Crime laboratories

DEFINITION: Public and private facilities at which forensic specialists analyze materials collected from crime scenes for purposes of identification and interpretation.

SIGNIFICANCE: Since the founding of the first crime laboratory in France in 1910, these facilities have employed a scientific approach to dealing with evidence collected by crime scene investigators. The work conducted by crime laboratories provides invaluable assistance to criminal investigators and legal professionals around the world.

Forensic scientists, also known as criminalists, apply scientific methods to the analysis, identification, and interpretation of evidence gathered at crime scenes. They conduct much of their work at crime laboratories, facilities that are specially equipped with the technological and other tools they need to carry out the careful examination of evidence.

Sherlock Holmes and Early Crime Laboratories

A direct connection can be drawn between the popularization of Sir Arthur Conan Doyle’s detective novels and the establishment of the first crime laboratory. Renowned for creating the fictional detective Sherlock Holmes, Doyle was well-trained in science. He was a practicing physician with a strongly held conviction that the scientific method can be applied logically and effectively to solving crimes. In 1887, Doyle introduced the world to Sherlock Holmes and his sidekick, Dr. Watson. He continued to write about them for roughly forty years.

Among Doyle’s most ardent fans was Edmond Locard, a Frenchman who devoured the Sherlock Holmes stories. Convinced of the efficacy of applying the scientific method to solving crimes, Locard established the first police forensic crime laboratory, the Institute of Criminalistics for the Rhône Police in Lyon, France. This early laboratory occupied modest quarters in the Lyon courthouse. Locard, whose laboratory equipment consisted of a microscope and other basic equipment, gained credibility by using scientific means to solve a puzzle surrounding the counterfeiting of coins in the Lyon area. Obtaining some clothes belonging to a suspect, he extracted from them samples of dirt in which he found traces of metal that matched the metal in the counterfeit coins. This discovery caused the suspect to confess and gave people confidence in Locard’s methods.

The first crime laboratory in the United States was established in Los Angeles by August Vollmer in 1923. It was not until 1932 that the Federal Bureau of Investigation (FBI), under the leadership of J. Edgar Hoover, established its first crime laboratory. From modest beginnings, equipped with only a microscope and minimal equipment, such as ultraviolet lamps, the FBI Laboratory grew to become one of the most extensive and sophisticated crime laboratory in the world.

Discovering and Preserving Evidence

One of the most important elements in gathering evidence from the scene of a crime or accident is the preservation of that evidence so that it is not contaminated following its discovery. For each piece of evidence, a record (referred to as the chain of custody) is kept of every single person who deals with the evidence from the time it is discovered to the day the evidence is used in court or in some other official venue.

Evidence must be gathered by people trained in forensic evidence-collection techniques. Before evidence samples are collected for transportation to a crime laboratory, investigators examine the evidence as they find it at the crime or accident scene, which the police preserve as nearly as they can, making it inaccessible to unauthorized or untrained people. In the early stages of an investigation, the scene is photographed from a variety of angles, careful measurements are taken, and the scene is sketched by investigators (forensic artists are called in when a more visual rendering of the crime scene or specific individuals is required).

Among the kinds of evidence that criminalists gather are fingerprints. Surfaces that may hold prints are carefully dusted with a powder that creates strong contrasts in the ridges and valleys of such prints. Fingerprints that are uncovered in this way are first photographed and then lifted from the surface with adhesive tape and transferred to a fingerprint card. Visible prints, such as those found on surfaces in blood or grease, are photographed and may be transferred to fingerprint cards.

Criminalists also collect tire-track and footprint evidence, measuring and photographing such impressions and often making plaster casts of them to preserve them for analysis. Trace evidence—substances such as hairs, fibers, and fragments of glass or paint—is collected with vacuum cleaners specially designed for this purpose. Items such as knives, shell casings, and instruments that may have been used as weapons are carefully collected so that any fingerprints or traces of blood, hair, or flesh on them are preserved. Each piece of evidence collected is properly packaged and carefully labeled before it is transported to the laboratory for analysis.

Laboratory Equipment and Techniques

Crime laboratories are equipped with a variety of specialized microscopes that are used to closely examine the materials found at crime scenes. Stereoscopic binocular microscopes are essential for the examination of trace evidence detected at the scenes of crimes and may also be used to examine and classify handwriting and text created by typewriters and computer printers.

Polarizing microscopes enable forensic scientists to examine and identify minerals, narcotics, and other elements by enlarging their crystal forms. Essential to those engaged in ballistic examinations, comparison microscopes enable forensic scientists to compare the markings on shells and casings found at crime scenes with other samples, possibly linking them to particular weapons.

Using spectrophotometry, investigators can uncover wavelengths of light that the human eye cannot see. The spectrophotometer shows the patterns of such rays, and by examining these patterns, criminalists can detect alterations on documents, such as erasures, that may indicate fraud or forgery. The gas chromatograph, a sophisticated instrument that identifies the constituent components of substances and measures each component, is used in the analysis of many different unknown substances. It is also the instrument that forensic scientists employ to determine the blood alcohol levels of persons suspected of driving under the influence.

The analysis of DNA (deoxyribonucleic acid) evidence has become an increasingly important part of the work of crime laboratories. By comparing DNA profiles derived from the DNA extracted from biological materials—such as blood, semen, saliva, and hair—found at crime scenes with the DNA profiles of known persons, forensic scientists can identify victims, link suspects to crimes, and exclude innocent persons from suspicion.

Training of Crime Lab Personnel

Nearly all law enforcement officers receive some training in identifying and handling the evidence with which they come into contact at crime scenes. Because of the growing level of sophistication of the work done in crime laboratories, many colleges and universities in the United States have established special programs designed to train forensic scientists.

Generally, one requirement for employment in a crime laboratory in the United States is an undergraduate degree in chemistry, a related scientific field, or in some aspect of criminology. The undergraduate preparation of forensic scientists usually includes extensive coursework in a variety of chemistry subdisciplines as well as courses in anatomy, physics, biology, geology, and psychology.

Some major American universities offer training in forensic science that leads to a master of Science degree; some offer doctorates in criminalistics or forensic science. Many institutions of higher learning provide short training courses in forensic science for law enforcement personnel and for practicing attorneys; these are helpful for persons within the criminal justice system who lack the typical undergraduate background in forensics or who seek to update their training.

Most forensic scientists in the United States work for local, state, or federal public agencies, although some are private consultants for businesses, industry groups, or other private organizations. The American Academy of Forensic Sciences encourages training and research in the field. Its bimonthly publication, the Journal of Forensic Sciences, informs readers about current research in all branches of the forensic sciences. The American Society of Crime Laboratory Directors (ASCLD), a professional society open to past and current laboratory directors and forensic science educators, was established in 1974 to grant accreditation (through the LAB [Laboratory Accreditation Board]) to crime laboratories that voluntarily invited examiners to evaluate their programs. The ASCLD merged into the American National Standards Institute (ANSI) National Accreditation Board (ANAB) in 2016.

In 2020, the United States had 326 standalone forensic labs and multilab systems. These labs received 3.3 million requests for service, of which 33 percent were controlled substances analysis requests. At the end of 2020, the labs had a combined backlog of more than 710,000 requests that had not been completed within thirty days of submission.

Bibliography

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