Forensic Dentistry

Updated: Jul 29, 2014
  • Author: Stuart A Caplan, DDS, MS; Chief Editor: J Scott Denton, MD  more...
  • Print
Overview

Overview

"Forensic dentistry is the study and practice of aspects of dentistry that are relevant to legal problems." (Encyclopaedia Britannica, 2009) [1]

The words intriguing, mysterious, and fascinating describe the study of ancient remains. Museums abound with archaeologic and anthropologic exhibits that include teeth and jaws (see the following images).

The Ford specimen of retentive prosthesis. This im The Ford specimen of retentive prosthesis. This image depicts the anterior teeth of the lower jaw of a male skeleton from an open sarcophagus, Sidon, 5th century BCE.
The earliest known human fossil, 1.8 million years The earliest known human fossil, 1.8 million years ago, is identified as a Homo erectus mandible from Dimanisi in the Republic of Georgia.

Dental artifacts can shed a wealth of information pertaining to our long dead ancestors and vanished civilizations. Researchers have examined the remains of Homo erectus from Kenya, where growth rates of the dentition were almost twice those of modern man. [2] Studies of isolated hunter-gatherer populations show extreme tooth-wear patterns and chipping (see the images below). Interproximal grooving of Hopewellian Indians from Kansas (ca 200-1000 CE) were specific to that group, as there was no evidence of this practice in other skeletal groups of the 2 regional pre-Colombian populations. [3]

This prehistoric sample differs from the effects o This prehistoric sample differs from the effects of diets of agricultural populations by the relative lack of caries, periodontal disease, wear, and antemortem tooth loss. The arrows point to occlusal chipping in cast from an adult Batak male, age 28 years. (Turner CG, II, Eder JF. Dental pathology, wear, and diet in a hunting and gathering forest-dwelling group: the Batak people of Palawan Island, the Philippines. In: Harris EF, ed. Dental Anthropology: A Publication of the Dental Anthropology Association. Memphis, Tenn: University of Tennessee; 2006:19(1).)
Periodontal disease in cast from an adult Batak fe Periodontal disease in cast from an adult Batak female, age 23 years. (Turner CG, II, Eder JF. Dental pathology, wear, and diet in a hunting and gathering forest-dwelling group: the Batak people of Palawan Island, the Philippines. In: Harris EF, ed. Dental Anthropology: A Publication of the Dental Anthropology Association. Memphis, Tenn: University of Tennessee; 2006:19(1).)

Although an Egyptian mandible from 3000-2500 BCE shows evidence of oral surgery, it was not until the 7th century BCE that the Etruscans began to fashion replacements for missing teeth. Dental restorations and tooth replacements were later employed by many geographically diverse, developing civilizations, as can be seen in the following images.

A piece of iron placed in the socket of a soldier A piece of iron placed in the socket of a soldier with a missing molar.
Mayans carved shells to fit in empty sockets. Mayans carved shells to fit in empty sockets.
Ivory teeth carved to fit in sockets or splinted t Ivory teeth carved to fit in sockets or splinted together were common among the wealthier segments of early civilizations.

When the Roman Empire expanded to include the Etruscans, their influence in casting gold was acquired. The "lost wax technique" (only recently replaced with optical and laser scans) was a process by which a carved wax pattern of a crown was invested in an iron ring with a gypsum material. After burning out the wax by heating in an oven, molten gold was cast into the ring using centrifugal force. The accuracy of this process emphasized the importance placed on replacing missing or fractured teeth with crowns or fixed bridgework. Note also the Crimes-Table VII, Law X, in the Twelve Tables of Rome:

"When anyone knocks a tooth out of the gum of a freeman, he shall be fined three hundred asses; if he knocks one out of the gum of a slave, he shall be fined one hundred-fifty asses."

Identification through dentition may have begun in 49 BCE with Agrippa, Emperor Nero's mother, who had Lollia Paulina, the mistress of her husband Claudius, killed and her head brought to her for identification by a discolored tooth. Similarly, Nero's mistress had him kill his first wife, who was identified by a canine.

In the Middle Ages, with the exception of a progressive-thinking Spanish Moor in the 10th century, forensic dentistry and dentistry in general abandoned the early techniques in favor of barber-surgeons. Teeth recovered from the Dark Ages have, nonetheless, provided some useful forensic evidence. When modern scientists suspected Yersinia pestis as the cause of the bubonic plague, they were able to confirm their theory by extracting bacterial DNA from some dental pulps.

Over the next 1000 years, little happened in dental forensics. Then, in 1776 at the Battle of Bunker Hill, Paul Revere identified General Joseph Warren by his having previously adjusted the general's dental prosthesis. The next major advances were heralded by the emergence of a novel medical technique at the end of the 19th century-radiology.

