Forensic science in the context of Microscopy

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.

Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells).

Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male cone to the female cone of gymnosperms. If pollen lands on a compatible pistil or female cone, it germinates, producing a pollen tube that transfers the sperm to the ovule containing the female gametophyte. Individual pollen grains are small enough to require magnification to see detail. The study of pollen is called palynology and is highly useful in paleoecology, paleontology, archaeology, and forensics.

Chronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously established chronology. This usually requires what is commonly known as a "dating method". Several dating methods exist, depending on different criteria and techniques, and some very well known examples of disciplines using such techniques are, for example, history, geology, paleontology, archaeology, astronomy and even forensic science, since in the latter it is sometimes necessary to investigate the moment in the past during which the death of a cadaver occurred. These methods are typically identified as absolute, which involves a specified date or date range, or relative, which refers to dating which places artifacts or events on a timeline relative to other events and/or artifacts. Other markers can help place an artifact or event in a chronology, such as nearby writings and stratigraphic markers.

In forensic science, questioned document examination (QDE) is the examination of documents potentially disputed in a court of law. Its primary purpose is to provide evidence about a suspicious or questionable document using scientific processes and methods. Evidence might include alterations, the chain of possession, damage to the document, forgery, origin, authenticity, or other questions that come up when a document is challenged in court.

Sherlock Holmes (/ˈʃɜːrlɒk ˈhoʊmz/) is a fictional detective created by British author Arthur Conan Doyle. Referring to himself as a "consulting detective" in his stories, Holmes is known for his proficiency with observation, deduction, forensic science and logical reasoning that borders on the fantastic, which he employs when investigating cases for a wide variety of clients, including Scotland Yard.

The character Sherlock Holmes first appeared in print in 1887's A Study in Scarlet. His popularity became widespread with the first series of short stories in The Strand Magazine, beginning with "A Scandal in Bohemia" in 1891; additional tales appeared from then until 1927, eventually totalling four novels and 56 short stories. All but one are set in the Victorian or Edwardian eras between 1880 and 1914. Most are narrated by the character of Holmes's friend and biographer, Dr. John H. Watson, who usually accompanies Holmes during his investigations and often shares quarters with him at the address of 221B Baker Street, London, where many of the stories begin.

A crime scene is any location that may be associated with a committed crime. Crime scenes contain physical evidence that is pertinent to a criminal investigation. This evidence is collected by crime scene investigators (CSI) and law enforcement. The location of a crime scene can be the place where the crime took place or can be any area that contains evidence from the crime itself. Scenes are not only limited to a location, but can be any person, place, or object associated with the criminal behaviours that occurred.

Immediately after the discovery of a crime scene, measures must be taken to secure and protect the scene from contamination. To maintain the integrity of the scene, law enforcement must take action to block off the surrounding area as well as keep track of who comes in and goes out. By taking these precautions, officers can ensure that evidence that is collected can be used in court. Evidence that has become contaminated, tampered with, or mistreated can pollute the scene and cause a case to be thrown out of court.

Body identification is a subfield of forensic science that uses a variety of scientific and non-scientific methods to identify a body. Forensic purposes are served by rigorous scientific forensic identification techniques, but these are generally preceded by formal identification. This involves requesting a family member or friend of the victim to visually identify the body.

If a body is not badly decomposed or damaged, one or more persons who knew the deceased well can visually confirm their identity. Authorities will also compare supportive documents such as a driver's license, passport, or other authoritative photo ID before accepting a personal identification.

A fingerprint is an impression left by the friction ridges of a human finger. The recovery of partial fingerprints from a crime scene is an important method of forensic science. Moisture and grease on a finger result in fingerprints on surfaces such as glass or metal. Deliberate impressions of entire fingerprints can be obtained by ink or other substances transferred from the peaks of friction ridges on the skin to a smooth surface such as paper. Fingerprint records normally contain impressions from the pad on the last joint of fingers and thumbs, though fingerprint cards also typically record portions of lower joint areas of the fingers.

Human fingerprints are detailed, unique, difficult to alter, and durable over the life of an individual, making them suitable as long-term markers of human identity. They may be employed by police or other authorities to identify individuals who wish to conceal their identity, or to identify people who are incapacitated or dead and thus unable to identify themselves, as in the aftermath of a natural disaster.

The polymerase chain reaction (PCR) is a laboratory method widely used to amplify copies of specific DNA sequences rapidly, to enable detailed study. PCR was invented in 1983 by American biochemist Kary Mullis at Cetus Corporation. Mullis and biochemist Michael Smith, who had developed other essential ways of manipulating DNA, were jointly awarded the Nobel Prize in Chemistry in 1993.

PCR is fundamental to many of the procedures used in genetic testing, research, including analysis of ancient samples of DNA and identification of infectious agents. Using PCR, copies of very small amounts of DNA sequences are exponentially amplified in a series of cycles of temperature changes. PCR is now a common and often indispensable technique used in medical laboratory research for a broad variety of applications including biomedical research and forensic science.

