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How the RCMP's secret surveillance tools work

RCMP documents disclosed in a recent trial acknowledge that portable surveillance devices, used to target crime suspects, directly impact "innocent third parties" within range — including people dialling 911.

The devices, known as IMSI catchers, mimic cellphone towers and are capable of extracting key identifiers such as the International Mobile Subscriber Identity (IMSI) from nearby GSM phones.


1 A police team turns on its device causing radio waves to emit from an unmarked police vehicle. The machine beckons to phones suggesting it is the strongest cellphone tower in the area.

2 It’s a “hit” – the targeted person’s phone automatically redirects its signal to the police device.

3 The suspect’s phone has unique digital identifiers that are pulled into a database – as are those of phones belonging to innocent third parties. Police can later try to bug the target phone.

4 The police devices can have the side effect of temporarily blocking all new calls – and while 911 calls are supposed to override the interference, up to half the time this does not happen.