Forensic Medical Investigation of Motor Vehicle Incidents

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Decision errors may be catastrophic if the situation involves driving across roads with high traffic volumes and speeds. Elderly drivers are particularly at risk because of their decreased reaction times and potential problems with depth perception.

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A recent approach to the issue of human error is to view such errors as a symptom of system failure, and the premise that systems are not inherently safe. Vehicle speed and risk of a severe crash. Epidemiology ; — Factors affecting the severity of motor vehicle crashes involving elderly drivers in Ontario. The independent contribution of driver, crash, and vehicle characteristics to driver fatalities.

Are mobile speed cameras effective? A controlled before and after study. Injury Prevention ; — The relative effectiveness of a hidden versus visible speed camera program. Diamantopoulou K, Cameron M. An evaluation of the effectiveness of overt and covert speed enforcement achieved through mobile radar operations. Report No. The Illinois. An evaluation. Journal of Safety Research ; — Driver risk factors for sleeprelated crashes.

Driver distraction: a review of the literature. Living dangerously: driver distraction at high speed. Traffic Injury Prevention ; —7. Wireless telephones and the risk of road crashes. The effect of cellphone type on drivers subjective workload during concurrent driving and conversing.

Effect of cellular telephone conversations and other potential interference on reaction time in a braking response.

Forensic medical investigation of motor vehicle incidents — Monash University

Using mobile telephones: cognitive work load and attention resource allocation. Looked-but-failed-to-see-errors in traffic. Looking and failing to see error. The cost of experience? School of Cognitive and Computing Sciences. Prevalence and characteristics of red light running crashes in the United States. Analysis of motor-vehicle crashes at stop signs in four U.

Martinez R. Testimony to House Transportation and Infrastructure Committee. Surface Transportation Subcommittee; July 17, Hemmingway D, Solnick SJ. Fuzzy dice, dream cars, and indecent gestures: correlates of driver behaviour? An exploratory study of the relationship between road rage and crash experience in a representative sample of US drivers. Drivers judgements of safe distances in vehicle following. Low cost methods for improving traffic operations on two lane roads.

Close-following drivers on two-lane highways. Hakamies-Blomqvist L, Wahlstrom B. Why do older drivers give up driving? Warshawsky-Levne L, Shinar D. Effects of uncertainty, transmission type, driver age and gender on brake reaction and movement time. Journal of Safety Research ; 33 1 Age and fatality risk from similar severity impacts. Journal of Traffic Medicine ; — Characteristics of traffic crashes in Maryland — : differences among the youngest drivers.

Rationale for graduated licensing and the risks it should address. Injury Prevention ; 8:ii9—ii Carrying passengers as a risk factor for crashes fatal to 16 and 17 year old drivers. Journal of the American Medical Association ; — Williams AF. The compelling case for graduated licencing. Journal of Safety Research ; —4. Changes in collision rates amongst novice drivers during the first month of driving. Studying cognitive systems in context. Human Factors ; —7. Dekker SWA. Reconstructing human contributions to accidents: the new view on error and performance.

Additional Reading Brown ID. Driver fatigue. Evans L The dominant role of driver behaviour in traffic safety. American Journal of Public Health ; — Hedlund J, Compton R. Graduated driver licensing research in and beyond. A factor personality test for predicting automobile accidents of young drivers. Sleep related vehicle accidents. Does increased confidence among novice drivers imply a decrease in safety? The effects of skid training on slippery road accidents. Accident and Analysis Prevention ; — Overall injury risk to different drivers: combining exposure, frequency and severity models.

Young novice drivers: careless or clueless? Antecedents of fatigue, close calls, and crashes among commercial motor-vehicle drivers. Petridou E, Moustaki M. Human factors in the causation of road traffic crashes. European Journal of Epidemiology ; — Predicting red-light running behaviour: a traffic study in three urban settings.

Journal of Safety Research ; —8. Effects of red light cameras on violations and crashes: a review of the international literature. Shinar D, Compton R. Aggressive driving: an observational study of driver, vehicle, and situational variables. The effect of change in velocity on the development of medical complications in patients with multisystem trauma sustained in vehicular crashes. Establishing a benchmark of safety on Melbourne roads during A study in Arizona identified , collisions over a 6-year period of which were related to all medical conditions.

The circumstances and witness accounts may support the premise of driver incapacitation prior to a collision. The driver may have been seen to slump in the seat prior to the collision or the motor vehicle may have veered off the roadway onto the curb or into another motor vehicle with no attempt to correct the path or speed of the car. In cases in which a driver survives the motor vehicle collision and the overall circumstances suggest the possibility of underlying natural disease contributing to the incident, medical investigations performed in the hospital can document the presence of relevant natural disease.

In cases in which the driver dies following the motor vehicle incident, a postmortem examination will document the presence and severity of the underlying natural disease. The absence of any significant injury that would reasonably lead to death may enable the forensic pathologist to conclude the death occurred as a consequence of natural disease. In most cases, the presence of natural disease is coincidental to the cause of the motor vehicle incident.

