Novel Method of Measuring the Time of Death on the Tooth

Novel Method of Measuring the Time of Death on the Tooth

Novel Method of Measuring the Time of Death on the Tooth - Based on Liquid Contents, Reflection Spectra and Color: First also Reference-Independent Measurement and Analysis Method due to Reversibility of Drying and Absorption of Liquid or Water



As part of my scientific research on dental tissues and electromagnetic radiation and my work as an innovator, process and system developer, I have considered what dental processes can still be used for. I quickly came across the field of estimation of the time of death.

In addition, as a studied dentist, who is accustomed to high precision, I have found that in this field only a relatively imprecise estimate is conceivable due to intra- and inter-individual influences.

Previously known forensic-medical possibilities for estimating the time of death must inevitably be inaccurate. I wondered whether the limitations are insurmountable, or whether there could be a specific process and a technology, which could have a high level of accuracy and a statement after longer times in this forensic field.

The problem that has been inherent in the methods so far lies ‒ in my opinion ‒ in the dispersion of data, which is inherent in methods or tissues: the general scientific prerequisite for the use of a method for estimation the time of death is the existence of a process that is triggered by death and must be descriptive and differentiated in stages (e.g. rigor and livor mortis, putrefaction) or values (see body cooling method). In order to classify these stages or values, the results of previous studies were always needed. The assessment and estimation in the specific application is carried out in the light of previous studies. Without exception, all processes described in the literature in connection with the time of death estimations are highly individual, contain an intra- and inter-individual dispersion of reference values/stages/phenomena, are irreversible, so cannot be reversed, and without exception all methods use reference values (e.g. temperature) or reference descriptions. An assessment of a current time of death against the background of scattered references can be imprecise at best.

Quite different, as you will read in the book, the novel approaches and developed methods. Because not only one process, but above all the measurable processes that a tooth goes through during drying are very special and unique in their character. Read about the advantages and the special character of the usable processes and perhaps even the first reference-independent method of analysis or measurement in the natural sciences.

You will find out what this ultimately means and how you can measure processes with which systems and avoid errors in colorimetrics and spectrophotometry at teeth. Join me on a path that will introduce you to the color theory, to the high-precision spectral analysis, colorimetry and liquid content measurement, to the topic of estimation of the time of death or, as we might call it in the future, death time measurement, and other novel and innovative technology-based methods. 

I would be very pleased if you were as fascinated by the path, just as the way fascinated me when I first walked this path; and I would be pleased if you are grabbed by the subject just as it grabbed me and still captivates me.

July 2000                                                                                                    André Hoffmann


The time of death is of considerable importance for investigations, is often one and sometimes the central key to solving criminal cases. It gives investigators a temporal framework and allows to reconstruct the chronology of the crime and, by checking of alibis, to narrow down the circle of suspects, excluding some and concentrating on others; and it can sometimes contribute to the reconstruction of the course of events. The time of death is also relevant in cases of natural death for the family register entry, insurance or succession and the request of the relatives for knowledge of the exact time or hour of death (see chapter 2).

But according to the author’s analysis, one of the greatest problems in forensic medicine must be the precise estimation of the time of death and estimations after two or three days ‒ it seems to be extremely difficult or impossible. In addition, there are a lot of influencing factors that may be unknown in the specific case. However, a number of factors can seriously influence the results or make it impossible to determine the time of death. All classical methods are limited to the first, second or third day after the onset of death. Such methods, which are based on such highly individual processes, contain uncertainty factors, intra- and inter-individual inaccuracies, which do not generally make estimations simple. In principle, there should be a need for new methods if a post-mortem interval is to be determined more precisely or also after longer times.

If the precision of the time statement is higher, the criminal investigation can be more targeted, more successful and economical.

The event of death and the subsequent onset are associated with very complex processes that alter a corpse and its tissues. If it would be possible to find a process of a particular tissue that behaves precisely like a clockwork and if it were also possible to set the time and condition state back to the moment of death, if the clock could run anew again and if it would also be possible to re-run the past time with all conditions states after the onset of death once again in real time at the same (identical) individual or object of investigation to be examined and if it is not just one clock, but several clocks of different complementary readings, it would be the perfect and most accurate method of measuring the time of death.

The author of the present work had observed that human teeth are much brighter and have another color (valuehuesaturation) as well translucency ‒ less translucent and more opaque ‒ after death than in life. He sees a fundamental possibility in the use of processes ‒ that he has measured and analyzed at drying and rehydrating teeth ‒ and presented this novel method, for the first time. In addition, it is also the first reference independence method ‒ perhaps even the first reference-independent method of analysis or measurement in the natural sciences ‒ that does not require reference values obtained from other comparable samples (e.g. nomogram). In order to stay with the analogy, the tooth with its liquid has some clockworks and the measuring system provides also the clock face and hand or the display. The reversibility of the processes allows simulating and bypassing or eliminating inter-individual and intra-individual influencing factors ‒ for the first time.


