Broader access to people’s metadata of their past use of telecommunications services has been a divisive topic of debate over the last twelve months in Australia. The argument has waged over the right to privacy, metadata misuse and the need to stop criminals but with little concern about justice.

To date in Australia law enforcement has had easy access to one form of metadata called “call charge records” or CCRs used for billing for telephone calls. CCRs that identify both the caller and the called party indicate the start time and duration of every call made. But in the case of mobile calls, CCRs contain location information on where the mobile either made or received a call. The information in the CCR is termed the “cell ID” that uniquely identifies the cell site on a base station that was used at the beginning of the call. Our police routinely access such data on request from the relevant Telco to determine the approximate location of a suspect’s mobile at the time of a call to support criminal investigations and subsequent prosecutions.

“In some cases such unchallenged ‘evidence’ has been in my opinion highly prejudicial of the case.”

However, in many cases when such information is presented in court as evidence of location, “much is made of too little” and injustice is the result. The TV series CSI would have you and the bulk of the criminal establishment believe such information was like a finger print but the reality is more complex and demands caution.

Knowledge of the particular cell site used for a mobile call of interest does provide a clue to the mobile’s location but the degree of approximation is highly variable depending on the particular radio network design and many other factors. In mobile systems cell coverage from adjacent cells overlap and a mobile does not necessarily use the closest cell site. Two mobile users on the same network standing right next to each other can register on different cell sites.

Since becoming lured into the high profile Phung Ngo case in 2008 (see video above), I have been an expert witness in over a dozen cases. In some of these cases many pages of CCR data and software prediction maps are accepted by our courts as evidence of location in connection to an alleged crime. In some cases such unchallenged “evidence” has been in my opinion highly prejudicial of the case. Only recently in an Australian court has such material been contested as not meeting the standard required of expert evidence. The judge in this case at least required measurements of the base station coverage predictions.

The misuse of mobile phone metadata is not unique to Australia. Only recently have I become aware that the United States justice system is now questioned the abuse of metadata propagated by their premier law agency the FBI! Compared to Australia access to Call Charge Data in the US is more stringent and the FBI do often actually conduct measurements at the alleged cell phone sites usually not required by our courts!

Against this context, envisage the explosion of misinformed inferences from such data if made available to some 61 government agencies often for civil consideration now under consideration by the Australian government. It At least in our courts there is the opportunity for the interpretation of metadata can be contested by informed litigants.