The booklet serves as a guide for health professionals who provide medical support and opinions on drivers referred by the DLA. The guidelines for commercial vehicles are more stringent than for private drivers, reflecting their increased time on the road carrying large numbers of passengers, and controlling large and potentially dangerous vehicles.

In Australia, health professionals should be aware of privacy legislation applicable in their jurisdiction. Indemnity under transport law is provided for general practitioners who notify the DLA of patients with serious illnesses who have ignored repeated advice to stop driving because of serious illness and are a significant hazard to other road users.

The regulatory requirement for driver testing varies between the various states and territories in Australia. For example, in the State of Victoria, there is no requirement for medical assessment for a prescribed age, whereas in the State of Tasmania a medical assessment is required yearly from 75 years of age.

In the State of New South Wales, a medical assessment is required at 80 years of age and annually thereafter. Medical Conditions A comprehensive literature review on the influence of chronic disease on crash involvement of motor vehicle drivers was recently published by the Monash University Accident Research Centre. The Monash University Accident Research Centre review identified eight medical issues that were deemed high risk for a motor vehicle collision: alcohol abuse and dependence, dementia, epilepsy, multiple sclerosis, psychiatric disorders, sleep apnea and cataracts.

The following review of medical conditions will address medical diseases that can result in sudden incapacitation of a driver at the wheel of a motor vehicle.

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Low blood pressure is most commonly caused by an abnormality in heart rhythm, which in turn has a number of underlying causes. Ischaemic heart disease is the most common cause of death in developed countries Figure 3. Ischaemic heart disease refers to a relative deficiency of blood flow to the myocardium from stenosis of one or more coronary arteries. Coronary artery atherosclerosis is primarily a disease of older individuals, but is not uncommon in males in their third and fourth decades and may occasionally be seen in younger individuals with underlying disorders such as familial hypercholesterolaemia.

An acute complication of a coronary artery plaque such as coronary thrombosis or haemorrhage into the plaque may be associated with the sudden development of an abnormality in cardiac rhythm resulting in sudden collapse. Furthermore, the presence of myocardial fibrosis is associated with cardiac arrhythmias. Medications to treat ischaemic chest pain, especially in the early stages of the commencement of therapy, can also result in an abrupt fall in blood pressure.

Figure 3. In drivers who survive a motor vehicle collision and in whom there is suspicion of an acute ischaemic episode contributing to the collision, the clinical investigations including serum troponin levels and serial electrocardiographs may suggest a cardiac event around the time of the incident.

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However, blood loss or hypoxia arising from injuries sustained in the collision could precipitate a heart attack at the scene or shortly thereafter. The treating physician may be able to arrive at a reasonable conclusion as to the probability of the heart attack occurring before or after the collision, although in some instances no determination is possible. In Australia, it is recommended that the minimum nondriving period for private vehicle drivers following an established acute myocardial infarction is 2 weeks.

The recommended minimum nondriving period for commercial vehicle drivers is 3 months. It is important to note that the presence of cardiac disease does not usually necessitate a reduction or cessation of driving. A population of 97 patients with severe coronary artery disease who underwent cardiac surgery was investigated with respect to their driving habits before and after the procedure. Hypertensive heart disease is manifested as left ventricular hypertrophy in individuals with arterial hypertension.

Myocarditis is defined as inflammation of the heart muscle. In rare cases, an individual with myocarditis will suffer a sudden cardiac arrhythmia secondary to the electrical instability in the heart caused by the inflammatory process. Myocarditis is typically caused by a primary viral infection, or secondary to an autoimmune disease process. The autoimmune disease may be viral induced or part of a systemic autoimmune disease process. Rarely myocardial inflammation may occur in drug-induced eosinophillic myocarditis, and in conditions of uncertain aetiology such as giant cell myocarditis and sarcoidosis.

Aortic Dissection. Aortic dissection may rupture into the chest cavity, resulting in rapid exsanguination or dissect back to the pericardial sac causing cardiac tamponade. The typical case has aortic root dilatation, heart valve abnormalities and dysfunction, disproportionate growth of long bones, and lens dislocation. A cardiomyopathy is a disease of the myocardium that may be inherited, postinflammatory myocarditis , or secondary to an identifiable factor such as long-term alcohol abuse. Cardiomyopathies may cause sudden collapse or death as a result of a cardiac arrhythmia Figure 3.

Well recognised and described cardiomyopathies include hypertrophic cardiomyopathy, dilated cardiomyopathy, and arrhythmogenic right ventricular dysplasia. Microscopic examination showed classical branching of myofibres. Severe aortic stenosis that causes a significant pressure gradient across the valve is associated with a small risk of syncope and sudden death. Mitral valve prolapse is relatively common in the community and is usually asymptomatic. It may rarely be associated with sudden cardiac arrhythmias. Symptomatic coronary artery abnormalities are rare. Coronary artery bridging may cause a variety of clinical problems including angina pectoris, acute myocardial infarction, and life-threatening cardiac arrhythmias and sudden death.

