In the ongoing battle against government eyes prying into every aspect of our digital lives, the United States Supreme Court delivered a victory for personal privacy rights last week.

The ruling forbids warrantless police searches of the contents of arrestees' cell phones, deeming such routine practice unconstitutional. If police want to search the cell phones of people they arrest, they must first get a warrant.

Chief Justice John Roberts, who wrote the landmark opinion, acknowledges that what the Supreme Court has done will impact the ability of law enforcement to combat crime. As he points out, criminal enterprises, like everyone else, use cell phones to communicate and coordinate what they do. And it goes without saying that cell phones can provide valuable incriminating information about dangerous criminals. To which the good judge responds with a succinct: "Privacy comes at a cost."

In making his finding, Roberts rejected law enforcement's view that a search of all data stored on a cell phone is "materially indistinguishable" from a search of an arrested person for physical items, such as weapons or fruits of crime.


"That is like saying a ride on horseback is materially indistinguishable from a flight to the moon," says Roberts.

"Both are ways of getting from point A to point B, but little else justifies lumping them together. Modern cell phones, as a category, implicate privacy concerns far beyond those implicated by the search of a cigarette pack, a wallet, or a purse."

Robert's logic resides in the American constitution, specifically the Fourth Amendment - "the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated...".

The key issue, he says, is "reasonableness". He points out that the Fourth Amendment was a response to the reviled "general warrants" and "writs of assistance" of the colonial era, which allowed British officers to rummage through homes in an unrestrained search for evidence of criminal activity. "Opposition to such searches was in fact one of the driving forces behind the Revolution itself."

Read also: Warrant needed to search phones - US court

Fighting words, but perhaps a little hollow when one considers the American National Security Agency (NSA) and indeed our own security agency, the GCSB, are covertly rummaging through our digital homes on a daily basis.

Glenn Greenwald's No Place to Hide which examines whistleblower Edward Snowden's archive, reveals we now live in a world where "the new collection posture" is to "sniff it all, partner it all, know it all, collect it all, exploit it all, process it all." In this context of dragnet mass surveillance of our digital existence, court sanctioned privacy of one's cell phone data seems almost irrelevant.

But you have to admire the stand, even if it seems King Canute-like.

Roberts notes that modern cell phones are now such "a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy".

At times, his opinion reads as if he's only just realised the world has changed - earnestly telling us the term "cell phone" is misleading shorthand and that actually many of these devices are in fact minicomputers that also happen to be used as a telephone.

"They could just as easily be called cameras, video players, rolodexes, calendars, tape recorders, libraries, diaries, albums, televisions, maps, or newspapers."

The good judge, who writes his opinions by hand and once asked what was the difference between email and pagers, is similarly astonished by the cell phone's immense storage capacity - 16 to 64 gigabytes for the current top-selling smart phone.

"Sixteen gigabytes translates to millions of pages of text, thousands of pictures, or hundreds of videos." Gosh.

Then there are the apps - the average smart phone user has installed 33 apps, "which together can form a revealing montage of the user's life". And cloud computing - "the capacity of internet-connected devices [cell phones] to display data stored on remote servers rather than on the device itself".

Roberts joins the dots and concludes that it's no exaggeration to say that "many of the more than 90 per cent of American adults who own a cell phone keep on their person a digital record of nearly every aspect of their lives - from the mundane to the intimate."

No doubt it's much the same in New Zealand and while we don't have the Fourth Amendment we do have laws to protect our digital privacy - although perhaps not as grounded in history as the Americans.

Our Bill of Rights and Privacy Act afford some protection but our courts have yet to properly test the bounds of warrantless searches of digital data. In general in New Zealand a warrantless search of a portable data storage device is permitted only where the device could potentially hold evidential material relating to the offence for which the warrantless power is exercised. In other words if when you're arrested, the police reasonably think you're a drug dealer they can rummage through your cell phone.

But a recent Supreme Court case shows there is room for more debate.

Here, the issue was the admissibility of evidence derived from the police search of a camera memory card located in the defendant's shirt pocket and that the photographs on the camera memory card were accessed by a police officer some days after the defendant's arrest, without the authority of a search warrant.

The Court of Appeal found the evidence was improperly obtained but then, in a legal back-flip, deemed it admissible under a Section 30 "balancing exercise" of our Evidence Act. Section 30 allows a judge to assess whether the "exclusion of the evidence is proportionate to the impropriety".

This has been criticised as a process that may "permit the personal predilections of judges to masquerade as principle and ... sanction little more than a judicial 'gut check'."

In this instance the Supreme Court decided while the "issue of when a search of a camera card may be undertaken could be seen to be one of general and public importance", the matter would be more appropriately dealt in a post conviction appeal.

So New Zealand courts have yet to catch up with the Americans. Until they do, New Zealanders' privacy expectations regarding their cell phones remain an open book.