2. Literature Review


There is a certain time and precision gap between the classic estimation of the time of death and the determination of the time of lying. If a distinction is made between the determination of the time of death (using processes associated with body tissues that occur immediately as a result of death) and the corpse laying time estimation (using processes that result from the lying of a dead body in a specific location), the possibility of determination the time of death ends after one to three days at the latest. Influencing factors such as the physical conditions or condition of the body, cause of death, initial temperature of the body at the time of death, diseases, germ colonization, location, ambient temperature, sunlight, ventilation, moisture, animal feeding, displacement of the body and much, much more are likely to be decisive for the course of post mortem changes and the signs of death. Influencing factors that are not known or have changed may lead to incorrect results. If the death is more than 3 days ago, no time of death determination is possible.

In principle, there is a need for new methods if a time of death determination is to be made more accurate or even after longer periods of time than described post mortem.  

All previous methods are based on irreversible processes. In this respect, a method based on reversible processes could be advantageous and help to avoid or eliminate inter-individual scattering problems and intra-individual difficulties.


2.2 Applications of Spectrophotometry and Colorimetrics
      in Forensic Medicine; Drying and Color

According to the authorʼs opinion, color science and spectral analysis are likely to be underestimated by forensic medicine. But they should be fundamental. Perhaps the number of few studies with spectrophotometers or colorimeters could show little interest or knowledge of the potential and leads to wasted diagnostic options in any case: however, measurements were carried out on hair (Bohnert et al. 1998), artificially generated haematomas (Lins and Hamper 1970, Klein et al. 1992 and 1996), forensic relevant changes or bruises (Lins 1975, Trujillo et al. 1996, Bohnert et al. 2000), in connection with haemoglobin (Siek et al. 1984), on skin of living (Lins 1969) and dead (Lins 1968), green discoloration (Lins and Kutschera 1974), post-mortem pallor, lividity or hypostasis (Vanezis 1991, Vanezis and Trujillo 1996, Schaefer 2000), livores mortis (Schuller et al. 1987 and 1988, Kaatsch et al. 1993 and 1994), material, such as blood (Lins and Blazek 1982, Rommeiß et al. 2000) as well as white powder of different composition (Bohnert and Werp 1999).

Drying Materials become brighter and change their color with the change in liquid content. This phenomenon can be observed in dry and wet textile fabric, on the more or less seawater-influenced sandy beach, at drying cement, lime or gypsum and depending on the weather at clay tiles or garden soil, and paint shows a different color effect before and after drying. Even rain clouds look different from the brighter and friendlier cumulus clouds of a beautiful summer day.

For the first time, the author of the present work had described a method for measuring the time of death on the basis of dental drying. Furthermore, he is the first to investigate the relationship between dental liquid content and tooth color colorimetrically and spectrophotometrically and to systematically research tooth color with high-precision measurement systems and high-precision positioning systems.



André Hoffmann systematically researched the tooth color at human teeth and dental shade guides with high-precision measuring systems and high-precision positioning system in vitro with highest precision. Due to this basic scientific research, he was able to quantify and isolate manifold factors influencing the color of teeth. These include, for example, the light or measuring light and the type of light (illuminant) and illumination and color temperature, the optical beam path of the light or the measuring geometry, the observation angle (2°, 10°), the size of the measuring surface, and measuring opening, the gloss effect, the liquid content (with scientific evidence of the relationship between liquid content and tooth color), effect of drying, moisture and rehydration, the correlation between the liquid content and the gloss effect, the subjectivity of visual subjective shade matching, crown curvature, type of system (spectrophotometer, tristimulus colorimeter), measuring mode (contact or non-contact), system-object-relation, positioning, repeatability or reproducibility, lens shift, displacement between sample and measuring surface and further intra- and interindividual factors. In addition, subjective-visual determinations and objectified measurements were examined in subjective-objective comparisons using color coordinates comparisons. All these influencing factors are investigated on moist, drying, drier (various specific dehydration and rehydration states) and dry teeth based on the brightness (L*), on color measurement values, such as a*, b* (CIELAB), C*, h, (CIELCH), ΔE, the metamerism index, spectral values and curves, tabs of dental shade guides and tooth color spaces

As part of this exploration, phenomena (e.g. changes and breaks in behaviour as well as highly individual developments in color values, paradoxes between the values of subjective determination using tooth shade patterns and the values of objective measurements) were identified; and insights into the very complex color dynamics through dehydration and rehydration were shown (up to more than >8 days). The development of the individual color measurement values was based on the liquid flow through the tooth and its tissues, in particular during drying and rehydration, and gave information about dynamics and the temporal extent of these processes.

On the basis of this data, Hoffmann had developed several methods for research and practice, suggestions for feasible innovations, such as monitoring of dental treatment to protect against pulp damage based on drying, and reconstructing the color of naturally moist teeth on those that have already dried, the identification of the living and the dead, human and animals via the “dental fingerprint” and a novel method of measuring the time of death for forensic medicine.

He also described a time limit of drying up to which relatively natural, suitable color values and shade matching results can be obtained and after which no color determination should be carried out; and he established the rehydration time after the end of the drying or dental treatment, which must be waited in order to regain a natural tooth color and to get correct values and results again. 

His findings also show that teeth are able to store information, for example, on the condition (liquid content, color values) and about the time within the drying and fluid reabsorption chronology. The author articulates a “dental chronometer” (“tooth clock”), “dental data storage” (“tooth data storage”) and a “dental memory” (“tooth memory”) and believes that significant progress in this area may include and could be achieved via a neural network for color measurement apparatus.


First Systematic Research and Analysis of the Tooth Color and Influencing Factors