"Say a murder occurs on a particular street with an estimated time of death between 2 and 4 AM. Local law enforcement would have an obvious interest in compelling cell phone companies to turn over the records of every cell phone that moved in and out of the area between those two time periods. At rush hour, this kind of information would be useless — but if the cell phone network data shows a device in the same approximate area as the murder suddenly leaving the area at a high rate of speed, that cell phone owner is a potential suspect."
This similar to how CCTV is used in the UK. There is apparently one camera for every eleven people [0]. The difference is the majority of it is owned by private businesses though. Public CCTV is usually run by local councils which are independent from the police. If the police want to get any of this footage, and use it to prosecute, they need to get a court order or subpoena.
> Public CCTV is usually run by local councils which are independent from the police. If the police want to get any of this footage, and use it to prosecute, they need to get a court order or subpoena.
I think you're wrong here. In Westminster, where I live, the police just ask for it and get it. Last month I witnessed a street brawl outside where I live, the police already had CCTV before they were on the scene; it was 4am on a Sunday morning, unlikely a judge would issue a warrant at that time. Also I know places like McDonald's will just hand it over to the police when asked if in connection with a criminal investigation.
This similar to how CCTV is used in the UK. There is apparently one camera for every eleven people [0]. The difference is the majority of it is owned by private businesses though. Public CCTV is usually run by local councils which are independent from the police. If the police want to get any of this footage, and use it to prosecute, they need to get a court order or subpoena.
[0] http://www.telegraph.co.uk/technology/10172298/One-surveilla...