According to a recent survey conducted by the American Civil Liberties Union (ACLU), many US police departments use cell phones, often without court orders, to find suspects and investigate criminal cases. The ACLU survey indicates that "the overwhelming majority of law enforcement agencies that responded engage in at least some cell phone tracking." The results of this survey were posted on Yahoo! News site.

The survey shows that "most law enforcement agencies that responded engage in cell phone tracking for investigative purposes. Even those that have not tracked cell phones in the course of a criminal investigation have tracked cell phones in emergencies, for example to locate a missing person."

As per the study, the use of phone tracking, using GPS or other technology to locate people through their cell phones, is a murky legal area. According to the study, the US Supreme Court has held that the use of GPS devices placed by police on a suspect's car constitutes an "unreasonable search" under the constitution. Despite the law, cell phone tracking is still making its way through the courts, per ACLU study reported on Yahoo! News site.

In fact, according to the report, several members of Congress have introduced bills calling for "location privacy" to be respected by police, except in cases of emergency.

For this study, ACLU surveyed more than 200 law enforcement agencies. The survey shows disturbing results, with few police departments seeking warrants and unclear or inconsistent legal standards, depending on the jurisdiction, wrote Yahoo! News.

The Yahoo! News report quoted ACLU attorney Catherine Crump as saying, "What we have learned is disturbing. The government should have to get a warrant before tracking cell phones. That is what is necessary to protect Americans' privacy, and it is also what is required under the constitution." "The fact that some law enforcement agencies do get warrants shows that a probable cause requirement is a completely reasonable and workable policy, allowing police to protect both public safety and privacy."