EXPERT EVIDENCE AND
AREAS OF EXPERT WITNESS TESTIMONY

The scope of expert testimony is infinite and includes any relevant subject, so long as there are "experts" willing to venture an opinion distinctly related to a generally accepted science, profession, business, or occupation beyond the experience of the layman. Courts have broad discretion in whom they will accept as an expert witness. Anybody can become an "expert" if they can establish, to the satisfaction of a judge, that they possess some particular experience, training, education, or combination thereof that will aid the court in arriving at the truth on some particular matter. However, depending upon the subject matter or expertise, there are specific rules and procedures for establishing the foundation, competency, and weight of the expert testimony. For the most part, juries are mostly allowed to accept or ignore the expert's testimony, but not always.

In providing their impartial, objective services, experts only offer a sense of reasonable scientific certainty, not absolute certainty. When two experts of unquestionable integrity disagree, it's the one who appears more impartial and objective that is given more credence by the court. In other cases, it's more appropriate to compel or make use of a court-appointed expert witness. Such compelled experts, under subpoena duces tecum (bring all documents), must usually be paid a fee, as well as another type of expert, called a meta-expert, who under amicus curiae (friend of the court), files a brief trying to resolve complex scientific issues or responds at a distance to hypothetical questions. Yet another type of expert, the expert-advisor (not really a witness), assists one side of the case in jury selection and cross-examination strategies. 

Experts are expected to be advocates of the truth, equal advocates of the prosecution or defense. However, defense experts are usually paid a fee or have their expenses picked up. They work on a free-lance, case-by-case basis. Prosecution experts are usually employees of the state, and if "forensic science" is somewhere in their job description, they are expected to always be "on call" to testify without any extra compensation (with few exceptions). Although the prosecution has the advantage of a ready-made pool of experts, the risks are greater since if any government employee expert is discredited or impeached since the taint goes all the way back to the lab, agency, or department they represent. OK, to recap the different TYPES of experts:

ALCOHOL INTOXICATION - Some courts allow police officers, specially trained in a National Safety Council approved course, to testify as to impairment on the standards of .05 (judgment), .08 (coordination), and .10 (reflexes), based on breathalyzer-type instruments, various field sobriety tests, and Horizontal Gaze Nystagmus which measures the inability of the eyes (involuntary jerking) to maintain visual fixation as they are turned to the side. 

AUTOMOBILE AND AIRPLANE CRASHES - Some courts allow patrolmen with extensive experience in accident investigation and refresher course qualification to testify as to speed, point of impact, and other non-ultimate issues. Airplane expertise usually requires an engineering degree and experience. It is common for this kind of expert to demonstrate exhibits showing reconstruction of the accident.

BALLISTICS - The science of forensic ballistics is well-established but frequently challenged. Most courts will allow testimony showing that the bullet which killed a person was fired from a weapon belonging to a defendant. Likewise, testimony as to breechface and/or firing-pin markings, striation patterns, and gunpowder residue is commonly accepted. Glass and wound pattern analysis has yet to gain widespread acceptance. Courtroom demonstrations are usually prohibited, so laboratory results are often substituted, with this opening the door to whether the lab is comparable to the FBI's lab or another major laboratory. There are a variety of different ballistic techniques, but they all usually have to do with science of motion for projectiles.

BITE MARK ANALYSIS - Normally would require credentials in forensic dentistry, and special training in the ABFO (American Board of Forensic Odontology) scale and other pathologist skills, such as saliva extraction. This field took a hit about a decade ago when an association discredited a famous expert for his special blue lighting technique and interpretation methods. A highly controversial field, even for forensic dentists.

BLOOD GROUPING TESTS AND BLOOD SPATTER ANALYSIS - Some courts are allowing competent analysts (other than serologists) to admit results of field tests on blood samples, especially when it comes to determining secretors. Normally, a serologist can admit more refined tests without much challenge. Spatter (which should be spelled splatter) analysis is part of the detective craft. Based on the laws of physics, the tail of a blood drop always points to the origin, the size estimates height, and shape determines angle of impact. When admitted, usually accompanied by an exhibit explaining the principles. Courts have wide latitude in this area.

DNA (Deoxyribonucleic Acid) TESTS - There have been significant breakthroughs, but it is also one of the most fiercely challenged areas. DNA "fingerprinting" is generally considered reliable, but challenges continue to occur at the laboratory protocol (contamination) level and the extent of interpretation (how much is left to the jury).

DOCUMENT EXAMINATION - A growing area of fraud and white-collar crime investigation. With white-collar crime, requires almost the equivalent of a degree in accounting but is readily attainable thru certification programs. Questioned document examination ascertains the authenticity or source of handwriting or typewriting. Graphology is handwriting analysis. Other experts are involved in the analysis of paper and ink, obliterations, and erasures. Some insurance fraud and arson investigators have a specialty with burned or charred documents.