See also the following:

Next:

Radiology and Forensic Odontology

In 1895, the first radiology machines allowed for more sophisticated forensic evaluation. Internal details of the maxilla and mandible became useful to the dental investigator during examination of the skull. Anatomic landmarks, bone loss, caries, crowns, fixed bridges, and tooth restorations show radiolucencies or radio-opacities in antemortem radiographs, which may later be matched to those on postmortem films (see the following images). However, investigators may be challenged in cases in which there is an inconsistency of radiologic orientation between antemortem and postmortem radiographs. [4]

Antemortem image of frontal sinuses. Antemortem image of frontal sinuses.
Postmortem view of the frontal sinuses in the prev Postmortem view of the frontal sinuses in the previous image. Dehydration may have accounted for the relative clarity of the film as compared with the antemortem film in the previous image.
This radiograph of the maxillary sinus shows anoth This radiograph of the maxillary sinus shows another site for analysis when the dentition is missing. (From the private collection of Phil Levine, DDS, Pensacola, Fla.)

The hardness of enamel and its resistance to temperatures as high as 2000ºF mean that tooth identification may be useful in air crashes or forest fires. According to Sakoda, postmortem damage from decomposition and fire appear to be more frequently observed in the anterior teeth. [5] Using small and wide-angle radiography scattering, a structural reference for quantitative analysis of heat affected dental tissues has been developed. This nondestructive method determines local dentine/enamel alterations of crystalline shapes, alignment, and hydroxyapatite thickness to provide precise temperature estimation in victim identification. [6]

Handheld energy sources have been invaluable in recording dental identification from mass disasters or unidentified remains. Their 2-dimensional (2-D) images can be stored to a disk for later dental antemortem comparisons or entered into the database of the National Crime Information Center (NCIC) for missing person identification.

Technology may also influence dental investigators who occasionally collect data using rotational 3-D cone beam skull imaging. A preliminary study by Tardivo et al used 58 CT scans to assess 133 root mineralized canines. In a time of 20 minutes per tooth, pulp volume/total volume ratios of secondary dentin were measured with 100% accuracy in age and sex determination. [7] However, cost, equipment access, and maneuverability may mitigate the practicality of this technology. Currently, 2-D antemortem radiographs, digital or conventional, are prevalent in dental offices and therefore more appropriate when comparing to like postmortem images.

Previous
Next:

Dental Osteopathologies

Antemortem radiographs may show the presence of cysts: radicular, dentigerous, lateral periodontal, odontogenic keratocysts, calcifying odontogenic, globulomaxillary, aneurysmal, simple, and static. Although the presence of these lesions on postmortem radiographs may be very useful in some cases, reliance on postmortem films of these anomalies can be problematic because of their rapid decomposition and dehydration. Consequently, the dental investigator tends to rely on evidentiary bony exostoses (tori) (see the following image) and diseases affecting bone morphology and density.

Mandibular tori. (From the private collection of A Mandibular tori. (From the private collection of Allan Warnick, DDS, Detroit, Mich.)

Tori and bony exostoses may be singular or multilobulated and occur in either the maxilla or mandible. Paget disease radiographs reflect a "cotton wool" appearance of skull radiographs along with hypercementosis surrounding the teeth and enlarged maxillary ridges. Hyperparathyroidism with radiolucencies and loss of lamina dura is seen in the mandible.

Craniofacial dysostoses, mandibulofacial dysostoses, and dysostoses from Marfan and Down syndromes are examples of genetic- and chromosome-induced changes resulting in an extremely high vault of the maxilla along with narrow width and extended length of the arches. Malocclusion is common in such cases. The list of benign nonodontogenic tumors includes ossifying fibroma, fibrous dysplasia, osteoblastoma, osteoid osteoma, central giant cell granuloma, giant cell tumor, hemangioma of bone, idiopathic histiocytosis, and coronoid hyperplasia.

In summation, dental osteopathology has been categorized into the following:

  • Wear on teeth due to normal or abnormal use
  • Bacteria (caries, plaque, abscesses)
  • Atrophy of oral cavity contents (periodontal disease, plaque, premature tooth loss, aging)
  • Malignant tumors (rare in ancients) and nonmalignant (tori)
  • Accidental or purposeful tooth modification
  • Congenital and developmental anomalies [3]
Previous
Next:

Oral Pathologies

Methamphetamine and amphetamine use and abuse show pharmacokinetics and pharmacodynamics that may influence clinical tooth dissolution (see the following image). [8, 9]

pH drops in saliva, such as occurs with methamphet pH drops in saliva, such as occurs with methamphetamine use, coupled with decreased salivary flow from alpha-2 brain receptors, can destroy clinical tooth crowns, leaving dental forensic identification to tooth root morphology and surrounding bone trabeculations.

Bulimia and tetracycline use during tooth development leave their respective wear/discoloration indicators, and intravenous bisphosphonates have occasionally been implicated in mandibular, maxillary, or otic bone necrosis associated with osteoradionecrosis following head and neck radiation therapy.

