Since the early 1980s cell tower information has been used to provide evidence in courts across America to defend and prosecute criminals. They are not an exact science and have their flaws but, like all technology, they are getting better.
For those of you not schooled in the world of cell towers, please remember this is merely a tool and not a science. Cell towers, typically, have three sides: Alpha, Beta and Gamma. A tower is essentially nothing more than a line-of-sight instrument and is computer controlled to “hand off” a call as it passes from one tower’s radius area to another. Inner-city towers are typically good for up to one to two miles; however, the towers’ cell signals can be blocked by tall buildings, more so by a newer, predominantly “steel” type of skyscraper.
The most important factors to understand when reading cell towers are the traffic, the pitch of the tower, and the landscape or terrain. For example, it would not be uncommon for a call in San Jose to cross the San Francisco Bay and get picked up an Oakland or East Bay tower, some 20 miles away, again, depending on the traffic.
There are temporary situations with tower traffic that are not addressed by the cellular companies, such as when a major league team is playing a game and people are sitting in traffic waiting to get to a ballpark. The towers in the immediate area will get overloaded, and the computers will do their best to seek and connect to a reasonably close tower. With no interference, again, this signal could travel a great distance, and reading the tower reports can be confusing, making the cell tower traffic reports that much more important.
Other examples of terrain are cell towers in the desert or on the Great Plains. The traffic from Los Angeles to Las Vegas is bumper to bumper on any given weekend, and I can say with complete certainty that the majority of Angelinos sit on their phone the vast majority of time during this trip. The cost of placing towers every few miles would be earth shattering, so the pitch of the towers, simply put, is turned toward the sky to cover a greater distance. Thus, the towers are spaced between 30 and 40 miles apart, again, based on the terrain.
SCAMP or traffic reports are what the cell companies use to monitor daily tower activity by the engineers at all cell companies. If they find the need to alter the pitch to send and receive calls from a greater distance or add new towers, their job is to keep the customers happy. Dropped calls are tantamount to unhappy customers and dropped business.
Within the past few years, the phone companies have realized the importance of these tools. They are good for putting a person in a general location, again, with the understanding that all the factors fall into play. If the traffic is not overwhelming, the signal strength is strong and the handoff is consistent from an originating tower, you can place someone in a major metropolitan setting within a range of one to two miles.
Recently, in a murder case in San Jose, California (State of California v. Bulos Zumot), the cell towers were used to follow the defendant from a specific location where he was positively identified some 30 miles up the freeway to the location of the homicide. The prosecution brought in an “expert” who used the towers to explain and show the defendant’s path of travel from San Jose to Palo Alto and subsequently, in their opinion, to the scene of the crime. And of course, all this activity is time-stamped.
It might have been clear and convincing evidence had it not been for the flaw established by the defense. Although it is not known to be true of all companies, it was established in this case that, according to AT&T records, if a call is placed from one cell phone to another and the call goes into the recipient’s mail box, the AT&T call shows as connected. However, the tower reading will reflect the tower from which the call originated. In this particular case, the defendant’s private investigator noted that a call was placed on an unrelated day a week before the incident when the defendant was, again, known to be in the San Jose area.
The defendant’s cell tower records showed an incoming call placing the defendant near a tower in Lahaina, Maui, and within nine minutes of that call, a previous call placed the defendant in Palo Alto. Because of this “flaw” in AT&T’s system, by all rights, the defendant received the first call from a tower on the island of Maui, some 3,000 miles away. The prosecution’s expert was then asked under oath, “Can you get from San Jose to Maui in nine minutes?” Again, their “expert” replied, “It depends on your mode of travel.” A valuable lesson in how not to choose an expert.
This has become the easiest aspect since the inception of cell phones. When you subpoena cell records, you also subpoena an engineer, not only to lay the foundation but also to interpret your information. Ironically, at least in criminal matters, these experts are free. Yep, free. They are engineers familiar with their own towers, they have no interest in either party and are not stupid enough to think you can get from Maui to San Jose via the Starship Enterprise.
There is also a type of search called “pinging.” Where law enforcement once had to obtain a search warrant to “ping” a cell phone by using cellular company equipment, they now have tracking devices able to actively “ping,” or send a signal to, a cell phone and determine its exact location, on their own.
The truth of the matter is, it can take up to about 12 pings to actually close in on the exact position of the phone. Regardless, because of the importance of cell tower information, cell companies have increased maintaining their tower records from what used to be 45 to 55 days to, now, between two and four years.
More important, it is nice to know that you can send a preservation letter to the companies if your civil or criminal matter has not yet been filed. The companies are very good about gathering and maintaining your data; they just won’t turn it over without a proper subpoena.
There are companies that advertise they can ping a phone. I have never tried to use these services and have advised clients against it, although I have invited them to contact directly the people claiming to have this ability. The law enforcement agencies that do this are trying to locate a “suspect” after the commission of a crime and have a legitimate use. Civil clients are typically trying to locate a spouse, and without complete certainty, personally, I would not jeopardize my license by getting involved in such a search.« Back to Blog