A PROSECUTOR'S JOB IS, and has always been, to seek justice--for victims, families, communities, and the accused. Today, new types of evidence are helping law enforcement and prosecutors conduct more thorough and accurate investigations. Though the evidence used years ago continues to play a valuable part in a criminal case, the improvements in science and technology are enabling police and prosecutors to solve more crimes more reliably than ever before.
The following is an overview of the forms of evidence increasingly used by prosecutors over the past several decades, including DNA, surveillance cameras, computers, cell phones, GPS, social media, and police body cameras. Each section provides a brief history of the technology, as well as a summary of the technology's current capabilities. The article also addresses emerging technologies that are likely to have an increasing impact on criminal investigations, including Next Generation DNA Sequencing, drones, facial recognition, and gunshot detection. Finally, the authors address challenges related to the increased use of cloud storage and the phenomenon of "going dark", which is limiting law enforcement access to smart phone and other digital evidence.
Though this article occasionally alludes to legal issues, it is not intended to address the legal standards for acquiring evidence and introducing it in court. Case examples are given to illustrate how the evidence has proven helpful to prosecutors and law enforcement. Some examples are based on high-profile cases, while others are based on reports from prosecutors throughout the country.
In May of 2013, a Colorado man fails to show up to work. Concerned, the man's boss visits his house, where the man's roommate refuses to let the boss enter. The boss contacts the police, who launch a missing person investigation.
Using cell tower technology, police are able to approximate the missing man's location in the hours leading up to his disappearance. Cell phone data also suggests that the roommate's phone traveled to and from a remote area where, three weeks later, the man's body is discovered. On the day of the disappearance, bank ATM records show repeated mistaken entries of the victim's PIN before someone withdrew a large sum of money, and a bank surveillance video shows the victim's car present at the time of the transaction. That same day, surveillance video at a gas station shows the roommate driving the victim's car and wearing his jacket. Another supermarket surveillance video from the same day shows the roommate purchasing bleach.
Several decades earlier--without surveillance video, cell phone records, and electronic bank records --this crime might have gone unsolved. With no eyewitnesses and no one to contradict the roommate's alibi, prosecutors would have had difficulty filing charges and securing a conviction. Instead, armed with all of this evidence, prosecutors were prepared to bring murder charges against the victim's roommate with or without a body. After a twelve-day trial and one day of deliberations, jurors convicted the roommate of first-degree murder and sentenced him to life in prison. (1)
A prosecutor's job is, and has always been, to seek justice--for victims, families, communities, and the accused. Today, new types of evidence are helping law enforcement and prosecutors conduct more thorough and accurate investigations. Though the evidence used years ago continues to play a valuable part in a criminal case, the improvements in science and technology are enabling police and prosecutors to solve more crimes more reliably than ever before.
NEW FORMS OF EVIDENCE
The following is an overview of the forms of evidence increasingly used by prosecutors over the past several decades. Each section provides a brief history of the technology, as well as a summary of the technology's current capabilities. Though this article occasionally alludes to legal issues, it is not intended to address the legal standards for acquiring evidence and introducing it in court. Case examples are given to illustrate how the evidence has proven helpful to prosecutors and law enforcement. Some examples are based on high-profile cases, while others are based on reports from prosecutors throughout the country. (2)
In 1953, researchers identified DNA (deoxyribonucleic acid), the chemical source of genes. (3) In the 1960s and 1970s, the field of molecular genetics emerged as scientists learned to "read" DNA. Forensic DNA testing began in 1985. (4) Three years later, Tommie Lee Andrews became the first person in the United States to be convicted due to DNA evidence in his rape trial. DNA from semen found in the victim matched his blood sample, ensuring his conviction. (5) In the years that followed, DNA emerged as "the most reliable physical evidence at a crime scene, particularly those involving sexual assaults." (6)
DNA databases are now widespread. "All 50 states and the federal government have laws requiring that DNA samples be collected from some categories of offenders." (7) Additionally, twenty-three states require all convicted felons to provide DNA samples. (8) State and federal laws determine the types of criminal offenders required to submit DNA samples to each database.
The FBI manages the Combined DNA Index System (CODIS), which supports state criminal justice DNA databases and software, and the National DNA Index System (NDIS), which links state and federal databases together, allowing efficient comparison of DNA profiles.
State DNA databases include at least two categories of profiles: samples collected directly from known offenders or detainees (offender profiles), and those gathered at crime scenes (forensic profiles). (9) By collecting and cross-referencing samples, investigators can solve crimes more effectively than ever before. For example, a sample collected at a crime scene might match the profile of a known offender. Likewise, a sample collected from a suspect could match biological material from an old crime scene, allowing investigators to solve a cold case. As of May 2015, NDIS contains nearly twelve million offender profiles and more than 600,000 forensic crime scene profiles. (10)
DNA evidence must be collected, handled, and stored using sterile, environmentally controlled methods. Using cell samples (e.g., hair follicles or blood cells), technicians isolate, identify, and compare certain characteristics of an individual's genetic structure. (11 )Testing is verified using "principles of statistics and population genetics to give statistical significance to the DNA match, by indicating the statistical frequency with which such matches might occur in the population. (12)
Advances in DNA analysis techniques have reduced the required body fluid or tissue sample size, allowed for extraction of DNA from degraded or mixed samples, and cut down the time needed to create a DNA profile. (13) For example, a process known as DNA amplification allows scientists to test degraded samples by finding and replicating the sample's untainted regions and thus generate more usable amounts of DNA. (14) Rapid testing is under development to enable creation of a profile compatible with DNA databases in one to two hours. (15)
A recent murder case in Virginia is an excellent example of how DNA collection can prove useful. In 2009, a man was fatally stabbed and robbed on his way to work. Police swabbed the man's pockets, which had been turned inside out during the robbery, and created a new DNA profile in the state's crime scene database. The profile did not initially match any known offender, but police were able to solve the crime a year later when the profile matched a man added to the offender database. From the DNA, the police identified the suspect, who confessed to the crime and testified against his accomplice. Neither of the perpetrators had any ties to the victim and, without DNA evidence, the murder almost certainly would have remained unsolved.
DNA evidence is particularly useful in solving cold cases involving rape, because rape kits collected from victims often provide DNA evidence from the attacker. Forensic profiles created from the rape kit can be stored for decades, allowing law enforcement to cross reference forensic profiles with new offender profiles added to the database. A 2015 Michigan case demonstrates how effective DNA databases can be at solving cold cases. A man was convicted of felony drug charges and, pursuant to state law, was required to submit a DNA sample to the Michigan Convicted Offender Database. The DNA sample matched the forensic profile from a 2001 Michigan rape case, as well as profiles from two rape cold cases in Texas from the early 2000s. (16)
Due to the widespread use and sophistication of surveillance technology, it is one of the most common and useful forms of digital evidence available today. Law enforcement officers, business owners, and private individuals have installed surveillance cameras in many places of business, public spaces, traffic lights, and private homes.
Video surveillance was first used in the 1950s, long before the technology was digital. Public surveillance by police departments began in Hoboken, New Jersey, in 1966, and Mount Vernon, New York, in 1971. (17) Improvements in the technology in the eighties and nineties led to its increased use, but the images were low-resolution and grainy, making them difficult to use.
Digital surveillance cameras, which produce clearer, higher-quality images, were first installed on street corners in major urban areas like New York, Chicago, and Washington, D.C. In 2006, Chicago launched Operation Virtual Shield, which linked together a vast network of police and private cameras estimated to number in the tens of thousands. (18) Cameras are now commonplace in less populous cities, as well as in suburban and rural communities throughout the United States. (19) Where...