See also Tooth Discoloration.

Previous
Next:

Identification of Remains

Historically, age and gender estimates in forensic and archaeologic investigations have involved analysis of cranial and pubic suture closure, numbers/charts reflecting presence of Howship lacunae in cortical bone, and radiographic aging of the femur and auricular surface. The accuracy of these and other procedures remains unclear.

Demirjian’s age estimate system uses 8 steps of tooth mineralization but has shown to be subject to varied regional development rates, thereby prompting Ohtani to pursue amino acid racemization. This age indicator begins at the time of death by measuring the rate of change of dentin L isomer to the D form. Although accurate to within 3 years, this method has limitations due to a requirement for control teeth, difficulty in separating dentin from other tooth parts, and fabricating a separation column. [10] Buchholz demonstrated how to obtain the exact birth year of victims born after 1942 using carbon-14. [11] He has used isotopic carbon analysis of developed teeth to determine precise age and obtain clues to the victim’s geographic origin.

Cardoso’s study of sex determination using deciduous crown formation confirms accuracy obstacles discovered by earlier investigators (ie, primary crown dimensions are less sexually dimorphic than permanent tooth dimensions, the degree of dimorphism within and among populations varies). [12]

The above studies of gender and age determination may be used as a general guide to victim identification but a more precise method is required. Assuming ante-mortem films can be obtained, comparisons to postmortem dental radiographs have long been used by investigators with consistent results.

The following radiographs demonstrate exact points of tooth comparison used by the odontologist:

Forensic dental comparison of 12 points on 3 teeth Forensic dental comparison of 12 points on 3 teeth. (From the private collection of Allan Warnick, DDS, Detroit, Mich.)
Postmortem forensic dental comparison of crowns, r Postmortem forensic dental comparison of crowns, restorations, bone levels, and endodontics. (From the private collection of Allan Warnick, DDS, Detroit, Mich.)
After 4 years, the relative points of comparison s After 4 years, the relative points of comparison still exist (arrows). (From the private collection of Allan Warnick, DDS, Detroit, Mich.)

Forensic odontology: identification in the absence of antemortem records

Mitochondrial DNA samples taken from human molar pulp chambers act as genetic sources and may be useful in identifying victims of natural disasters, explosions, and drowning. For example, when the Confederate submarine Hunley was retrieved off the South Carolina coast several years ago with the human remains of the crew still on board, one of the crew, Seaman Joseph Ridgaway, was identified using mitochondrial (mt) DNA by comparing his genome sequence to that of the exhumed remains of Elizabeth Joiner, his sister.

Serendipitously, researchers were able to identify the backgrounds of other crewmen, because many soldiers fighting for the Confederacy were foreign (the first regiment to sign up in Charleston was German). "When food is ingested, these isotopes become—and through life remain—deposited in teeth. Thus, by looking at the stable isotope composition in the men's teeth, which they developed when young, the researchers (could) determine if the men were born in the United States or, say, Europe." [13]

The Romanov family was assassinated and dumped down a mineshaft 12 miles north of Yekaterinburg. Later, the bodies of the royal family were retrieved: the bodies had been dismembered, with the faces smashed and sprinkled with sulfuric acid and reburied. DNA analysis played the key role in identifying the individuals by taking a sample from Prince Phillip, Duke of Edinburgh, a grandson of Victoria (Tsarina Alexandra's oldest sister). Because mtDNA requires matrilineal transmission, identification was confirmed.

One of these individuals was suspected to be Tsarina Alexandra Fyodorovna of Hesse, owing to the teeth showing amalgam restorations, a luxury at the time. The Czar's remains showed exceptional restorative dentistry as well, but confirmation of his identity was obtained from DNA obtained from his late brother, Grand Duke George Alexandrovich. Clouding the investigation was the discovery of several unidentified teeth at the burial site. The 2 missing children Alexei and Marie were located in another grave near the last family burial site.

Another controversial death involved that of Adolph Hitler in 1945. Nine months earlier, an attempt on his life had failed, but 5 skull radiographs were taken at a subsequent physical examination. In late April 1945, as Germany was collapsing, Hitler ordered that his body be doused with gasoline and burned following his and Eva Braun's suicides. The Russians recovered remains (see the images below) at his bunker, took radiographs, and when the US Military Intelligence Service compared the 1944 antemortem films with the postmortem films from the Soviet counterintelligence unit and Russian Federal Security Service, a positive identity was claimed.

The identification of Adolf Hitler. Left upper and The identification of Adolf Hitler. Left upper and lower maxillary bridge seen from the lingual; right upper-buccal (front) view of mandibular left bridge; and right lower-lingual (inside) view of mandibular bridge. Note the severe bone loss around the lower anterior teeth. (From the private collection of Allan Warnick, DDS, Detroit, Mich.)

