AUGUSTA — Interests of privacy protection and effective law enforcement collided Wednesday as a bill to restrict “geo-tracking” of people through their cell phones received a committee review in the State House.

The Judiciary Committee held a hearing on Assistant Senate Republican Leader Roger Katz’s bill that would require police to get a court-approved warrant to obtain location information from a cellphone or other electronic device.

The bill does include exceptions, such as using a cell to locate a lost person or, when there’s an imminent threat of serious physical injury or a threat to national security. Katz’s bill is a priority for civil libertarians.

Katz, of Augusta, told the committee that technology has leapt ahead of the 1986 federal law in addressing technology that can spot the location of anyone who carries a cellphone.

“Whether we like it or not, a record is being created on where we are day and night,” said Katz. “Technology has gotten ahead of the law here.”

The American Civil Liberties Union’s Maine chapter warned that advancing GPS technology and a demand for greater cell tower density mean government agents are increasingly able to construct detailed and precise portraits of individuals’ lives and movements.

The ACLU also said that while some police departments around the country get warrants before obtaining an individual’s present or historical location information, there is no statewide standard in Maine.

Geo-tracking is “an extraordinarily powerful surveillance tool,” the ACLU’s Zachary Heiden said.

But the head of the state attorney general’s criminal division, William Stokes, said cellphone tracking technology is also a crucial tool in cracking some criminal cases, including homicides.

In one such case, involving 22-year-old murder victim Christina Fesmire, of Lewiston, investigators might not have been able to persuade a judge that cellphone locator was relevant if the proposed privacy law had been in effect. But cell movements were used and Fesmire’s killer, Buddy Robinson of Lewiston, was convicted of murder last November.

“If law enforcement is required to obtain a search warrant in every case in which location information is requested, this valuable investigative tool may become unavailable in most cases,” Stokes told the committee.

Stokes said there are also cases in which cell tower location information provides an alibi to an innocent person. He also took issue with Katz’s claim that the 1986 federal law has fallen behind technology, saying it effectively addresses privacy concerns.

“I haven’t heard of any law enforcement agencies sitting around snooping on people,” said Stokes. He said most investigators are too busy with open cases to randomly track people