Nervous System Disease processes affecting the central nervous system can lead to sudden and severe clinical symptoms or rapid death. Epilepsy Epilepsy is a medical condition characterised by seizures. Epilepsy is usually idiopathic but may be caused by pathologic processes associated with gliosis of the cerebral cortex. Secondary epilepsy may result from old head trauma, remote central nervous system infection, haemorrhage from vascular malformations, prior stroke, or tumours Figure 3. Examination of the brain in an individual with epilepsy is usually unremarkable.

Mesial temporal sclerosis, a gliotic thickening, or scarring of the hippocampus results from the effects of epileptiform seizures rather than being the underlying cause. The diagnosis of epilepsy results in restriction of driving based on medical fitness to drive. Granting of a licence generally requires a seizure free interval, the duration of which varies in different jurisdictions.

In the State of Victoria, Australia, a seizure-free interval of 3 to 6 months is required. In Canada in an invitational symposium comprising various medical experts recommended a seizure free interval of 6 to 12 months before driving was resumed. Furthermore, other studies of drivers with epilepsy have documented important individual features such as the type of seizure activity, consistent presence of an aura and the medical management of the disorder. A case-by-case approach is indicated with a review process combining both forensic and neurologic opinions.

Stroke A cerebrovascular accident stroke most commonly occurs as a complication of hypertension, cerebrovascular disease, or rupture of a berry aneurysm. The clinical manifestations of the stroke are determined by the site of the central nervous system involved, the underlying pathology, and the severity of the insult. Intracranial Haemorrhage. Intracranial haemorrhage occurs most commonly as a complication of hypertension or rupture of a berry aneurysm, and rarely from bleeding vascular lesions, tumours and coagulation disorders. Hypertensive intracerebral haemorrhage typically involves the basal ganglia and thalamus within the cerebral hemispheres, the pons, and the cerebellar hemispheres Figure 3.

Because the precise anatomic location of pathology within the brain is associated with specific neurologic deficits, one can predict the clinical consequences of haemorrhage into a particular region of the brain. The degree of neurologic deficit also depends on the size and rapidity of the haemorrhage. Haemorrhage overlying the base of the brain is usually the result of rupture of a berry aneurysm within the circle of Willis Figure 3. A berry aneurysm results from a congenital weakness within the wall of the artery, which occurs Figure 3. Rupture of the aneurysm causes a large amount of bleeding around the brain within the subarachnoid space and sometimes into the ventricular system.

This characteristically causes sudden onset of severe headache and may also cause rapid change in conscious state. Investigations in Intracranial Haemorrhage. A trauma victim who presents to hospital with central nervous system pathology will undergo diagnostic procedures, which may include multislice computed tomography scanning, magnetic resonance imaging, and angiography. The postmortem examination on an individual who dies as a consequence of a motor vehicle incident and who has underlying central nervous system pathology will have the pathologic processes identified and documented by neuropathologic examination.

The pathologist, neurologist, or neurosurgeon is often able to provide an opinion on the likelihood of the central nervous system haemorrhage being of natural or traumatic origin and the probability of the stroke contributing to the motor vehicle incident. Whilst the anatomic location may provide information on the likely neurologic deficit, clinical evaluation provides more reliable information on functional abilities. Driving After Stroke. Depending on the particular jurisdiction, it has been recommended that an individual who has suffered a stroke should not drive for at least 1 month after the event and 3 months after a subarachnoid haemorrhage.

Review by an appropriate specialist with regard to problems of visual field deficits, hemiplegia, and sensory neglect is important Figure 3. Elderly drivers have an increased risk of being involved in a motor vehicle incident with respect to all age groups except for men younger than 25 years of age. However, it is important to recognize that most older drivers are safe on road. The ability to drive a motor vehicle affords important mobility and independence for older members of the community. Elderly drivers are more likely to be involved in a collision at an intersection and to be involved in multiple vehicle incidents.

Elderly drivers are involved in collisions causing greater injury even after correcting for their less robust physical condition. A decrease in all three functions occurs with age. Laboratory tests have showed that individuals with Alzheimer's disease perform poorly on psychometric tests, with visual search studies predictive of driving impairment. However, a specific assessment of cognitive abilities identified those with an increased incidence of traffic violations. Driver simulator studies can measure cognitive and perception deficiencies.

A PC-based interactive driving simulator study by Lee and colleagues showed that individuals at increased risk of crashes could be identified using the driving simulator. In the State of Victoria, Australia, there is no compulsory system for testing older drivers. An individual may be reported to the appropriate authority by a concerned party, usually a police officer or medical practitioner.

A specialist medical assessment or driving review test may be required by the DLA. Because victims of CHI are often young individuals, it is important that they are able to regain mobility and independence as soon as is practical. Those with mild or moderate degrees of CHI usually resume driving without much difficulty.