Beginning in May 1945 and lasting over several years, the Russian KGB exhumed and reburied the remains at different locales. The initial Soviet films confirmed that the dentistry on a corpse at the bunker had mandibular anterior bone loss, mandibular bridge #27-29 with #30 cantilevered, and a #9 "window crown." But a 4-9 unit maxillary bridge (depending on the investigator) was not corroborated. Perrier used computer-enhanced images of Hitler's teeth, concluding there was no doubt about the certainty of identification, [14] but Dorion compared thousands of close-up photos of the Fuhrer and concluded just the opposite, citing spacing, endodontics, and a porcelain crown mandibular right as evidence. [15]

There is agreement, however, about Hitler's severe periodontal bone loss in the mandibular anteriors, which was verified in postmortem radiographs and which may have accounted for irregular tooth spacing. Even recent skull and blood samples from the Russian state archive were analyzed, showing the remains to be those of a woman 20-40 years old (Eva Braun's DNA was too degraded to show a full range of markers). Finally, as reported by his pilot, Hitler ordered antemortem dental radiographs of all upper-level Nazis be flown to an unknown destination. Only the memories of his dentist and assistant were available to investigators.

Previous
Next:

DNA Sampling

Following up on trace mineral analysis of the Hunley project and to determine the identity and relatedness of remains at Fort Niagara, Jennifer Byrnes measured strontium levels in bones and teeth with portable x-ray fluorescence. [16] But bone is constantly remodeling, and tooth absorption levels reflect uptake only during formation of deciduous or permanent dentition. Ms. Byrnes concluded that identification using mtDNA extracted from tooth pulps was more accurate than measuring trace mineral levels. [16]

Despite the accuracy of mtDNA identification, currently, mtDNA analysis and sensitivity are usually reserved for trace amounts of sample, as in antiquated or charred remains, [17] due to time, expense, and the select few laboratories which test mtDNA. Thus, nuclear DNA typing has become the most widely used technique. The double helix strands contain chromosomes averaging 100 million base pairs of nucleotides, which combine the unwieldy numbers into STRs (short tandem repeats). The DNA can be amplified to develop a profile through the polymerase chain reaction (PCR).

The Combined DNA Index System (CODIS) lists probability identities of 13 standardized STRs, but the amelogenin gene is of particular interest to the odontologist, as it is actually the gene for tooth pulp (and sex). Although nuclear DNA testing is very specific, Ashley noted that errors in gathering DNA evidence may develop from soil or blood contamination, infrequently changing gloves, storage in plastic bags (bacteria), lack of refrigeration, and the amount of DNA, which affects band intensity, or a second person's DNA. [18]

Gum, recent apple bites, dental impression wafers, saliva, licked stamps, toothbrushes, and envelopes may capture low quantities of DNA. Even bacterial infections once thought to contaminate assays can still reveal one-time oral infections. It was assumed that dried out oral hygiene materials were of no evidentiary value, but a study showed that 5-bristle toothbrushes all exhibited excellent DNA samples. Acrylic in 200-day-old dental prostheses has also provided researchers with sex and tooth-pulp determination by amplifying segments of the amelogenin gene.

Researchers at major universities and corporations may soon offer fast inexpensive single-strand DNA genome sequencing using nanopores. [19] The effect of this specific identification technology on odontologic methods remains to be seen.

Previous
Next:

Bite-Mark Evidence

In 1954, Doyle v Texas was the first modern-day bite-mark conviction that was upheld by the Texas Court of Criminal Appeals; that bite was in cheese and not human skin. [20] JJ Layton also pointed to incisal and labial tooth prints in cheese resulting in a London, England, conviction. [21]

Overlay techniques reflect hollow-volume perimeters of biting surfaces; transillumination, scanning electron microscopy, reflective ultraviolet photography, and computer-generated and enhanced photography may be useful, but these modalities still depend on the presumption that the individual's tooth size, shape, and position are unique and also that the material bitten accurately conveys the impression. Such technologies may help to verify human bite marks, and acting together, their presence in the courtroom can be convincing. Whether they meet the challenge of certainty presented by a well-prepared defense attorney is another matter. Daubert's 4 classic parameters of peer review, known error rate, adequate testing, and general acceptance are regarded as the standard for bite-mark reliability in court, and Bowers has tried to minimize bite-mark error by categorizing types of photographic distortion and position before the investigator resizes or enhances the image. [22]

Beyond Daubert, Wood in Canada has noted that the National Institute of Forensic Science suggests an algorithm to replace current standards of terminology, which are based on consensus opinion. [23] Even peer-reviewed journals vary in their degree of scientific agreement. Therefore, judicial gate-keeping must account for lack of courtroom scientific background by confining testimony regarding bite marks to the following questions [23] :

  • Is the patterned injury a bite mark, or is the material presented sufficient enough to make a decision?
  • Is the material presented of evidentiary value without further investigation?
  • Can the suspected dentition be excluded or not from having made the bite mark?

