Virtually every aspect of life involves policies, regulations, and laws that help to promote public safety. Public safety, and the rules that go with it, has been a concern for a long time. In the earliest societies it was clear that people would run wild unless certain rules of conduct were created. Some laws evolved from the common agreement of the group's members, while others were handed down by the group's leaders.

Soon after the establishment of rules and laws, methods of enforcement developed. For a long time, enforcement simply meant punishment. Those who broke the laws were often ostracized or exiled from the group, subjected to corporal punishment, tortured, maimed, or even killed. Enforcement of the law was usually left up to the society's leaders or rulers, often through the soldiers who served in their armies. Often these armies also collected taxes, which were used to maintain the army and sometimes to line the ruler's pockets.

Eventually, more organized methods of public safety were developed. In England, for example, early law enforcement officials were considered servants of feudal lords, kings, and other rulers, and their duties revolved around protecting their masters' interests rather than ensuring the public safety. Colonial America followed in England's footsteps and adopted its system of law enforcement.

Cities grew larger during the 18th and 19th centuries, and the need arose for even more organized efforts, since larger cities often meant more crime, riots, and other disorders. The first modern police force was formed in 1829 in London. Cities in the United States organized police forces as well, beginning with New York in 1844. Interstate crimes were placed under federal authority, and various agencies, including the U.S. Marshals Service, the Federal Bureau of Investigation (FBI), the Secret Service, the Internal Revenue Service (IRS), and Customs and Border Protection, were formed to enforce laws across various jurisdictions.

The punishment of criminals changed as well. Beginning in the 18th century, efforts were made to create punishments that were equal to the crime. To deter people from committing crimes, societies began to develop specific punishments for specific crimes. These newer penalties generally called for a period of incarceration. Jails and prisons historically had been used as temporary holding pens before more permanent punishments, such as exile or death, but now became an important feature of these new ideas of punishment. The new prisons hired guards to watch over the prisoners, bring them food, and prevent them from escaping. The first American jails appeared in the late 18th and early 19th centuries. In the 21st century, private prison companies have built prisons or taken over the management of existing prisons for state and local governments. These for-profit companies have raised the concern that they generate an incentive for increasing incarcerations because the more beds that are filled in these systems the more profits that are made. But government agencies are taxed with an overflowing prison system and shrinking budgets, creating the need for these private prisons.

Another feature of protecting the public safety was the detection, prevention, and solving of crimes. Police officers who specialized in these efforts became known as detectives. Much like today, their job was to examine evidence related to a crime in an effort to catch the person or persons responsible. They also were vigilant in trying to prevent crimes and to catch criminals in the act. During the 19th century, the first private detectives and detective agencies appeared. These agencies not only worked to solve crimes against their clients but also offered guard services for people and their property.

Solving crimes also became more and more scientific. As early as 1780, a crime was solved when a suspected criminal's shoes were found to match footprints left at the scene of the crime. Toward the end of the 19th and the beginning of the 20th centuries, modern forensic science techniques were developed. Methods were developed to link fingerprints, bullets, weapons, hair, soil, and other physical evidence found at a crime scene to the crime and the criminal. Laboratories were constructed that were devoted to this work. The Federal Bureau of Investigation's laboratory, established in the 1920s, became the largest and most famed crime laboratory in the world. 

Since the 1980s, DNA (deoxyribonucleic acid) testing, also known as DNA profiling, has evolved to become a critical part of criminal investigative work. The U.S. Department of Justice stated that "DNA can be used to identify criminals with incredible accuracy when biological evidence exists. By the same token, DNA can be used to clear suspects and exonerate persons mistakenly accused or convicted of crimes." DNA profiling is a forensic method of matching DNA evidence to criminal suspects' DNA profiles (obtained as blood and saliva samples) to see if there is a match. In August 2017, the Rapid DNA Act was signed into law. Rapid DNA enables the analysis of DNA samples in about 90 minutes instead of the days and even weeks DNA analysis has taken in the past. This recent law gives law enforcement broader ability to use rapid DNA analysis technology and upload the resulting data into a federal database.

Intelligence operations, that is, the collection and evaluation of information about one's rivals or enemies, have also been a part of our history for a long time. The Central Intelligence Agency (CIA) became responsible for preserving U.S. international interests. The FBI was charged with maintaining the country's internal security. Each branch of the military services also operates intelligence forces.

After the terrorist attacks of September 11, 2001, the Department of Homeland Security was formed under the Homeland Security Act of 2002. This department of the federal government has three main goals: to prevent terrorist attacks within the United States, to reduce America's vulnerability to terrorism, and to minimize the damage from potential attacks and natural disasters.

The rise of the World Wide Web in the 21st century has also led to another forensic science: computer forensics. These experts examine suspects' computers to find evidence of criminal acts. These workers also investigate cybercrimes, or those committed via the Internet. Computer forensics also help to ensure the overall integrity and survivability of network infrastructure. The main goal of computer forensics is to identify, collect, preserve, and analyze data that not only collects but also preserves evidence so that it can be used effectively in a legal case.