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How tech tracks missing people

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 (REUTERS/Kim Hong-ji)

The case of missing Oregon mom Jennifer Huston has shone a spotlight on technology’s crucial role in locating missing people -- as well its limitations.

While cellphone location technologies can quickly find people, the trail effectively ends when a device is out of power.

Communications expert John B. Minor, who is based in Odessa, Texas and who has assisted in suspected murder cases and attempts to locate lost hikers, describes the scenario as a race against time. “If the battery is exhausted, there is no general tracking,” he told FoxNews.com.

Huston, a 38-year-old mother of two, was last seen on a surveillance camera leaving a gas station in the Portland suburb of Newberg on July 24, prompting a massive search.

Capt. Jeff Kosmicki of the Newberg-Dundee Police Department told FoxNews.com that the last cellphone tower pinged by Huston’s phone was north of the gas station. Her phone shut off at approximately 6.35pm, although investigators don’t know if the battery died or the phone was turned off.

Before a phone is shut off there are a number of ways for networks and law enforcement to locate someone. James Tagg, chief technology officer of mobile network Truphone, which has its U.S. headquarters in Raleigh Durham, N.C., told FoxNews.com that network cell towers, GPS and WiFi all can help.

“In simple terms, cell phones, as the name suggests, connect to a cell,” he explained, in an email.  “A mobile operator always knows which ‘cell site’ you are using and this gives them a rough idea of your location.”

Networks know how far each user is from a cell tower and use data from other nearby towers to ‘triangulate’ a person’s location.

The emergence of high-speed communication technologies such as 3G and 4G has made this technique even more effective. “The newer technologies are more accurate,” Tagg said. “The faster you transmit, the more accurate your timing must be and therefore the better the triangulation.”

GPS technology, widely used in modern phones, is useful, particularly when combined with cell tower triangulation. “Sometimes your cell phone cannot see the satellites and sometimes you (are in an area where you) can only be seen by one [cell] tower or because you are in downtown New York and the signal is bouncing off tall buildings,” wrote Tagg. “Put both techniques together and you are statistically better off.”

Wi-Fi can also help in searches, and Tagg noted that Wi-Fi access points are mapped to precise grid references. However, this information is usually not known to a mobile operator, according to Tagg, but it can be requested by applications on your handset.

Despite the technologies available, the search for Huston has been hampered by red tape. On Thursday, Kosmicki told FoxNews.com that investigators are unable to obtain medical records and cel lphone tower information because there is no evidence of a crime.

Minor told FoxNews.com that, in searches for missing people, law enforcement will often request a “tower dump” from network providers - essentially logs that track each phone’s serial number. “There is passive information maintained in these logs,” he said, noting that the phone does not need to be making a call to be tracked.

Despite all the location techniques available, though, the issue of battery life remains a massive challenge. Investigators can find a location and even the direction a person is travelling, right up to the point when the battery dies. After that, however, their task becomes much more difficult.

Tagg told FoxNews.com that the only technology still functioning in certain phones after the battery dies is Near Field Communication (NFC), which can be used for mobile payments. “Even if you cell phone is dead you could still buy a coffee or gain entry to your office using NFC technology,” he said. “When you do this, the bi-product is you report location as you do so.”

However, Tagg said he is not aware of any service which currently aggregates this information.

Minor believes that the development of longer-lasting batteries will boost future efforts to find missing people. The expert highlights, in particular, recent research at Stanford University that could significantly extend the life of cell phone batteries.

“We need longer battery life,” he told FoxNews.com. “If we had longer battery life and you go missing, there’s a much better chance that you will be located.”

Follow James Rogers on Twitter @jamesjrogers