A 2009 National Academy of Sciences report criticized bite-mark evidence [24] : "There is no science on the reproducibility of the different methods of analysis that lead to conclusions about the probability of a match...."

The National Academy of Sciences (NAS) report further states, “Even when using the American Board of Forensic Odontology (ABFO) guidelines, different experts provide widely differing results and a high percentage of false positive matches of bitemarks using controlled comparison studies.” [25] In addition, the report completely neglected to mention that bite-mark analysis as an appropriate methodology in criminal investigations or that when properly applied, bite-mark analysis contributes to successful prosecutions in criminal assault and abuse cases. [26] With such limited scientific basis, it is valid to question how bite-mark comparison has reached the level of acceptance that it has. [27] Incarceration of innocent people associated with bite-mark evidence has resulted in an added level of scientific scrutiny. [28]

The newly formed Strategic Litigation Unit of The Innocence Project questions the admissibility of bite-mark evidence but is dedicated to learning and discussing the best ways of challenging such evidence. [29] If undisciplined use of bite-mark evidence continues, postconviction defense counsels are advised to critically evaluate any case involving bite-mark evidence in where there exists the potential for innocence and to be cautious to collect all the original documentation. [30]

ABFO terms such as “reasonable medical certainty”, “high degree of certainty”, “no doubt in my mind”, “in my opinion”, “the suspect is the biter”, “beyond a reasonable doubt”, and “99% certainty” may bring suspicion on the guidelines themselves.

Publicity surrounding the 1970s Tallahassee Chi Omega murders featured bite-mark evidence as the deciding factor in the conviction of Theodore Bundy (see the following images).

Wax bite exemplar of Ted Bundy's lower front teeth Wax bite exemplar of Ted Bundy's lower front teeth.
Frontal view of Ted Bundy's teeth. Frontal view of Ted Bundy's teeth.
The edges of Ted Bundy's teeth #22 through #27 mad The edges of Ted Bundy's teeth #22 through #27 made as a compound overlay via digital compositing methods.
Digital superimposition of original hand-drawn ove Digital superimposition of original hand-drawn overlay onto Ted Bundy's bite mark.
The buttock of Lisa Levy after having been bitten The buttock of Lisa Levy after having been bitten in different directions. Only the unique arrangement of Bundy's lower teeth (as shown in the wax imprint image) made it possible to place the overlay as shown.

Note the unique tooth marks (see the images above) that were left from Bundy's actual double bite marks on Lisa Levy's buttocks. Not shown was the result of an attempt to corroborate these findings when Dr. Souviron asked the guard to give Bundy an apple. After his first bite, it was taken for an impression. The attempt was described as a "partial success," because the apple had distorted between the time of the bite and taking the impression.

The Bundy cases’ notoriety promoted the “revelation” that tooth and fingerprints were equally unique and therefore reliable. Although untrue, it has been easier for attorneys to argue and jurors to visualize such cases in court. Computerized overlays and build-ups of teeth can be quite dramatic in court as the dental model's incisal edges are slowly lowered to "match" the marks on a photo. Whether these marks were tooth borne, insect, chemical, pathologic, or trauma is the question.

Controversies

Over a period of years, controversy has ensued, resulting in the 2008 Saks and Faigman article that citied 8 cases in which there was disagreement among forensic odontologists as to whether the bite marks were from the accused or even human in origin. [31] The viscoelastic nature of the victim's epidermis may have altered a reproducible biting force. In addition, the associated bruising, edema, vessel rupture, and inflammation may have produced indistinct results. [31]

Souviron has pointed out that refrigeration time, temperature, humidity, light, and gravity are further variables that affect bite marks. [32] Enhancement of the traumatic lesion due to victim dehydration, gravity's tendency to move blood from normal tissue but not from an injury, the questionable theory of collecting bite-mark evidence as soon as possible, along with inconsistencies of photographs and radiographs are factors which further cloud the science. Kieser concluded that "more than 150 years of developments in bite mark evidence still leaves us without some sort of consensual basis to decide whether or not bite mark evidence should be admitted." [33] Plourd allows that although there is evidence that a person's teeth can be unique, what little scientific evidence that does exist supports the conclusion that crime-related bite marks are grossly distorted, inaccurate, and therefore unreliable as a method of identification. [24]

Moreover, psychological bias may exist as the investigator interprets odontologic evidence with the desire to conform to the beliefs and perceptions of others. Even terms such as “victim” or “perpetrator” may lead to confirmation bias by the investigator. Motivational or cognitive effects such as the following may challenge the objectivity of the odontologist’s testimony [34] :

  • Hawthorne effect - Tendency to perform when one is in the spotlight
  • Contrast - Tendency to rationalize weak evidence associations over time
  • Overconfidence - Jury’s tendency to be influenced by expert’s demeanor

