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Forensic Sciences: Injury Causation: A Primer Glenn N. Wagner Chief Medical Examiner, County of San Diego San Diego, CA

The CSI TV series has done much to promote the interactions of the crime laboratory with the forensic pathology practiced in the medical examiner's or coroner's office. Both institutions utilize multiple disciplines in forensic science to pursue their investigations and collectively provide a comprehensive analysis of the incident and its players. This presentation focused on the characteristics of the San Diego experience will address the issues of victim identification, evaluation of the cause of death, and investigating the circumstances of death leading to an opinion as to manner of death-natural, accident, suicide, homicide or undetermined. The character of the case defines its investigation. In some cases, the focus is on public health; in others, public safety. Forensic Sciences: Injury Causation: A Primer In the forensic sciences there are a number of questions asked in any medicolegal inquiry: Who, What, Where, When, How, By Whom, and Why. For the medical examiner/coroner the focus is on the requirements of the death certificate: identification, cause of death, and opinion as to manner of death. The latter is determined by the circumstances surrounding the injury and death. The medicolegal investigation is a series of phased inquiries beginning with incident reporting and fact acquisition, followed by analysis and interpretation, followed by conclusions, and if required recommendations. There often are several boards of inquiry on a particular incident depending on the nature of that incident: medical examiner/coroners inquiry/inquest, criminal investigation, safety investigation, etc each with different goals and objectives, rules of evidence, and SOPs. At the same time, there are concurrent autopsies: victims, vehicle (if appropriate), scene, physical evidence, and mission. Reconstruction of the events and the factors leading up to those events is dependent on the accuracy and relevance of those "independent" linked inquiries. Documentation of findings with sketches, diagrams, film, radiographs, and reports is critical. Linking those reports, or even knowing of their existence, is problematic, particularly if there are different jurisdictions. The medical inquiry, usually by the medical examiner/coroner, is structured based on the information available from the scene through personal attendance and/or investigators, police and EMS reports, if available, and information from witnesses and or family members. The latter is usually obtained during notification of next of kin or is volunteered or solicited during the investigation. The cause of death, a primary concern is related to injury causation. Injury causation has been approached by investigators in a number of modes: classification of traumatic or environmental injuries by cause, disease states by etiology, and human factors by behavior, disposition and opportunity. Examples of these follow: Classification of Trauma by Cause gun shot wounds sharp force injuries blast injuries radiation injuries blunt force injuries asphyxiation thermal injuries drowning injuries hyperthermia hypothermia chemical biological toxicological iatrogenic The vast majority of these traumatic injuries are from an applied force which has (1) magnitude-weight, velocity, (2) direction, (3) frequency, and (4) duration. Characterization of these qualities often assists in identifying the instrument or trauma biomechanics. Agents of injury are important in the analysis of trauma because the source of the force energy affects both the degree and distribution of that injury. The body's reaction to injury is what is observed by the clinician and pathologist, not the actual kinetic energy causing that presentation. It has come and gone. Common Surface Injuries Abrasion an injury to the surface of skin graze rough surface imprint localized pressure scratch a pointed object Avulsion tearing away of a part or tissue movement of a heavy object-a tire Blister fluid collection under the skin heat, skin diseases, infections, drugs, poisons, putrefaction Bruise hemorrhage into subcutaneous blunt force, blood tissues diseases Contusion injury to tissue without disruption blunt force Cut an incised wound, longer than deep sharp object Laceration crushing or tearing injury trauma Split longitudinal laceration of skin compression between bone and hard object or surface Stab penetrating wound, deeper than wide pointed object Classification of Disease by Etiology These are conditions that through examination and laboratory studies can be identified, diagnosed and usually understood as to progression based on the pathophysiology. They are generally approached by system systematically. Cardiac-acute myocardial infarct (AMI), coronary artery disease (CAD), atherosclerotic cardiovascular diseasee (ASCVD), arrhythmias (altered heart beats), myocarditis (infection of the heart muscles), cardiomyopathy, endocarditis or