A criminalist (aka crime scene technician, examiner, or investigator) is a person who searches for, collects, and preserves physical evidence in the investigation of crime and suspected criminals [see job description]. They typically work in city or regional crime labs and are expected to do more than the forensic scientists and crime lab technicians there.
They are expected to be on call 24 hours a day to go out to crime scenes, frankly when and where detectives are stumped. Some jurisdictions require the presence of a criminalist at all major crime scenes. The services of a criminalist are used at the beginning of a case. By contrast, the services of a forensic scientist are primarily used at the end, or courtroom testimony phase, of a case. All crime lab employees must be ready to offer expert testimony in court, however.
Criminalists usually get called to testify about matters of contamination, cross-contamination, and chain of custody, but many of them (senior criminalists) have developed an interpretive expertise, for example, in blood spatter analysis, trace evidence, impression evidence, or drug identification, as well as skills at crime reconstruction and sometimes profiling (Levinson & Almog 1989).
The term criminalistics (Kriminalistik) was first used by Hans Gross in 1891
But the term was mostly forgotten until the 1960s when a series of cooperative movements took place between police agencies and criminal justice or criminology departments to establish criminalistics (Univ. of California) and forensic science (Michigan State) college programs. Professors Paul Kirk in California and Ralph Turner in Michigan (among many others) were pioneers in those movements.
As Osterburg and Ward (2000) imply, criminalistics programs (available at forty-one community colleges and only one four-year college) followed the police science model to record, identify, and interpret the minutia (minute details) of physical evidence, and forensic science (available at fourteen four-year colleges and nine master’s degree programs) followed the medical science model to apply generally accepted principles of established disciplines (like pathology, serology, toxicology, odontology, and psychiatry) to the scientific examination of physical evidence.
Forensic science is the broader term because criminalistics is a branch of forensic science. «Forensic» is simply an adjective that can be put in front of any science applied to answering legal questions. The American Academy of Forensic Sciences web site highlights about twenty various degree programs that relate to some aspect of criminalistics or forensic science education. The world’s first crime laboratory was established by Edmond Locard in Lyon, France during 1910.
The famous Locard Exchange Principle that «every contact leaves a trace» is named for him, after Locard solved a strangling case by using fingernail scrapings. In America, a few major cities and the FBI obtained crime labs during the 1930s, and by the mid-1970’s (the birth of criminal justice), 47 states had crime labs. A few criminal justice programs that existed prior to the explosion of the field in 1974 offered a criminalistics or forensic science concentration, but today, most criminal justice programs only have one course in criminal investigation.
Post-1975, the criminal justice model became an attempt to make sense of whole systems of justice, and the criminology model, dominated heavily by sociology until about 1990, became theory, research, and policy-driven. Many criminalists consider themselves (professional) criminologists, but few criminologists consider themselves criminalists.
With federal police agencies, two organizations stand out above the rest, the FBI and ATF, mainly because their crime labs are pretty much considered the tops in the field and a model for elsewhere.
FBI crime lab has 4 sections: Scientific analysis (DNA, Firearms-toolmarks, Hairs and Fibers, Materials Analysis, Chemistry and Toxicology, Questioned Documents; Special Projects (film, photography, composites, art, computer design); Fingerprinting (some 200 million records); Investigative Operations and Support (grew out of Questioned Documents unit and includes lie detection of various sorts). The FBI lab only handles violent crime, works exclusively for the prosecution, and is considered the world’s largest lab.
ATF crime lab handles Explosives, bombs, arsons (and does it well); Trace evidence and deciphering firearms ownership and usage; Disaster response teams (kind of like FEMA); Field support; and some Gang intelligence record keeping. ATF labs are typically very high-tech and have always been accredited.
It’s typical for a Crime Lab to have 4 divisions under a Director’s Office: a section dealing with anything pertaining to fluids, this being called a Serology Division; a section dealing with unknown substances, drugs, or poisons, this being called a Chemistry or Toxicology Division; a section dealing with anything so small, like hairs or fibers, that they need to be looked at under a microscope, this being called a Trace Evidence, Biology, or Microscopy Division; and a section dealing with guns, weapons, instrumentation, or whatever, this being called a Ballistics, Firearms, or Fingerprinting (Dusting and Lifting) Division (where Interns usually work). There are about 350 crime laboratories in the U.S. and at least 80% of them are affiliated with a police agency (where they typically hold bureau status in the organization). The rest are located in the private sector and some of these are exemplary and known for a particular specialty: Cellmark Diagnostics (for DNA), Battelle Corp. (for arson cases), and Sirchie Corp. (for fingerprinting and trace evidence collection), to name a few. There is a shortage of DNA laboratories since only 120 labs are set up to do DNA testing (Steadman 2002). Almost all labs in existence are forensic labs, where «forensic» means the experts there are available to give courtroom opinions, but when a lab is set up to receive evidence from ongoing criminal investigations, this is called casework, and the lab is referred to as a casework lab.
Before any laboratory work is done, it must be ensured that the workplace is clean and contamination free. Then, the evidence is visually inspected and properly described to document its condition. Often, it will be photographed, weighed, and sketched. Then, the laboratory worker (criminalist, crime lab technician, or forensic scientist) will have to figure out what tests are appropriate, if sufficient amounts of the evidence exist, properly dissect the portion to be tested, and properly prepare the testing material (which might include the delicate mixing of numerous chemical compounds), all the while continuing to document each step.