The following are examples and problems associated with odontology's attempt to bring credence to bite-mark evidence: Photos of bite marks on a body, impressions, and casts using Adobe Photoshop computerized reproductions; spectroscopic, infrared reproductions; transillumination; and photography with 2 calibrated, perpendicular reference rulers are recognized instruments used in gathering forensic data. However, although incisal painting of these reproductions, along with polyline measurements of mesial distal tooth widths or rotation and interarch canine distances appear reasonable scientific procedures, they may have been distorted by alginate impression shrinkage, or postmortem decomposition. [35, 36]

Even if photographed immediately, 3-dimensional (3-D) bite marks on a 2-D photograph will be associated with changes in color and spatial relations; skin associated with curved surfaces is an unreliable impression medium and distorts more easily than biting flat surfaces. [37] A struggling victim and jaw thrust of the suspect during the attack are additional variables that obscure evidence.

Some investigators feel that the value in bite-mark evidence lies in the likelihood of identifying those not involved through missing dentition rather than a positive identification, such as in the case of a wrongfully incarcerated Milwaukee man who was convicted on bite-mark evidence but which DNA evidence refuted. This and another similar case have caused some odontologists to voluntarily retract previous testimony.

The American Board of Forensic Odontology (ABFO) is considering a paradigm review regarding bite-mark evidence, wherein the terms "degree of certainty, probable/possible" have clouded the "beyond a reasonable doubt" legal presentation. The term "match" with regard to bite-mark evidence may eventually be replaced with a suspect being "one who cannot be excluded as a person of interest." Therefore, bite-mark evidence by itself appears to have limited use in positive identification, but it may serve along with a constellation of factors to supplement a position presented in court.

A study of evidentiary court challenges to fingerprints, handwriting, firearms, tool marks, ballistics, and forensic documents found that the largest proportion of restrictions because of reliability was that of forensic odontology. “Unsatisfactory, careless, and troubling” were words used to describe court criticisms of all evidence admissibility, which may have prompted Vermont Senator Leahy to propose the “Criminal Justice and Forensic Science Reform Act of 2011.” That initiative was supported by the National Association of Criminal Defense Lawyers at its June 2011 meeting, with an agenda including a 3-day seminar on forensic odontology. [38] An interview with the past President of the AAFS revealed some congressional hesitation in support of Senator Leahy’s proposal.

Even more comprehensive regulation is being considered as the American National Standards Institute (ANSI) has approved American Dental Association (ADA) specification no. 1058 for forensic dental data set as an American national standard. Their goal is to standardize methods and nomenclature ("Informatics") in dental data collection for entry in an electronic format. [39]

A review of the 2012 American Academy of Forensic Sciences (AAFS) Annual Scientific Meeting Proceedings shows a variety of studies regarding validity/reliability of bite mark evidence. By itself, bite mark evidence is viewed by some as poor-to-nonexistent science. [40] Others attempt to gain forensic credibility by classifying the degree of bite mark quality. [41] Convictions have been obtained based solely on models along with 20-year-old bite mark photographs, perhaps subjected to light (“white balance”) color and lens aberrations. [42] A recent study of bite mark characteristics using live subjects showed all volunteers but one having no indentations after 2 hours healing. The “biting” force required to produce a 24-hour indentation ranged from 60-235 lbs. [43]

Previous
Next:

Dental Charting

Charting teeth for identification is usually subject to the available forms in the medical examiner's office and may include the Universal Numbering, Palmer Notation, or FDI (Federation Dentaire Internationale) World Dental Federation numbering methods. Of the 3 systems, the Universal seems to be most widely accepted (see the images below). In this case, the teeth, starting with the maxillary right 3rd molar, are designated #1-16, ending with the maxillary left 3rd molar; and #17-32 from the mandibular left 3rd molar, ending with #32, the mandibular right 3rd molar.

Antemortem dental record. Antemortem dental record.
Postmortem dental record. Postmortem dental record.

A continuing challenge in this area is to standardize all record keeping. The forms used at various schools, reading radiographs, and conducting clinical dental examinations may hinder consistent record keeping. In 1984, the American Board of Forensic Odontology (ABFO) guidelines sought to clear up this confusion by proclaiming the Universal Numbering System as the recommended method for dental charting. Unfortunately, the "button out" versus "button in" orientation may reflect military versus school protocols for reading conventional films and recording clinical findings. Digital radiographs, whether hand held or stationary, should help speed the charting process.

The forms used by the Armed Forces Institute of Pathology (AFIP) are compatible for entry in the Federal Bureau of Investigation (FBI)/National Crime Information Center (NCIC). Antemortem radiographs may be placed next to the postmortem films in the courtroom such that a complete set of films must be taken.

Previous
Next:

Challenges

The primary challenge in evidence gathering for forensic dentistry consists of standardizing investigator collection methods. As previously noted, errors in collection/interpretation can be found in everything from bite marks to radiographs to DNA (see Bite-Mark Evidence). High-profile court cases, for example, bring awareness to such legal vulnerability.

