Forensic Biomechanics and Human Injury: Criminal and Civil Applications - An Engineering Approach PDF

Preface 

There are many reasons why people write books. Our intent for writing this book is threefold. The first reason is to bring together information about the strength of biological materials from a variety of sources in a concise, comprehensive manner that is readily accessible to the reader or practitioner. Most of the information on the characteristics of biological materials, from an engineering standpoint, is difficult to find unless the reader has a fairly comprehensive library or does a significant amount of research. A considerable amount of the information exists in an outdated published form. Some of the information must be gleaned from animal studies simply because it is not available and tests have not been performed on humans. The reason for the lack of data on some human properties is simply that those studies could not be performed on humans. There is insufficient concise information on the subject in one text that is readily accessible to the investigator without performing extensive searches. In order to find some of the information, multiple sources from biology, anatomy, strength of materials, and medicine must be researched.

Let us turn for a moment to the topic of animal studies and why they are appropriate in our context. Animal studies have been utilized to determine the characteristics of scientific scrutiny in many forms, including the response to chemicals and carcinogens to which it would be inappropriate to subject humans. In our context, we simply include animal studies to correlate the similarities of the physical properties of various tissues to the human anatomy. When data for humans are not available, the correlations we have included afford the investigator a reasonable range of values of the characteristics of the particular tissue.

The second reason for writing this book is to educate the public, and in particular, engineers, attorneys, and judges, on the methodologies utilized to compute the forces, stresses, and energies required to produce injury to the human body. The calculations are actually quite simple. The trick is to determine how to apply the equations to the human body with relatively accurate dimensions and material strength characteristics to properly model the forces and stresses on the particular body part resulting from a particular incident. The intent is also to argue the simple fact that biomechanical engineers are the most capable individuals to perform these calculations. Again, let us emphasize that biomechanics is not a science of diagnosis but rather a science of causality and correlation to injury.

The third reason is to allow a relatively inexperienced person a method to perform the calculations, which may be especially true for a criminal investigator who is given the task to assign blame for the incident. The criminal investigator may need to perform some basic calculations to assess whether an incident should be included in the category of criminality or not. As an example, it may be alleged that the injuries suffered in a homicide case are due to a fall down a staircase. Some basic calculations may yield a completely different scenario in which it may be shown that the injuries could not have been created by a fall but rather by multiple blunt trauma to the body. Another example of a criminal case may involve a broken tibia alleged to be caused by the fall of a female. Calculations may show the injury to have actually resulted from physical abuse by a boyfriend or husband. A third example may involve shaken baby syndrome by a guardian in which it was alleged that the baby simply fell on the floor. Of course, in the case of injury or death, medical imaging or an autopsy would validate such findings of the forensic biomechanical investigator. All the parts of the puzzle must fit together in a cohesive manner. In this context, we have produced a variety of examples to compute the damaging events. Furthermore, we have included some calculations into which the investigator can easily plug typical values of known data and calculate the unknown. The pertinent equations are already included in the calculations with some typical values. Here, the investigator only needs to change certain parameters to fit his application. The parameters that may need to be entered to fit the particular case are found in the applicable sections of the book.

By writing this book in a relatively simple manner, without the complex medical terminology and anatomical description found in most treatises, we hope to educate and elucidate practitioners on the subject of injury to humans. Some mathematics and terminology are required to properly comprehend the subject matter, which is especially true of medical terms that confound most of us. We hope that the medical terminology encountered from the description by doctors will mostly be found in this text without the need to perform further searches. We have, however, simplified the material substantially and allowed the reader the opportunity to investigate how and under what conditions humans get hurt. Much of the medical terminology on the minor components of the human anatomy has been disregarded because we are looking at the major or most common types of trauma that occur. For example, we do not address the forces that may cause a broken toe because that type of injury can occur simply by stubbing the toe against an object while walking.