In 2015, there were more than 7 billion mobile cellular subscriptions worldwide, up from less than 1 billion in 2000, says International Telecommunication Union (ITU). The world is witnessing technology and user migration from desktops to mobile phones. The following graph sourced from statista.com shows the actual and estimated growth of smartphones from the year 2009 to 2018.
Growth of smartphones from 2009 to 2018 in million units
Gartner Inc. reports that global mobile data traffic reached 52 million terabytes (TB) in 2015, an increase of 59 percent from 2014, and the rapid growth is set to continue through 2018, when mobile data levels are estimated to reach 173 million TB. Smartphones of today, such as the Apple iPhone, the Samsung Galaxy series, and BlackBerry phones, are compact forms of computers with high performance, huge storage, and enhanced functionalities. Mobile phones are the most personal electronic device that a user accesses. They are used to perform simple communication tasks, such as calling and texting, while still providing support for Internet browsing, e-mail, taking photos and videos, creating and storing documents, identifying locations with GPS services, and managing business tasks. As new features and applications are incorporated into mobile phones, the amount of information stored on the devices is continuously growing. Mobiles phones become portable data carriers, and they keep track of all your movements. With the increasing prevalence of mobile phones in peoples' daily lives and in crime, data acquired from phones become an invaluable source of evidence for investigations relating to criminal, civil, and even high-profile cases. It is rare to conduct a digital forensic investigation that does not include a phone. Mobile device call logs and GPS data were used to help solve the attempted bombing in Times Square, New York, in 2010.
The details of the case can be found at http://www.forensicon.com/forensics-blotter/cell-phone-email-forensics-investigation-cracks-nyc-times-square-car-bombing-case/.
The science behind recovering digital evidence from mobile phones is called mobile forensics. Digital evidence is defined as information and data that is stored on, received, or transmitted by an electronic device that is used for investigations. Digital evidence encompasses any and all digital data that can be used as evidence in a case.