Avoiding the following terms may help reduce legal confusion in the courtroom:

  • The statement “based on my training and experience” made at the beginning of expert testimony may lead to the opposing attorney’s assumption that the rest of the sentence is speculation in justifying a conclusion. [44]
  • “Theory and possibility” are expansive terms reflecting a degree of certainty not usually recognized in environmental forensic science but found in religion and philosophy.

A Bill introduced by Senator Patrick Leahy and co-sponsors in January 2011 was intended to establish an Office of Forensic Science and a Forensic Science Board as a means to strengthen and promote confidence in the criminal justice system. Their initial goal was to ensure consistency and scientific validity in forensic testing until they encountered NAS criticism of each forensic discipline area’s reliance on Scientific Working Group (SWG) guidelines administered by NIST (National Institute of Standards and Technology). NAS maintained that SWG guidelines and best practices were not independent enough in separating Forensic Science from Law Enforcement. Thus in February 2014, and in accord with the Department of Justice, the funded non-regulatory NIST’s task of ensuring forensic consistency and scientific validity was turned over to OSAC, the Organization of Scientific Area Committees. Its organizational chart consists of 5 Scientific Area Committees (SAC) reporting to a Forensic ScienceStandards Board (FSSO), plus Legal Resource, and 23 forensic subcommittees as well. The 402 members named to the FSSO will coordinate development of forensic community standards and guidelines. Specific operational needs such as for DNA or Digital Evidence may cause the DOJ to retain a few SWG guidelines but the majority of SWG guidelines and best practices will be abandoned in favor of scrutiny by both public vetted Quality Infrastructure Committees and Legal Resource Committees (LRCs) for Professional Code of Ethics adherence.

Persson at the University of Linkoping, Sweden, [45] and Thali et al at the University of Berne, Switzerland, [46] have tried to mitigate errors in forensic evidence gathering by developing a virtual imaging system whose multislice computed tomography (MSCT) images can be opened and closed without distorting evidence. Their 3-dimensional (3-D), color-enhanced, 1+ mm–resolution, rotational images are captured by a "flash" scan, which can record up to 24,000 body slices in seconds.

As pointed out at the end of the Radiology and Forensic Odontology section, the expense and logistical problems associated with 3-D computed tomography (CT) scans make 2-D images more efficient in dental identification. Still, the value to dental identification is the 3-D, rotational, reproducible images of the oral cavity. Antemortem radiographs, whether digital or conventional, can easily be compared to postmortem images of crowns, bridges, amalgam, or composite restorations, prostheses, tooth and root angulations, trabecular bone patterns, and anatomic landmarks.

The International Organization of Police Chiefs (IAPC) Committee to Identify the Missing has proposed registering all dental implants. An identification number plus the manufacturer, type, and year could reduce the number of consulting dentists in forensic identifications from 165,000 to the approximately 200 who use that manufacturer’s appliance. [47]

Early oral CT scan interferences (streaking) were due to dental amalgam or crown prostheses and have been replaced with color-coded density assignments to both metals and composite restorations. Although these technologic advances are of inestimable time value in postmortem dental identification following disasters such as the 2004 tsunami or 2010 Haitian earthquake, [46] they are even more important as a reproducible evidence source.

Forensic odontologists should be aware of the changing courtroom atmosphere and act accordingly before presenting evidence. The "CSI" effect from television shows has brought unrealistic expectations from non–science-oriented juries seeking absolute proof of forensic science. Knight, Durnal, and Robbers in separate studies have shown awareness and possible misguided expectations of certainty or "matches" from DNA or fingerprints. [48] Even negative witnesses have been brought in to explain the problems associated with seemingly conclusive evidence. In addition, criminals are becoming aware of using bleach to kill DNA, taping envelopes, and wearing gloves as methods of subverting crime scene investigation.

The dental investigator has been accustomed to showing the antemortem and postmortem comparisons of teeth, restorations, and maybe bone anomalies, as conclusive evidence in forensic identification. Perhaps the now skeptical juror will need additional science. Or maybe the criminal, anticipating dentistry's role in identification, will attempt to obviate that possibility with preemptive destruction of dental evidence.

Previous
Next:

Conclusion

It is important to recognize the value of dental forensic identification from the early ancients to the present. From natural disasters to atrocities to mysterious disappearances, dental remains have been a universally used tool to determine identification, lifestyles, culture, and societies. Forensic dentistry remains an efficient means of recognizing the identity of the deceased.

