their variabilities. For these same reasons, extra care must be given to the way in which the analyses are presented in court. The uncertainties associated with bloodstain pattern analysis are enormous.
The analysis of digital evidence deals with gathering, processing, and interpreting digital evidence, such as electronic documents, lists of phone numbers and call logs, records of a device’s location at a given time, e-mails, photographs, and more. In addition to traditional desktop and laptop computers, digital devices that store data of possible value in criminal investigations include cell phones, GPS devices, digital cameras, personal digital assistants (PDAs), large servers and storage devices (e.g., RAIDS and SANS), video game consoles (e.g., PlayStation and Xbox), and portable media players (e.g., iPods). The storage media associated with these devices currently fall into three broad categories. The first, magnetic memory, includes hard drives, floppy discs, and tapes. The second, optical memory, includes compact discs (CDs), and digital versatile discs (DVDs). The third, electrical storage, includes USB flash drives, some memory cards, and some microchips. These items are the most commonly encountered in criminal and counterintelligence matters, but laboratories have been asked to examine such items as scuba dive watches in death investigations and black boxes in aircraft mishaps.
The proliferation of computers and related devices over the past 30 years has led to significant changes in and the expansion of the types of criminal activities that generate digital evidence. Initially, computers were either the weapon or the object of the crime. In the early days, most computer crime involved manipulating computer programs of large businesses in order to steal money or other resources. As computers became more popular, they became storage containers for evidence. Drug dealers, book makers, and white collar criminals began to keep computerized spreadsheets detailing their transactions. Digital cameras and the Internet have made child pornography increasingly available, and computers act as a digital file cabinet to hold this contraband material. Finally, digital media have become witnesses to daily activities. Many individuals have two cell phones with text messaging and/or e-mail capability, several computers, a home alarm system, a GPS in the car, and more; even children often possess some subset of these items. Workplaces use magnetic card readers to permit access to buildings. Most communication involves some kind of computer, and by the end of each day, hundreds of megabytes of data may have been generated about where individuals have been, how fast they got there, to whom they spoke, and even what was said. Suicide notes are written on