In 2013, there were almost as many mobile cellular subscriptions as there were people on earth, says International Telecommunication Union (ITU). The following figure shows the global mobile cellular subscriptions from 2005 to 2013. Mobile cellular subscriptions are moving at lightning speed and passed a whopping 7 billion early in 2014. Portio Research Ltd. predicts that mobile subscribers will reach 7.5 billion by the end of 2014 and 8.5 billion by the end of 2016.

Mobile cellular subscription growth from 2005 to 2013

Smartphones of today, such as the Apple iPhone, 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 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 moves. 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.