The 66th Annual Scientific Meeting of The American Academy of Forensic Sciences (AAFS) was held in Seattle Washington on 17-22 February, 2014. National Academy of Sciences (NAS) scientific areas of “analytical” or hard evidence (DNA, chemical, materials, fire, explosives) were featured sections, as well as odontology, which leaned more toward “pattern/experience” or soft evidence (fingerprints, bite marks, blood stain patterns.). [49] The American Board of Forensic Odontology (ABFO) has tried mitigating NAS validity concerns with the odontology section by updating standards, guidelines, human bite-mark classification, certification, and, especially corroboration/challenge of several expert opinions regarding reproducibility of bite-mark evidence. [50, 51]

Additionally, current presentations attempt to enhance the validity of bite marks by using technology, such as the following examples: [52, 53, 54, 55, 56]

  • To correct crime scene camera angles
  • GNU Image Manipulation to fabricate bite-mark overlays
  • Three-dimensional bite-mark analysis
  • Recognizing positional distortions in hollow-volume overlays
  • Simulated bites on live volunteers with and without high-speed videography
  • Cone-beam computed tomography imaging
  • Password-protected technology to transfer ante mortem records via images attached to texts, emails, smartphones, computer tablets, or laptop computers

Whether such attempts to blunt the NAS’s criticism that bite marks are of limited evidentiary value remain a question. However, to ignore tooth-mark evidence and set a perpetrator free is in no one’s interest.

Skin as the recording medium is viscoelastic in nature and, coupled with a struggle, makes reproducibility impossible. Wright, in his presentation, states that, “the uniqueness of the human dentition as it relates to human bitemarks in living skin has not been proven in large open-population studies.” (In an earlier presentation, he had referred to the subjective term, “high-quality” bite-mark evidence without defining the term or differentiating high quality from medium-high quality or medium quality.) [56]

Page, in a study of 15 odontologists with varying opinions of the 6 images they were shown concluded that the assessment criteria were so disparate that the NAS’ position of odontology bite-mark evidence in forensics was “fair at best.” [57] Aleksandravicius, when comparing mechanical dental clamping simulations to actual bites during violence, concluded that, “it is difficult and may be impossible, to fully reconcile the reproducible science.” [58]

Therefore, as suggested by other presenters, ABFO may do well to accept its role as support for and reliance on other AAFS disciplines.

A study by Roberts et al compared the effectiveness of swabbing and flossing as a means of recovering spermatozoa from the oral cavity following sexual assault. Swabbing was found to be more effective than flossing, so long as the collection time of postcoital interval (PCI) was 1.5-12 hours. At 24 hours, the 2 methods were equally effective in terms of the percentage of subjects from whom spermatozoa was recovered, as well as semen concentration. If PCI is longer than 24 hours floss may present more information than swabbing. However, degradation of spermatozoa is subject various factors that are difficult to control, including rinsing, toothbrushing habits, eating, and drinking. Other variables affecting the study included expectoration, swallowing the semen, the victim’s postassault hygiene activities, delays, and avoidance of reporting. Although the 2 methods combine to increase the percentage of subjects with recoverable spermatozoa, the report was not controlled. The wide activitydisparitybetween the subjects also compromised the study’s results. [59]

Speakers from recognized reproducible-evidence disciplines might provide the odontology section with a reliable appreciation for DNA collection, toxicology analysis, entomology, veterinary medicine, and chemicals, among others. Combining objective or hard evidence with bite marks may be useful in mitigating criticism of bite marks in this team approach. [60, 61]

Although bite-mark evidence does have a place in the court system, it should be used with a constellation of factors in which evidence has been gathered with the utmost care to prevent misidentification. Thus, in the interest of objectivity, as well as in anticipation of court challenges, precautions in data collection must be rigidly observed. Therefore, the definition of forensic dentistry presented initially in this article should be amended from "the study and practice of aspects of dentistry that are relevant to legal problems" to include the more thorough phrasing of the ABFO, "the careful and proper handling of dental evidence for legal matters."

Previous
Next:

Additional Resources

The following resources ares recommended for more detailed information regarding forensic dentistry:

  • Bowers CM. Forensic Dental Evidence: An Investigator's Handbook. San Diego, Calif: Academic Press; 2004.
  • Dorion RBJ, ed. Bitemark Evidence. New York, NY: Marcel Dekker; 2005.
  • Fixott RH, ed. The Dental Clinics of North America (Forensic Odontology). Philadelphia, Pa: WB Saunders Company; 2001:45(2).
  • Thali MJ, Dirnhofer R, Vock P, eds. The Virtopsy Approach: 3D Optical and Radiological Scanning and Reconstruction in Forensic Medicine. Boca Raton, Fla: CRC Press; 2009.
  • Turner CG, II, Eder JF. Dental pathology, wear, and diet in a hunting and gathering forest-dwelling group: the Batak people of Palawan Island, the Philippines. In: Harris EF, ed. Dental Anthropology: A Publication of the Dental Anthropology Association. Memphis, Tenn: University of Tennessee; 2006:19(1). Available at: http://anthropology.osu.edu/DAA/back%20issues/DA%20Vol%2019%201.pdf. Accessed January 16, 2011.
Previous