Crime scene in the context of "Locked room mystery"

Criminal investigation is an applied science that involves the study of facts that are then used to inform criminal trials. A complete criminal investigation can include searching, interviews, interrogations, evidence collection and preservation, and various methods of investigation. Modern-day criminal investigations commonly employ many modern scientific techniques known collectively as forensic science.

Criminal investigation is an ancient science that may have roots as far back as c. 1700 BCE in the writings of the Code of Hammurabi. In the code, it is suggested that both the accuser and the accused had the right to present evidence they collected. In the modern era, criminals investigations are most often done by government police forces. Private investigators are also commonly hired to complete or assist in criminal investigations.

False evidence, fabricated evidence, forged evidence, fake evidence or tainted evidence is information created or obtained illegally in order to sway the verdict in a court case. Falsified evidence could be created by either side in a case (including the police/prosecution in a criminal case), or by someone sympathetic to either side. Misleading by suppressing evidence can also be considered a form of false evidence (by omission); however, in some cases, suppressed evidence is excluded because it cannot be proved the accused was aware of the items found or of their location. The analysis of evidence (forensic evidence) may also be forged if the person doing the forensic work finds it easier to fabricate evidence and test results than to perform the actual work involved. Parallel construction is a form of false evidence in which the evidence is truthful but its origins are untruthfully described, at times in order to avoid evidence being excluded as inadmissible due to unlawful means of procurement such as an unlawful search.

Apart from the desire for one side or another to succeed or fail in its case, the exact rationale for falsifying evidence can vary. Falsifying evidence to procure the conviction of those honestly believed guilty is considered a form of police corruption even though it is intended to (and may) result in the conviction of the guilty; however it may also reflect the incorrect prejudices of the falsifier, and it also tends to encourage corrupt police behavior generally. In the United Kingdom, this is sometimes called 'Noble Cause Corruption.' A "throw down," i.e. the planting of a weapon at a crime scene might be used by the police to justify shooting the victim in self-defense, and avoid possible prosecution for manslaughter. However, the accused might have falsified some evidence, especially if not arrested immediately, or by having other access to a crime scene and related areas.

A police dog, also known as a K-9 (phonemic abbreviation of canine), is a dog that is trained to assist police and other law enforcement officers. Their duties may include searching for drugs and explosives, locating missing people, finding crime scene evidence, protecting officers and other people, and attacking suspects who flee from officers. The breeds most commonly used by law enforcement are the German Shepherd, Belgian Malinois, Bloodhound, Dutch Shepherd, and Labrador Retriever. In recent years, the Belgian Malinois has become the leading choice for police and military work due to their intense drive, focus, agility, and smaller size, though German Shepherds remain the breed most associated with law enforcement.

Police dogs are used on a federal and local level for law enforcement purposes in many parts of the world. They are often assigned to what in somenations is referred to as a K-9 Unit, with a specific handler, and must remember several verbal cues and hand gestures. Initial training for a police dog typically takes between eight months and a year, depending on where and how they are trained, and for what purpose. Police dogs often regularly take training programs with their assigned handler to reinforce their training. In many countries, intentionally injuring or killing a police dog is a criminal offense.

A search-and-rescue (SAR) dog is a dog trained to respond to crime scenes, accidents, missing persons events, as well as natural or man-made disasters. These dogs detect human scent, which is a distinct odor of skin flakes and water and oil secretions unique to each person and have been known to find people under water, snow, and collapsed buildings, as well as remains buried underground. SAR dogs are a non-invasive aid in the location of humans, alive or deceased.

Forensic identification is the application of forensic science, or "forensics", and technology to identify specific objects from the trace evidence they leave, often at a crime scene or the scene of an accident. Forensic means "for the courts".

Forensic dentistry or forensic odontology involves the handling, examination, and evaluation of dental evidence in a criminal justice context. Forensic dentistry is used in both criminal and civil law. Forensic dentists assist investigative agencies in identifying human remains, particularly in cases when identifying information is otherwise scarce or nonexistent—for instance, identifying burn victims by consulting the victim's dental records. Forensic dentists may also be asked to assist in determining the age, race, occupation, previous dental history, and socioeconomic status of unidentified human beings.

Forensic dentists may make their determinations by using radiographs, ante- and post-mortem photographs, and DNA analysis. Another type of evidence that may be analyzed is bite marks, whether left on the victim (by the attacker), the perpetrator (from the victim of an attack), or on an object found at the crime scene. However, this latter application of forensic dentistry has proven highly controversial, as no scientific studies or evidence substantiate that bite marks can demonstrate sufficient detail for positive identification and numerous instances where experts diverge widely in their evaluations of the same bite mark evidence.