valvulopathy. Respiratory-pneumonia, pulmonary embolus, airway obstruction, poisoning, compression Neurological-CVA (stroke), encephalitis, meningitis, subdural/subarachnoid or epidural hemorrhages, paralysis, dementia, tumor Hepatic-cirrhosis, acute necrosis, hepatitis, tumor, other infiltrative process Renal-renal failure, sepsis, tumor, other infiltrative process, autoimmune Gastrointestinal-hemorrhage, obstruction, infection and peritonitis, tumor Lymphoreticular-immunocompromised, anemia, cytopenic, tumor, inflammation Endocrine-endocrinopathies-failure of pituitary, thyroid, parathyroids, adrenal glands, pancreas, sex organs (testes/ovaries) Musculoskeletal-tumors, infections, congenital defects, metabolic, inflammatory Cutaneous-infections, inflammatory, tumors, burns Aside from being the medical reason for an injury or response to an injury, these categories are usually evaluated relative to cause of death as incidental, contributory or proximal. In general, sudden death can only occur in three body systems: Nervous, Respiratory or Cardiovascular Systems. Understanding the pathophysiology is critical to understanding the medical condition and its stage or progression. Structure directs function and function influences structure. The strategic planning for litigation in cases involving impact trauma depends on the state of art in quantitative biophysical/biomechanical experiments and analysis of the minimum value of the injury causing force, its direction, and its velocity. The analysis follows Newton's principles of physics on the three laws of motion. First Law: If a force is exerted on a movable or moving object, it will change its state of motion. Second Law: If a force is exerted on an object, the object will move in the direction of applied force and, the more massive the object, the more force it takes to move it (F=ma). Third Law: If you exert a force on an object, the object exerts an equal and opposite force on you. Human Factors-Behavior, Disposition, Opportunity motivation education and training cognition anthropometry biomechanics speech and communication epidemiology-trends and patterns geography These categories are a mix of subjective and objective evaluations that color what is found and how it is interpreted. Intent may be assessed by actions or evidence of a preconceived plan. Cognition may be assessed by the victim's or perpetrator's understanding of the consequences of an action or reaction. Capability evaluations are based on the individual's training and education, possibly level of development. Standardized testing may be appropriate to determine level of development, understanding and motor skills. Opportunity, based on geography, time, anthropometrics, intent can be used for modus operandi considerations. Human factors analysis should be an important aspect of a number of medicolegal investigations. Studies have shown that in the majority of motor vehicle mishaps-automobiles, motorcycles, trucks, trains, buses and aircraft, human factors contribute as much as 70-80% of the risk factors. In such transportation mishaps particularly, the issue of survivability is raised. Was this a survivable accident? For the forensic scientist, pathologist, investigator, engineer, or lawyer, this can often be addressed by assessing three primary parameters: crash forces-both decelerative and impact, occupiable space, and post crash environment-especially fire and water. Pathologists, surgeons, and engineers are always looking to refine the biomarkers of trauma relative to magnitude and direction. What does it take to break this from this attitude (position, direction), for this duration (time)? Are the parameters measurable relative to intent? Are parameters experimentally determined in mathematical models, animal or human cadaver studies valid and applicable to living victims? There is almost always a safety component. Was the training and skill of the operator adequate? Was there a mechanical malfunction? Were there appropriate restraints? Were they used? Is there evidence of decreased capability based on medical conditions or toxicology studies? Did fatigue, dehydration, diabetes, exertion, hypothermia or hyperthermia play a role? In child abuse cases, the first indicator is usually an infant or child presenting to a clinic, hospital, school, social workers, law enforcement or morgue whose physical findings are not in keeping with a solicited history. The majority of these cases involves either suspected physical or sexual abuse, neglect or abandonment rather than mental abuse. There are a number of controversial areas in these cases such as the shaken baby syndrome, SIDS, infants or children with congenital or metabolic defects, eg. osteogenesis imperfecta, and biochemical abnormalities. Munchausen by Proxy is currently receiving a considerable amount of interest and is often quite difficult to prove in the absence of documented activities on the part of the parent or caretaker. Often these investigations are precipitated by a repeated event within a family that receives more scrutiny