Only then does any testing begin. Some tests include as many as five or six separate procedures, each of which must be properly performed and documented, the evidence properly repackaged and relabeled, and once again transported to storage. Only then does the lab worker engage in the process of interpreting what the experiments have disclosed.
A report is prepared and the contents of that report must be precisely correct. At the prosecutor’s discretion, the evidence has to make it back to the police evidence room, where it will be stored until he/she decides they want to use it or want more testing performed, in which case it goes back to the crime lab. It should be fairly evident that all this transportation of evidence gives rise to numerous possibilities for error in the form of destruction, mishandling, and contamination.
Generally, whenever a lab applies for accreditation, it has to meet certain minimum requirements which include, among other things, the development and publication of:
- 1) a Quality Control Manual,
- 2) a Quality Assurance Manual,
- 3) a Lab Testing Protocol, and
- 4) a program for proficiency testing. Quality control refers to measures that are taken to ensure that the product, for example a DNA-typing result and its interpretation, meets a specified standard of quality.
Quality assurance refers to measures that are taken by a laboratory to monitor, verify, and document its performance. A basic business principle is that QA serves as a check on QC. Protocols consist of a few hundred pages of highly technical manuals and should include such things as «validation studies» which the lab performed itself to make it capable of performing tests in any particular discipline. Proficiency testing determines if the lab workers individually, and the laboratories as institutions, are performing up to the standards of the profession.
In these tests, samples to be examined are given to a laboratory or particular worker, but the results are already known by a test giver. There are two methods employed in administering these tests, blind and known. In the blind test, the lab worker doesn’t know that a test is taking place; they think the evidence sample they are working on is just another case. The open proficiency test is like an open book exam. In addition, individual lab workers join associations to beef up their resumes. The two main ones are the American Academy of Forensic Sciences (AAFS), the American Board of Criminalistics (ABC).
Physical evidence is part of the «holy trinity» for solving crimes — physical evidence, witnesses, and confessions. Without one of the first two, there is little chance of even finding a suspect. In homicide and sexual assault cases, physical evidence is the number one determinant of guilt or innocence.
Physical evidence is also the number one provider of extraordinary clearances, where police can link different offenses at different times and places with the same offender. Working with physical evidence means being aware at all times of what the prosecutor needs to win the case in court. This means knowing the Types of Evidence and the Laws of Evidence.
Without doubt, the most important concept in criminalistics is identification, or what Paul Kirk called individualization (Kirk 1936). Identification produces unequivocal (certain) interpretation. An equivocal crime scene, by comparison, yields physical evidence subject to different interpretation (and is the basis for crime reconstruction and profiling).
When a number of details are put together (as in points of comparison), so that they constitute a class of one (by itself), they are said to establish an identity, also called individual characteristics, or entities in a class by itself. At this point, if there are similarities between evidence from the crime scene and evidence from a suspect, the expert can say, without a doubt, that identity has been individualized.
It is important to clearly understand the concepts of identity, match, class and individual characteristics. Identity is a set of characteristics (combinations of class characteristics or combinations of class and individual characteristics) by which a thing is recognizable or known. Identity is the same as pattern. A pattern is established, for example, when a particular piece of class evidence like fiber (for which there are large quantities in the population) is put together with another piece of class evidence like red hair (which usually only exists in the subpopulation of white people).
It cannot be said the investigator has «individualized» anything at this point, but the red hair in this example can be considered enough of an individual characteristic which combines with the class characteristic to establish identity. At this point, if there is a «match» between the fibers and hair from the crime scene with a suspect, the examiner can say the crime scene (unknown or questioned) sample «may have come from the same source» as the suspect’s (known or exemplar) sample, which is sufficient for probable cause.
Identity can also be used to conclusively eliminate people as suspects. Class characteristics alone do not allow matches with a single suspect. Matches for evidence with individual characteristics do allow pinpointing a particular suspect. Matches at the individual level are called similarities, because in theory, there’s no such thing as a perfect match. An example of a similarity, or match in individual characteristics, would be a number of comparable points of comparison between the friction ridge lines on a latent (crime scene) fingerprint with the fingerprints of a particular suspect.
This kind of (true) match allows the examiner to say that, because the similarities outweigh any dissimilarities, the crime scene (unknown or questioned) sample «did come from the same source» as the suspect’s (known or exemplar) sample, which is sufficient, most of time, for proof beyond a reasonable doubt. Reliability and integrity are enhanced if the examiner has conducted tests on standards using controls. A standard is the opposite of exemplar.
An exemplar always comes from a suspect or something representing a known modus operandi or signature. Standards consist of simultaneous tests done on items taken from the «background» or nearby the crime scene (control sample), items similar to one the suspect used, such as test firings of a similar weapon (standard sample), or items used for calibration purposes kept in stock at the lab (reference sample). The astute student may notice that the word «match» is used a couple of different ways in criminalistics.
Nobody uses the phrase (true) match, for example, like I have used in my explanations above. Some people prefer the term «matching» (Ramsland 2001). Abuse of the term «match» is even worse in forensic science, which allows different disciplines to set their own criteria and standards. To wrap things up, let’s conclude with an interesting topic — the points of comparison method — and then attempt to present a table which classifies evidence by their class and individual characteristics.