DRUG COURIER PROFILING AND PROFILING IN GENERAL - Some courts are allowing specially trained police officers (especially DEA agents) an expertise in identifying movements of a drug dealer (or other criminal), the meaning of "drug (or gang) lingo", paraphernalia, the significance of phone traffic and other behaviors. John (solicitation of prostitution) profiling has also received court approval. Serial killer profiling is a highly controversial area in search of a scientific method. So-called racial profiling is about traffic stops, and has little to do with science at all. 

EYEWITNESS IDENTIFICATION - Usually a social psychologist who augments or impeaches the witness' cognitive or perceptual abilities at a showup, lineup, or recollection of facts. Memory experts tend to bring a lot of books to the courtroom, and Perception experts tend to host simple courtroom demonstrations. Both tend to talk the language of misperception: assimilation/contrast effects, sociodemographic bias, lighting, figure/ground gestalt, etc.

FINGERPRINT IDENTIFICATION - Very well-established area where an average officer testifies they obtained a set of latent prints from the crime scene, but to connect them with a known suspect usually requires an AFIS-certified expert. Usually such experts are available or in training at state or regional crime labs and police departments. Under some circumstances, the courts will allow average officers to testify. Usually, enlarged photographs or other exhibits demonstrate the points of comparison upon which the conclusion was reached. In a crime lab, the fingerprint unit is called the Latent Fingerprint Unit and processes latent prints that come in from police departments.

FIREARMS IDENTIFICATION - This can refer to the work of a crime lab unit or a free-lance gun expert who is capable of examining cartridge cases, shells, and ammunition of all types. Garments and other objects are also sometimes examined in terms of discharge residue. Firearms identifiers rely upon some of the same principles as tool mark experts.

FORENSIC ANTHROPOLOGY - An area involved in such things as time of death, age, race, and sex of victim, and reconstruction of facial appearance from skeletal remains. The area might also involve counting the size of the largest maggot to give an estimate of the time of death. Often, a high-tech field using computer reconstruction of the skin around skeletal remains or age-progression on missing persons. Another related specialty area involves helping identify victims of mass disasters, like plane crashes.

FORENSIC BIOLOGY - This most commonly describes biologists and serologists who work in a crime lab who identify and type dried bloodstains, other body fluids, and DNA. Others work with hairs and fibers as well as identify and compare botanical specimens such as wood and plants.

FORENSIC ENGINEERING - A broad field most often involving the study of accident scenes, structural failure analysis, and sometimes explosions or fires. The expertise quite usually consists of opinion on the ultimate issue, that is, which party was responsible and/or negligent.

FORENSIC ENTOMOLOGY - The study of insects and their relation to a criminal investigation, such as the analysis of larvae and maggots, but also sometimes involving a particular knowledge of insects, their habitats, life cycles, and habits.

FORENSIC ODONTOLOGY - Also called forensic dentistry, this is the study of the hardest substance in the human body, teeth enamel. With the use of dental records, X-rays, casts, or even a photograph of a person's smile, experts can often make identifications and comparisons. A related subspecialty is bite mark analysis. 

FORENSIC PATHOLOGY - A title for some extra-qualified county coroners or medical examiners who work closely with police but "own" the body at the crime scene. Numerous techniques used here, depending upon financial resources of a community, but still based around the autopsy. The expertise involves the medico-legal investigation of sudden, unnatural, unexplained, or violent deaths.

FORENSIC PHYSICAL SCIENCE - This most commonly describes the services provided by a physical science unit of a crime laboratory where the techniques of chemistry, physics, and geology are brought to bear on the identification of crime scene evidence. Such personnel are usually called criminalists and perform a variety of tests as well as use analytical instruments on trace evidence such as soil, paint, and glass.

FORENSIC PSYCHIATRY - A broad term for a diverse field that covers everything from evaluations of competency to stand trial, insanity, and particular relationships between certain psychological conditions and human behaviors.

HAIR AND FIBER ANALYSIS - Generally relies upon laboratory devices involving the techniques of Spectrography (absorption of light by a substance) and Chromotography (the chemical reactions of a substance) to produce findings such as what you had to eat three years ago (in hair samples). Fiber analysis tends to use the simple means of 10x microscopes (or higher).

HANDWRITING COMPARISON - Usually requires some special training and experience in handwriting analysis, and in addition, a familiarity with the handwriting of the individual in question. Most courts allow the expert "a high level of belief" rather than absolute certainty, and a sample size of 10 points of comparison is becoming standard.

HYPNOSIS - Generally not acceptable in most courts of law, and frequently challenged even if used for victim memory refreshment where it is allowed. An interesting field based on some of the same principles as interrogation in police work.

MICROTRACE ANALYSIS - The phrase used to describe a variety of techniques all involving study of a specimen under a microscope. Evidence is collected using a micro-vacuum like the kind that clean computer keyboard keys. The expertise is called forensic physical science, general forensic science, evidence collection, or criminalistics. 