for one reason or another. In recent times, a similar effort has been directed at Elder Abuse, in part driven by an increasingly aged population and in part a different cultural perspective on "acceptable" conditions. In both cases, there are reasonably well understood risk factors and identifiable triggers. Both areas are often addressed by a multidisciplinary and usually multifactorial investigative effort recognized as a public health and safety concern. This author believes that both these areas of domestic violence require a similar or same level of medical documentation to include extensive imaging and behavioral/development assessments as well as medical and laboratory examinations. Forensic pathology usually involves the practice of autopsy pathology, microscopy and toxicology. There is significant reliance on other disciplines for additional data-forensic odontology (dentistry), forensic anthropology, forensic serology and molecular diagnostics (DNA profiling), criminalistics and forensic psychology and psychiatry. The "stitching" of these disciplines does not necessarily happen exclusively with or through the medical examiner or coroner. It often comes about either from law enforcement, the DA or defense teams particularly if there are unresolved temporal (when or where) or behavioral (why, how) issues. Lethality: Not all fatal injuries are immediately fatal. There is usually a survival or agonal period during which a victim and/or perpetrator can continue a course of action or initiate a course of action that might influence what is interpreted from the body, the scene evaluation and physical evidence. The time interval between injury and death continues to be a topic of discussion and laboratory inquiry. Laboratory evaluations are based on more precise understanding of the underlying pathophysiology. Defense Wounds: A defense wound is a term often applied to certain findings in trauma victims where the injury or injuries are attributed to defensive posturing on the part of the victim during the assault. These injuries are usually on the victim but can also be on the perpetrator. Fingernail scratches, bitemarks, punching or kicking injuries are examples of such injuries where wound character and location are both important. The term is most frequently is used in sharp force cases where elements of incising or slicing and stabbing are being sorted. It may equally be applied to certain gunshot wounds and patterned blunt force injuries. Time of Death: The estimation of the time of death in unwitnessed events ranges from minutes to seasons to years depending on what remains and in what condition. The longer the interval, the greater the variance in most cases. Bodies buried in soil fare better than those in water or remaining on the surface. In recent deaths, rigor mortis, livor mortis, calor mortis are the measured parameters most frequently used. Body temperature is still considered the most useful single indicator of the time of death during the first 15 hours. With decomposition which is a mix of putrefaction and autolysis there are substantial changes to the body including gas distention, discoloration, liquefaction, and disintegration. Occasionally the remains are more preserved than expected because of environmental conditions causing mummification or formation of adipocere. Environmental clues are frequently used to assist in PMI estimation including entomology, plant pathology, soil stratification, personal effects and cultural artifacts. Postmortem changes are of value to the pathologist because they: confirm the fact of death provide a rough indication of the time of death may indicate that the body has been moved after death may reflect the cause of death may be mistaken for pre-mortem lesions rapidly destroy signs of soft tissue injury and many features upon which identity is based In the ideal world fact and truth are synonymous. In reality, especially in the legal system, they are not necessarily the same. A fact is a circumstance, event or conclusion presumably based on the truth. It is the duty of the jury to determine the facts. Admissibility is a key determinant of facts offered for consideration and judgement. Key issues are fidelity, accuracy, and sincerity in searching for the facts and on faithfulness, exactness and probity in reporting the results of an investigation. Evidence is testimony, writings, material objects, and other things offered to prove the existence or nonexistence of a fact. Generally, there are three phases to a medicolegal investigation; (1) Why did the person die? (2) By what means and in what manner did death take place? And (3) Who was responsible? It is also generally accepted that three "bridges" are burnt behind the investigator: (1) movement of the body, (2) embalming of the body, and (3) disposition of the body-burial or cremation. Once the body is moved it cannot be exactly restored. This fact emphasizes the need for accurate documentation-identification, measurements, and photographs. 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