Psychiatric Disorders The major psychiatric disorders of interest with respect to motor vehicle collisions are schizophrenia, depressive illness, and anxiety disorders. Psychiatric disorders are common in Western societies. Approximately one-quarter of all adult individuals will suffer a psychiatric illness during their lifetime.

Schizophrenia is a condition characterised by thought disorder, delusions, and hallucinations. The condition commonly affects relatively young men and women, and despite the use of psychotropic medications and support services, many affected individuals are marginalised in the community. Acute psychotic episodes with severe abnormalities in thought processes can lead to bizarre behaviour. Depressive illness is a mood disorder characterised by marked decrease in mood and affect, feelings of hopelessness, disturbance of sleep, and suicidal ideation.

Depressive illness may also be associated with psychotic episodes. Anxiety disorders are a varied group of psychiatric disorders characterised by excessive, inappropriate, and irrational anxiety that may be directed to specific situations. Chronic psychiatric disorders have potential detrimental affects on the process of driving because of problems with concentration, information processing, aggressive driving behaviour, and suicidal thoughts.

A study by Vernon and colleagues showed that drivers with psychiatric disorders have significantly higher rates of at fault crashes compared with controls. Suicide by motor vehicle undoubtedly occurs but can be difficult to prove. A series of patients undergoing psychiatric assessment expressed the desire to use a motor vehicle to commit suicide.

A literature review did not support the suggestion that insulin-dependent diabetic drivers have an increased risk of traffic collisions over nondiabetic drivers. On the other hand, older insulin-dependent drivers showed impaired judgement of hypoglycaemia. The Impact of Cataract on Mobility project showed that those patients who underwent cataract surgery and intraocular lens implantation had half the rate of collision involvement compared with matched controls.

Sleep apnea is a disorder characterised by multiple episodes of upper airway obstruction during sleep that leads to a cessation of breathing for about 10 or more seconds. The disorder is particularly common in obese, middle-age males. The disturbed sleep pattern may be associated with sleepiness during the daytime with short episodes of daytime sleep.

Studies have shown an increased risk of crashes in individuals diagnosed with sleep apnea. Seizure-related motor vehicle crashes in Arizona before and after reducing the driving restriction from 12 to 3 months. Mayo Clinic Proceedings ; — Gresset J, Meyer F. Risk of automotive accidents amongst elderly drivers with impairments or chronic diseases. Canadian Journal of Public Health ; — Assessing fitness to drive for commercial and private vehicle drivers. Vermont South: Austroads, Ar ticle available at www. Hocking B, Landgren F.

New medical standards for drivers. Australian Family Physician ; — Ahlgren E, Rutberg H.

Forensic Medical Investigation of Motor Vehicle Incidents

Patients with coronary artery disease are active car drivers both before and soon after heart surgery. Hypertensive heart disease. Hypertension Research ; — The Lancet ; — Maron BJ. Hypertrophic cardiomyopathy: a systematic review. The Journal of the American Medical Association ; — Arrhythmogenic right ventricular cardiomyopathy: clinical presentation, diagnosis, and management.

American Journal of Medicine ; — Twenty years of progress and beckoning frontiers in cardiovascular pathology. Cardiovascular Pathology ; — Bjerregaard P, Gussak I. Sort QT syndrome. Annals of Noninvasive Electrocardiology ; — Roberts R. Genomics and cardiac arrhythmias. Journal of the American College of Cardiologists ; — What is the Brugada syndrome?

Cardiology in Review ; — Mitral valve prolapse. Lancet ; — Baltaxe HA, Wixson D. The incidence of congenital abnormalities of the coronary arteries in the adult population. Radiology ; — Symptomatic myocardial bridges: overview of ischemic mechanisms and current diagnostic and treatment strategies.

Epilepsy and motor vehicle driving—a symposium held in Quebec City, November Canadian Journal of Neurological Sciences ; — Taylor JF, editor. Medical Aspects of Fitness to Drive. A Guide for Medical Practitioners. London: Medical Commission on Accident Prevention, Gastaut H, Zifkin BG. The risk of automobile accidents with seizures occurring while driving: relation to seizure type. Neurology ; — Concurrent validity of the stroke driver's screening assessment. Archive of Physical Medicine and Rehabilitation ; — Risk older drivers face themselves and threats they pose to other road users.

Internal Journal of Epidemiology ; — Hakamies-Blomqvist L. Aging and fatal accidents in male and female drivers. Journal of Gerontology ; S—S Motor vehicle crashes in dementia of the Alzheimer's type. Annals of Neurology ; —6. Halpern D. Age differences in response time to vehicle traffic signs. Experimental Aging Research ; — Larsson L. Aging in mammalian skeletal muscle. The Aging Motor System. New York: Praeger, ; pp 60— Driving and Alzheimer's disease: the risk of crashes.