NEUTRON ACTIVATION ANALYSIS - Some courts are allowing this, which is a fancy name for swabbing a nitric acid solution over the webbed portion of a person's hand to see if the residual levels of antimony and barium are typical of a person who has recently fired a gun. Holds the promise of detecting other things over a longer time period.

PHOTOGRAPHY - Police photography is fast becoming an expert area, now with infrared and other high-tech devices. Part of the detective craft has always been to tell a story about the crime using pictures, and crime scene photography has always had its own standards over and above what the court requires. Digital photography needs to have similar standards because photographs can be easily retouched by computers. Amateur photography experts (who know their filters and lenses) are sometimes used by the courts in some specialized matters, and photography laboratories often make use of specialized techniques, such as infrared, ultraviolet, and X-ray. If a photography unit exists in a crime lab, this unit usually helps prepare courtroom exhibits.

PHYSICAL AND MENTAL CONDITION - Experts in this area are usually medical doctors or psychiatrists, but it is not usually necessary to be a licensed medical practitioner. Researchers, optometrists, toxicologists, or even medical technicians have been allowed to testify with the exception that psychiatric testimony must be given by a psychiatrist, not a psychologist. Even clinical psychologists are prohibited from testifying in most jurisdictions. Courts have wide latitude in deciding whether testimony going to the defendant's mental state (such as the ability to form intent) is admissible.

POLYGRAPH EXAMINATION - Generally not acceptable in most courts of law because of unreliability and a lack of recognized training programs. However, may be admitted if both parties (defense and prosecution) consent, but any arrangements (or results) are non-binding for the defense. An alternative to the polygraph, called the Psychological Stress Evaluator, has come out in recent years, but it also has yet to gain acceptance. The polygraph is better thought of as a tool for the investigator and not the forensic scientist.

SKETCH ARTIST - The area of forensic art has remained in a state of infancy, but has included such craft techniques as suspect composites and crime scene sketching. The trend is to use computer software, mapping programs, and high-tech projection devices for courtroom use.

SOIL SAMPLE ANALYSIS - Usually requires education and experience with agricultural science, geology, and/or chemistry. Techniques such as the density gradience test (comparing two samples to within 50 feet of one another) are easily doable in any laboratory. More refined tests to exact a location unlike anywhere else on earch requires a more sophisticated laboratory.

SPEED DETECTION READINGS - RADAR (Radio Detection and Ranging) devices have long been acceptable to the courts because they are based on the well-established Doppler effect, and police departments have adequately demonstrated sufficient training and fine-tuning in their use. However, some courts have thrown out radar evidence when the police had no record of calibration tests on the LED circuitry and/or the tuning forks used in calibration. In addition, occasional defense attorney research turns up such things as cosine, batching, and shadowing errors which inherently plague the use of these devices. VASCAR (Visual Average Speed Computer and Recorder) is a more mechanical error-free device involving the throwing of switches as a car passes between two fixed points, with the officer assisted in the dt = r x t formula. More recently, LASER guns have come into widespread usage, which can also pickup sounds behind panes of glass, but no known court case has judged on them yet.

TOOL MARK ANALYSIS - A detective craft involving casting impressions (marks left behind on a softer surface) and lifting imprints (marks left behind on hard surfaces). Also involves some specialized knowledge in the manufacture and use of hammers, pry bars, etc. Usually the cast or imprint is admitted into physical evidence with the witness testifying as to chain of custody rather than as an expert. Tool mark analysts rely upon some of the same principles as firearms identification experts.

TOXICOLOGY - Some courts allow expertise at the level of lab technician to qualify, but generally this area requires a degree in Chemistry or Medicine, often at the master's level. Involves tests for poisons, narcotics, blood, or other bodily fluids. Often, a toxicology unit also has responsibility for drug and alcohol identification as well as training others in alcohol intoxication testing.

TRUTH SERUM RESULTS - Also called Narcoanalysis, it is important to remember than confessions extracted under the administration of drugs is constitutionally inadmissible. Some courts, however, have admitted interpretations of statements if not the tests themselves by expert medical psychiatric witnesses. These situations usually involve a placebo (sodium amytal or sodium pentothal - which have no "truth telling" properties but cause someone to speak more freely; as opposed to scopolamine - which does have a "truth telling" chemical effect).

TYPEWRITER COMPARISON - Long acceptable, the techniques of showing that a certain document came from a certain typewriter have required little by way of qualification, although the FBI has a laboratory for this. In some cases, an expert can tell if a certain person typed the document based upon personal style characteristics in manner of punctuation, length of lines, depth of indentation, etc. More recently, computer and computer printer expertise is a new development.

VOICE PRINT ANALYSIS - Spectrographic voice analysis has not gained the degree of general acceptance to make it admissible in most courts mostly due to limited number of experts. In most cases, the jury is allowed to hear the samples themselves. It is most often used in cases involving telephoned threats or tape-recorded messages by investigators and not forensic scientists. 

INTERNET RESOURCES:
I. Claims.com
II. ExpertPages.com
III. Ewitness.com