Federal law enforcement agents have been using warrantless cell-tower locational tracking of criminal suspects in the wake of the Supreme Court's ruling 18 months ago that they need probable-cause warrants from judges to affix covert GPS devices to vehicles.

But the law on cell-site locational tracking is all over the books, with judges offering mixed rulings on whether warrants are needed. While dozens of lower courts have ruled on the issue, only two appellate courts have. All of which means some suspects are being convicted based on locational data of what towers their cell phones are pinging, and others are not, because some courts are requiring warrants.

"Only a few courts of appeal have considered this, although a number of lower courts have. They've been all over the map," said Nathan Wessler, an American Civil Liberties Union staff attorney.

The legal crossroads comes as a record number of Americans are embracing mobile phones, which are a de facto style of tracking device consumers willingly place in their pockets and purses. As of December, there were 326.4 million wireless subscriber accounts, exceeding the U.S. population, responsible for 2.30 trillion annual minutes of calls, according to the Wireless Association.

The brouhaha essentially is legal déjà vu all over again.

Consider that, until the Supreme Court ruled in the GPS case last year, the lower courts were mixed on whether the police could secretly affix a GPS device on a suspect's car without a warrant.

And now the latest warrantless crime-fighting method of choice is equally up in the air. The issue has never been squarely addressed by the Supreme Court, and the dispute isn't likely to be heard by the justices any time soon.

The justices last week rejected an appeal (.pdf) from a drug courier sentenced to 20 years after being nabbed with 1,100 pounds of marijuana in a motor home camper the authorities tracked via his mobile phone pinging cell towers for three days from Arizona to a Texas truck stop.

In that case, the Supreme Court let stand the Ohio-based 6th U.S. Circuit Court of Appeals, which covers Kentucky, Michigan, Ohio and Tennessee. The appeals court ruled that probable-cause warrants were not necessary to obtain cell-site data.

The appeals court last year distinguished the case from the GPS case decided by the Supreme Court. The high court ruled that the physical act of installing a GPS device on a target's vehicle amounted to a search, which usually necessitates a probable-cause warrant under the Fourth Amendment.

"Here, the monitoring of the location of the contraband-carrying vehicle as it crossed the country is no more of a comprehensively invasive search than if instead the car was identified in Arizona and then tracked visually and the search handed off from one local authority to another as the vehicles progressed. That the officers were able to use less expensive and more efficient means to track the vehicles is only to their credit," the three-judge appellate panel ruled 2-1.

Although the Supreme Court set aside a District of Columbia drug dealer's conviction and life term in the now infamous GPS tracker case, the authorities subsequently introduced cell-site data – obtained without a warrant – pinpointing the suspect to drug-dealing locations. The defendant, Antoine Jones, later pleaded guilty in a deal that netted him a 15-year prison term.

All the while, privacy advocates are awaiting a decision from the 5th U.S. Circuit Court of Appeals in which three lower-court rulings are at stake. The case involves unidentified suspects in which the lower court said "compelled warrantless disclosure of cell site data violates the Fourth Amendment."

The government argued that a mobile-phone company may disclose historical cell-site records created and kept by the company in its ordinary course of business, where such an order is based on a showing of "specific and articulable facts" that there are reasonable grounds to believe that the records sought are relevant and material to an ongoing criminal investigation. What's more, in both the GPS case and in the cell-site litigation, the government maintains that privacy does not exist in public places.

A court warrant, on the other hand, requires the higher probable-cause standard under the Fourth Amendment.

The 5th Circuit sets law in Louisiana, Mississippi and Texas.

To be sure, some of the rulings on the topic have nothing to do with a suspect's physical locational privacy whatsoever, and instead focus on the so-called "business records" element.

Last year, U.S. District Judge Richard Bennett of Maryland declined to suppress evidence that Aaron Graham and Eric Jordan were allegedly involved in a string of Baltimore City fast-food restaurant robberies. They were arrested in connection to one robbery, and a 7-month historical look of their phone records placed them on the scene when other restaurants were robbed, the authorities said.

Bennett ruled: (.pdf)

For the following reasons, this Court concludes that the Defendants in this case do not have a legitimate expectation of privacy in the historical cell site location records acquired by the government. These records, created by cellular providers in the ordinary course of business, indicate the cellular towers to which a cellular phone connects, and by extension the approximate location of the cellular phone. While the implications of law enforcement's use of this historical cell site location data raise the specter of prolonged and constant government surveillance, Congress in enacting the Stored Communications Act, has chosen to require only 'specific and articulable facts' in support of a government application for such records.

That decision is on appeal with the 4th U.S. Circuit Court of Appeals, which covers Virginia, West Virginia, North Carolina and South Carolina.

The ACLU, Electronic Frontier Foundation, Center for Democracy & Technology, and National Association of Criminal Defense Lawyers urged the circuit court in a legal filing days ago to set aside the locational data because the authorities did not have a warrant.

"The government's acquisition of Defendants' comprehensive cell phone location information without a warrant violates the Fourth Amendment," the groups argued. (.pdf)

The case has yet to be argued.

The only other appellate court to rule on the issue is the 3rd U.S. Circuit Court of Appeals, which said in 2010 that the lower courts have the option to demand a warrant for cell-site data. The court covers Delaware, New Jersey and Pennsylvania.