Prevalence of Alzheimer's disease in a retirement community. American Journal of Epidemiology ; — Attention and driving performance in Alzheimer's disease. Journal of Gerontology: Psychological Sciences ; — Vehicle crash involvement and cognitive deficit in older drivers. Performance based measurements among elderly drivers and non-drivers. Journal of the American Geriatrics Society ; — Can a physician recognize an older driver with increased crash risk potential? Using a driver simulator to identify older drivers at inflated risk of motor vehicle crashes.

Di Stefano M, Macdonald W. Assessment of older drivers; relationships among on-road errors, medical conditions and test outcome. Journal of Safety Research ; — Fitness to drive after traumatic brain injury. Neuropsychological Rehabilitation ; — Evaluating the crash and citation rates of Utah drivers licensed with medical conditions, — Crashes among schizophrenic outpatients.

Comprehensive Psychiatry ; — Hamburger E. Risk of accidents in drivers with epilepsy. Journal of Neurology, Neurosurgery and Psychiatry ; — Insulin-treated diabetes and driving in the UK. Diabetic Medicine ; — MacLeod KM. Diabetes and driving: towards equitable, evidence-based decision-making. Diabetic Medicine ; 16 4 The perception of safe driving ability during hypoglycemia in patients with type 1 diabetes mellitus. Impact of cataract surgery on motor vehicle crash involvement by older adults.

Psychology of Aging ; — Visual attention problems as a predictor of vehicle crashes in older drivers. Investigative Ophthalmology and Visual Science ; — Accident Analysis and Prevention ; 35 3 — Severity of sleep apnea and automobile crashes correspondence. New England Journal of Medicine ; — Sleepiness-related accidents in sleep apnea patients.

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Sleep ; —7. Automobile accidents in patients with sleep apnea syndrome: an epidemiological and mechanistic study. The position of an abrasion on the skin surface indicates a site of the application of blunt force. The characteristics of the injury may provide information with respect to the direction of the impact force and occasionally information regarding the shape and nature of the object that caused the injury.

Following death from a traumatic event that resulted in abraded injuries, it is not uncommon for the affected skin surface to develop a tan-coloured leathery appearance Figure 4. This parchment effect is due to drying of the tissues and does not indicate the injuries were sustained postmortem. Subcutaneous dissection may demonstrate the presence of bruising, which confirms the injuries were sustained during life, although some parchmentlike abraded injuries that had clearly occurred in life do not show subcutaneous bruising.

Direction of Impact Skin tags can indicate the relative movement of an object and the skin. Skin tags are small, raised pieces of skin produced when an object moves across the skin surface and point toward differential blunt force contact. Thus if a broad metallic object impacted the lower limbs at the knee joint and travelled down the leg toward the foot, the skin tags produced from contact with the skin would tend to be located at the distal aspect of the abraded injuries. It is important to note that such injuries do not indicate which object was moving and which was stationary.

Surface and Nature of the Object Examination of an abrasion can provide information regarding the surface of the object that impacted with the skin surface. Scratches or linear abrasions are injuries to the skin that occur from contact with a fine point. Broad abraded injuries result from contact with a relatively wide surface.

Depending upon the nature of the object that abrades the skin, there may be foreign material derived from the object embedded or adherent to the surface of the skin. The most common materials associated with the skin of the pedestrian victim of a collision are flecks of paint, fine particles of glass, and grease. Shape of the Object Examination of the abrasion may provide information regarding the shape of the object that impacted with the skin surface. The majority of abraded injuries to the skin are nonspecific; however, some have distinct shapes called patterned, abraded injuries Figure 4.

An analogy is a stamp producing its image on a sheet of white paper. If the process is repeated with the paper placed on a firm and irregular surface, only portions of the stamp surface might be seen on the paper. Because the human body has numerous curves, is covered with various layers of clothing, and may come into contact with a small portion of a larger object, patterned injuries usually do not reproduce the complete mirror image of the object.

There may even be disagreement between observers as to whether an injury is patterned and whether a given patterned abraded is significant. The classic patterned abraded injury is the seat belt abrasion Figure 4.

Patterned abrasions are also caused from contact with objects within the vehicle cabin in occupants of motor vehicles. Peculiar shapes and patterns are becoming less common with improved restraint systems and vehicle designers producing rounded edges to instrument and door panels. Figure 4. These include grill components, headlight and windshield surrounds and wiper assemblies, and wheels.

The identification of a patterned, abraded injury in a pedestrian may aid in determining the pedestrian's position at impact. Abrasions from Indirect Forces Incidents involving extreme forces that cause marked deformation to the body may result in superficial stretch marks to the skin. These marks may develop anywhere in the body, but tend to occur in natural creases such as the groin and axillae. A common setting in which this injury is seen is in cases in which the torso is run over by a motor vehicle resulting in a fractured pelvis with wide separation of the pubic rami.

