An Ontario judge is set to rule on a consumer privacy case that pits telecom companies against police departments.

In July, Justice John Sproat agreed to hear a Charter of Rights challenge brought by Telus and Rogers after they were asked by Peel Regional Police to release cellphone information about thousands of customers as part of an investigation.

Arguments in the case have concluded, and the decision is now under reserve, said a staff member from Sproat’s office, which means that the ruling could soon be made public soon.

The case: In April, Peel police obtained a production order — similar to a warrant — demanding the customer information from all cellphones that accessed 36 cell towers owned by Rogers and Telus during a specific time frame.

Police argue they need the records in order to find a suspect who may be part of the tower dump. Rogers and Telus are challenging the production order, arguing that it violates the Canadian Charter of Rights and Freedoms.

Peel police withdrew the order but the judge decided to hear the case because these kinds of orders are becoming more common.

“The privacy rights of the tens of thousands of cellphone users is of obvious importance,” Sproat wrote in his July ruling explaining why he would hear the case.

“Counsel for Rogers-Telus will be able to identify and argue charter issues that might not otherwise be evident.”

How do police use cellphone data?

Every time you send a text, use data or make a call, your cellphone uses local cellphone towers. Police can go to a judge and ask for all the data collected at certain cellphone towers during a specific time frame in order to scour the information for potential suspects.

For example, if there’s been a series of bank robberies in an area, police could request the cellphone records that have travelled through the towers. They can then look for customers that were in the area around the same time as the robberies and narrow down their list of suspects.

Why does this matter?

Tower dumps cast a wide net. Although they can catch a few criminals, thousands of innocent people also get pulled in, said privacy law expert Frank Addario.

“Everybody’s caught up in it,” he said.

In Canada there is no legislation governing the acquisition of large amounts of data by law enforcement. While private companies must limit the amount of information they collect, police do not have to justify the scope of their requests in the same way.

What do police do with data on people not pertinent to the investigation? How is it stored? Without clear guidelines from lawmakers, judges have had to make rulings ad hoc as telecom providers challenge these production orders.

“Judges have had to make up the laws as they go along,” Addario said.

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Addario said that while everybody gives up some privacy when they use cellphone technology, police surveillance is not something people signed up for.

“You certainly didn’t give that privacy up just because the person who signed up for the Rogers account right after you happens to be involved in criminal activity. That’s not your fault,” he said.

What information was being asked for?

According to Sproat’s ruling, the Peel police production order asked for the name and address of every subscriber making or attempting a communication, the particular cell tower they used and billing information (including credit card and bank numbers).

If both the person initiating and receiving the communication were Rogers (or Telus) subscribers, then information regarding the recipient would also have to be provided.

How many people would be affected by the order?

Rogers and Telus estimate that about 43,000 subscribers would be caught in the time frame of the data dump, amounting to hundreds of thousands of records.

How common are these orders?

In its affidavit, Telus indicated that in 2013 alone, it responded to approximately 2,500 production orders and general warrants. Telus wrote that this production order was the most extensive to date, regarding the amount of customer information affected.

The Rogers affidavit indicated in 2013 alone, it produced 13,800 “files” in response to production orders and search warrants.

With files from The Canadian Press