in order to alert authorities about possible evidence of other crimes like fraud or illegal narcotics?
It’s an interesting issue, and one that might come up in court if Skillern decides to challenge the evidentiary basis of his arrest.
This story was updated at 6pm ET to include the explanation from the Google spokesperson.