Stretch-type injuries may then be seen in the inguinal creases Figure 4. Lacerations Definition A laceration may be defined as an injury resulting from blunt force that results in tearing of the skin. A laceration usually has irregular margins with so-called skin bridges within the depths of the wound. Skin bridges are connective tissues, nerves, and blood vessels beneath the skin in subcutaneous tissue that extend across the opposing edges of the laceration Figure 4. Because lacerations are due Figure 4. Direction and Nature of the Impact A laceration indicates a site of the application of blunt force.

A tangential impact can result in undermining of the laceration in the direction of the force. Degloving-type lacerated injuries refer to extreme undermining with separation of the skin from the underlying deeper tissues. These injuries are especially prominent in runover incidents from the action of a rotating tire, but may also be seen in tangential impacts involving considerable force.

Bruises Definition A bruise may be defined as the extravasation of blood from the blood vessels into surrounding tissues. A bruise results from the application of blunt force.

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The haemorrhage may involve subcutaneous fat or deep soft tissues including muscle. Point of Impact The site of bruising to the skin surface does not always correlate with the point of impact. A fractured base of skull may lead to bruising behind the ears or bilateral periorbital hematomas.

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These bruises result from blood tracking between tissue planes from a distant point to the surface of the skin. Examination of a bruise to the surface of the skin does not allow a determination of the direction of the impact. In a postmortem examination, subcutaneous and deeper dissection may reveal varied degrees of bruising in sequentially deeper tissues with a directional component. In these circumstances, one may provide a guarded opinion as to the direction of force.

Macroscopic and microscopic examination of fatty tissue may shed light on the origin of a bruise. Bruising that occurs from blood tracking from a distant site will travel along tissue planes. Direct trauma of a mild degree results in perilobular haemorrhage. As the degree of force increases, there is additional intralobular haemorrhage and then rupture and destruction of supporting connective tissues, ultimately leading to a fluid-filled cavity.

For the same reason, the shape of the bruise is usually not well defined. Intradermal bruises may be viewed as analogous to a patterned abrasion, and the production of such patterned injuries is often due to a combination of abrasion of the skin and localised haemorrhage into the dermis Figure 4. Degree of Bruising The amount of bruising that occurs from impact by a particular object with a certain degree of force can vary considerably between different individuals.

The bruising produced does not necessarily reflect the degree of force in a particular incident. Bruising varies with extremes of age, the site of injury, and the presence of underlying medical conditions. Regions of the body with a rich vascular supply or abundant subcutaneous fatty tissue tend to develop a greater amount of bruising.

Facial trauma will tend to develop a greater degree of bruising than a chest injury of identical force. Disease processes such as bleeding disorders and severe chronic liver and kidney disease are examples of the many conditions that can lead to excess bruising. Several medical therapies, such as anticoagulant medications and corticosteroids, are associated with a bleeding tendency. Petechial haemorrhages are most commonly seen on skin and mucous membranes.

On the skin, they often involve periorbital and retroauricular skin. The mucosal surfaces often affected include the conjunctivae, sclera, and buccal mucosa. During an autopsy examination, petechiae may be visible over many organs. Petechial haemorrhages are nonspecific but classically seen in asphyxial deaths. Deaths from mechanical asphyxia usually have widespread and often confluent petechiae.

Incised and Stab Injuries Definition Incised and stab injuries may be defined as injuries that result from the application of sharp force. An incised injury is wider than it is deep whereas a stab injury is deeper than it is wide. Sharp force injuries differ from lacerations in that the edges are clean and well defined with no surrounding abrasions unless there is an associated blunt force injury. Compared with lacerations, there are no skin bridges as the sharp implement also divides the deeper connective tissues.

In motor vehicle incidents, sharp-force injuries may result from contact with glass and metal edges Figure 4. Contact from broken tempered glass from windows typically causes punctate, dicing, incised injuries. Ligaments are connective tissues that maintain the structural integrity of joints. A ligamentous tear may be partial or complete and lead to varying laxity of the joint. Fractures Bone is a highly specialised connective tissue that generally has an inner spongy trabecular region surrounded by dense cortical bone.

Long bones are composed of a central portion called the diaphysis, which expands toward its opposing ends at the metaphysis, and two opposing cartilage capped ends adjacent to joints called the epiphyses. Fractures may occur at any of these points. A fracture may extend transversely across the bone, spiral around the bone, or shatter into numerous fragments in comminuted fractures Figure 4.

A fracture may be closed or compound. Different mechanisms of injury tend to result in certain types of fracture. Rotational forces tend to cause spiral fractures, axial loads tend to cause compression fractures, and direct perpendicular forces tend to cause transverse fractures. Bone is stronger in compression than it is in tension. Thus when one considers an upright pedestrian in which a force is applied to the anterior aspect of the tibia, the fracture begins at the posterior aspect of the bone where the tensile forces are acting.

The fracture then extends to the anterior part of the bone that is under compression force. Ligament Injury Joints are complex structures that in varying degrees depend on ligaments and muscles to maintain anatomic and functional integrity. The importance Figure 4. Angulation of distal fractured portion of femur with displacement of bone fragment suggests impact from medial aspect of thigh. The ball-and-socket joint of the hip has far greater stability from its bony configuration than the rolling type joint of the knee.

