"The personal privacy implications are pretty clear but so are the law enforcement applications," according to the document, titled "Google Timelines: Location Investigations Involving Android Devices," which outlines the kind of information investigators can now obtain.

The Timeline allows users to look back at their daily movements on a map; that same information is also potentially of interest to law enforcement. "It is now possible to submit a legal demand to Google for location history greater than six months old," the report says. "This could revitalize cold cases and potentially help solve active investigations."

The report was written by a law enforcement trainer, Aaron Edens, and provides detailed guidance on the wealth of historic location information available through Google Timeline and how to request it. A copy of of the document was obtained by The Intercept.