A body farm is a research facility where decomposition of humans and animals can be studied in a variety of settings. The initial facility was conceived by anthropologist William M. Bass in 1981 at the University of Tennessee in Knoxville, Tennessee, where Bass was interested in studying the decomposition of a human corpse from the time of death to the time of decay. The aim was to gain a better understanding of the decomposition process, permitting the development of techniques for extracting information such as the timing and circumstances of death from human remains. Body farm research is of particular interest in forensic anthropology and related disciplines, and has applications in the fields of law enforcement and forensic science. Numerous purposes exist for these research facilities, yet their main purpose is to study and form an understanding of the decompositional changes that occur with the human body. By placing the bodies outside to face the elements, researchers are able to get a better understanding of the decomposition process. This research is then used for medical, legal and educational purposes. Following the outdoor research, skeletal remains are cleaned and curated in permanent known skeletal collections open for research. Such collections are critical for testing and developing new identification methods.

A medical classification is used to transform descriptions of medical diagnoses or procedures into standardized statistical code in a process known as clinical coding. Diagnosis classifications list diagnosis codes, which are used to track diseases and other health conditions, inclusive of chronic diseases such as diabetes mellitus and heart disease, and infectious diseases such as norovirus, the flu, and athlete's foot. Procedure classifications list procedure codes, which are used to capture interventional data. These diagnosis and procedure codes are used by health care providers, government health programs, private health insurance companies, workers' compensation carriers, software developers, and others for a variety of applications in medicine, public health and medical informatics, including:

• statistical analysis of diseases and therapeutic actions
• reimbursement (e.g., to process claims in medical billing based on diagnosis-related groups)
• knowledge-based and decision support systems
• direct surveillance of epidemic or pandemic outbreaks
• In forensic science and judiciary settings

There are country specific standards and international classification systems.

Paul Theodor Uhlenhuth (7 January 1870 in Hanover – 13 December 1957 in Freiburg im Breisgau) was a German bacteriologist and immunologist, and Professor at the University of Strasbourg (1911–1918), at the University of Marburg (1918–1923) and at the University of Freiburg (1923–1936). He was a rector of the University of Freiburg from 1928 to 1929. After his retirement in 1936, he led his own research institute in Freiburg, known as the State Research Laboratory, until his death in 1957.

He is famous in the annals of forensic science for developing the species precipitin test, known as the Uhlenhuth test, which could distinguish human blood from animal blood in 1901, a discovery which had tremendous importance in criminal justice in the 20th century. In 1915, he discovered the pathogen of Weil's disease. He also invented the arsenic treatment of syphilis and the antimony treatment of many tropical diseases, and was an influential promoter of cancer research. He was a recipient of numerous honours, and was a member of the Academy of Sciences Leopoldina and the Royal Swedish Academy of Sciences. He was nominated for the Nobel Prize in Medicine 40 times between 1910 and 1952, notably by Nobel laureate Karl Landsteiner. At the time of his death, he was one of the most celebrated medical researchers in Germany, and one of the rare examples of someone who was equally celebrated in the west and east during the Cold War.

Analytical chemistry (or chemical analysis) is the branch of chemistry concerned with the development and application of methods to identify the chemical composition of materials and quantify the amounts of components in mixtures. It focuses on methods to identify unknown compounds, possibly in a mixture or solution, and quantify a compound's presence in terms of amount of substance (in any phase), concentration (in aqueous or solution phase), percentage by mass or number of moles in a mixture of compounds (or partial pressure in the case of gas phase).

It encompasses both classical techniques (e.g. titration, gravimetric analysis) and modern instrumental approaches (e.g. spectroscopy, chromatography, mass spectrometry, electrochemical methods). Modern analytical chemistry is deeply intertwined with data analysis and chemometrics, and is increasingly shaped by trends such as automation, miniaturization, and real-time sensing, with applications across fields as diverse as biochemistry, medicinal chemistry, forensic science, archaeology, nutritional science, agricultural chemistry, chemical synthesis, metallurgy, chemical engineering and materials science.

Legal psychology is a field focused on the application of psychological principles within the legal system and its interactions with individuals. Professionals in this area are involved in understanding, assessing, evaluating potential jurors, investigating crimes and crime scenes, conducting forensic investigations The term "legal psychology" distinguishes this practical branch of psychology from the more theory-oriented field of clinical psychology.

Together, legal psychology and forensic psychology form the field more generally recognized as "psychology and law". Following earlier efforts by psychologists to address legal issues, psychology and law became a field of study in the 1960s, though that originating concern has lessened over time. The multidisciplinary American Psychological Association's Division 41, the American Psychology–Law Society, is active with the goal of promoting the contributions of psychology to the understanding of law and legal systems through research; as well as providing education to psychologists in legal issues and providing education to legal personnel on psychological issues. Further, its mandate is to inform the psychological and legal communities, along with the general public, about current research, education, and services in the field of psychology and law. There are similar societies in Canada, Britain, and Europe.

X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. When a material is illuminated with high-energy X-rays, its atoms can become excited and emit their own unique, characteristic X-rays—a process similar to how a blacklight makes certain colors fluoresce. By measuring the energy and intensity of these emitted "secondary" X-rays, scientists can identify which elements are present in the sample and in what quantities. Thus, XRF is the basis of a non-destructive analytical technique widely used for elemental analysis and chemical analysis, particularly in the investigation of metals, glass, ceramics and building materials, and for research in geochemistry, forensic science, archaeology and art objects such as paintings.

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".