Each different ligament around a particular joint prevents excessive movement in a particular direction. The lateral collateral ligament of the knee resists adduction of the joint. Severe force that leads to excessive adduction of the knee may result in a partial or complete tear of the lateral collateral ligament or avulsion of the ligament's attachment to bone Figure 4. Identification of ligament injuries may thus provide information regarding the direction of the application of force. Demonstration of Fractures and Ligament Injuries In the clinical setting and at postmortem radiographs, computed tomography scans and magnetic resonance imaging can demonstrate fractures and softtissue injury.

At the postmortem examination, conventional radiographs, computed tomography, and magnetic resonance imaging images provide a permanent objective record of the fracture that can be reviewed by interested parties at a later date Figures 4. Burns Burns in motor vehicle incidents occur most commonly when a fire results from a collision and an occupant is unable to extricate himself or herself from the vehicle. This may be due to injuries sustained in the incident, from the effects of natural disease, or from being trapped by parts of the vehicle.

Burns may be superficial or full thickness and involve the skin, soft tissues, bone, or airway. In addition, the seating position of a vehicle occupant determines his or her risk of injury. It has been shown that the rear seat position, and in children the centre rear seat position, carries a lower risk of injury and death compared with the front seat in motor vehicle crashes. Note the integrity of the vehicle cabin and deployed airbags. The design of vehicle safety features, in particular restraint systems and frontal crush zones, were largely developed to address the forces involved in frontal impacts.

Frontal collisions are common in rural locations. Driver drowsiness and inattention on two-lane highways may be a contributing factor when cars drift onto the wrong side of the road. Overtaking maneuvers are a further important issue in some cases of frontal collisions. Less commonly, an incident that occurred in the correct lane leads to the vehicle crossing onto the wrong side of the road, resulting in a frontal collision. Oblique Frontal Collisions Oblique frontal collisions OFCs are defined as collisions involving the left or right front quarters of a motor vehicle in which the impact is angled.

OFCs are more common in elderly drivers. OFCs occur most commonly when a vehicle is turning at an intersection and moves into the path of an oncoming vehicle. OFCs have a higher incidence of significant injury and death compared with true frontal collisions of a given severity and is partly related to increased cabin intrusion. Unrestrained Occupant Newton's First Law of Motion states that an object will continue at its velocity unless acted on by another force.

If one ignores the minor frictional forces that are present between the occupant and seat and floor, the major force that will alter the occupant's velocity is contact with interior components of the vehicle cabin. The Second Law states that force is equal to the mass of a body multiplied by its acceleration. From this equation, it is clear that the abrupt deceleration that occurs from the occupant's body impacting with the vehicle interior following a highspeed crash will lead to the application of considerable force.

The seat belt prevents rapid deceleration against the interior components of the vehicle cabin. Unrestrained drivers in frontal crashes impact with the steering wheel and assembly, the windshield and surrounds, instrument panel, and floor pan Figure 5. The major injury associated with direct impact is head injury.

Head impact tends to be frontal, leading to forced hyperextension of the upper cervical spine, and fracture dislocation of the atlanto-occipital joint is a common injury and cause of death Figure 5. Subsequent blunt force trauma leads to further chest, abdominal, pelvic, and upper and lower leg injuries. Figure 5. A common cervical spine injury is fractured odontoid process. Head Injury Head impact usually occurs from contact with the A-pillar, side of the vehicle roof, door frame, B-pillar and windows and surrounds, and, in the case of rollover, the vehicle roof and other occupants.

This brain injury is from rotational forces causing differential movement within different regions of the brain, leading to damage to nerve axons and small blood vessels. Subdural haemorrhage is classically caused by rotational forces acting on the head resulting in differential movement between the skull and relatively adherent dura, and brain leading to division of perforating small venous channels. Subdural haemorrhage is often associated with diffuse axonal injury. A subdural haemorrhage can accumulate rapidly to a volume 50 to mL , resulting in compression of the underlying brain.

Basal traumatic subarachnoid haemorrhage suggests rupture of the intracranial vertebral or basilar arteries or rupture of a vertebral artery within the cervical spine. An extradural haemorrhage is classically caused by rupture of the middle meningeal artery within the squamous temporal bone. It is uncommon for an isolated extradural haemorrhage to be the sole cause of death in a motor vehicle incident. The haemorrhage has to strip the densely adherent dura from the skull and form a collection such that the underlying brain is compressed and distorted. This usually takes some hours and provides enough time for surgical evacuation of the blood clot.

Extradural haemorrhage in a motor vehicle collision is usually associated with other significant forms of head injury. A cause of death in head injury that may have subtle changes at postmortem is a tear at the pontomedullary junction in the brainstem. Secondary Brain Injury Secondary brain injury is common and can be as important to the survival and functional recovery of a crash victim as the primary insult. Secondary brain injury refers to brain swelling and haemorrhage that occurs as a consequence of a number of factors including, but not limited to, hypoxia, hypotension, and coagulopathy.

Head injury is a recognised cause of apnea. Experimental evidence suggests the magnitude of the brain impact is directly proportional to the onset and persistence of apnea. In many cases secondary injury is inevitable because of the isolated location of the motor vehicle incident. Deceleration Injury The uncontrolled deceleration that occurs in unrestrained vehicle occupants, primarily but not exclusive to frontal collisions, can lead to rapidly fatal deceleration injuries to the cardiovascular system.

The typical deceleration injury that leads to death is transection of the descending thoracic aorta Figure 5. The injury classically occurs at the level of the isthmus. Tears may also occur in the ascending thoracic aorta and vascular branches from the arch. Rupture of an atrial appendage is a further significant traumatic injury.

Pulmonary haemorrhage of varying severity can occur secondary to deceleration. Avulsion of major thoracic and intra-abdominal viscera including the liver, kidneys, lungs, and heart from vascular attachments are further catastrophic injuries. Tracheobronchial disruption is a further deceleration injury, which may be seen in the absence of other significant chest injuries, and may be the sole cause of death.

The introduction of crush zones to the front of cars, seat belts with energy management systems and front airbags have been designed to lengthen the duration of deceleration and subsequently reduce deceleration injury. Restrained Occupant The motor vehicle occupant wearing a seat belt involved in a frontal collision will also move forward following frontal impact, although obviously to a far lesser degree than unrestrained occupants.

Vehicles fitted with seat belt pretensioners will have even less forward movement. Significant forces still apply to the upper cervical spine as a result of rapid movement of the victim's head. Vehicle intrusion is a further cause of blunt force injury. Direct impact between the knee and the dashboard is decreased in the restrained occupant. Floor pan intrusion is a major cause of lower limb injury Figure 5.

Restrained occupants in motor vehicle collisions most commonly die as a result of head injury or deceleration injury. Other significant injuries result from the injuries described below. Blunt Chest Trauma Chest injury from direct blunt trauma can lead directly to death, but more commonly contributes to death in association with other injuries. Massive pulmonary contusions, ruptured pulmonary vein, ruptured heart with pericardial tamponade, and widespread rib fractures sometimes associated with lung and cardiac lacerations are injuries seen with severe chest trauma.

The presence of fractures of the first and second ribs is indicative of severe blunt force to the chest, and should be a stimulus for investigation of other significant chest and abdominal injuries. Multiple fractured ribs or fractured sternum is a significant injury in the elderly and crash victims with other major medical conditions. In these subgroups, a fractured sternum or multiple fractured ribs especially with a flail segment, there is a high morbidity and mortality rate and often a requirement for a period of ventilation in an intensive care unit with appropriate pain management.

When death occurs, it is often the result of a combination of respiratory failure and bronchopneumonia. Tension pneumothorax is a medical emergency that can lead to rapid death. Radiolucent right chest from accumulation of air within the right pleural space and showing mediastinal shift to the left side. Hence the lungs and heart are increasingly compressed from the expanding volume of air, eventually leading to external compression of the heart and lungs with eventual cardiovascular collapse Figure 5.

The pressure can be relieved by the insertion of a cannula into the chest. Blunt Abdominal Trauma Blunt trauma to the abdomen can cause ruptures to abdominal viscera including the liver, spleen, bowel, and mesenteries leading to hemoperitoneum. Blunt trauma to the right side of the abdomen tends to cause liver damage, whereas trauma to the left side of the abdomen tends to cause splenic injury.

Young, previously healthy trauma victims may compensate for massive abdominal injury for a significant period before the onset of cardiovascular collapse. Abdominal trauma and haemorrhage from ruptured pelvic vessels secondary to a pelvic fracture can cause massive retroperitoneal haemorrhage. Traumatic acute pancreatitis is a relatively uncommon sequela of abdominal trauma. Pelvic and Lower Limb Trauma Pelvic fractures tend to occur along the direction of the application of force, though there are numerous exceptions to this general rule Figure 5.

Axial forces transmitted along the femur from a frontal impact may cause posterior dislocation of the hip joint. Posterior hip dislocation may occur from direct impact to the knee from the dashboard, though others have postulated the mechanism of injury usually results from hip flexion, adduction, and internal rotation as occurs when the driver presses hard on the brake pedal just prior to the impact. The length of a skid mark can often allow calculation of the original speed of a vehicle for example. Vehicle speeds are frequently underestimated by a driver, so an independent estimate of speed is often essential in collisions.

Inspection of the road surface is also vital, especially when traction has been lost due to black ice , diesel fuel contamination, or obstacles such as road debris. Data from an event data recorder also provides valuable information such as the speed of the vehicle a few seconds before the collision. As part of the investigation of a vehicle collision, an investigator typically documents evidence at the collision site and the damage to the vehicles.

The use of 3-dimensional laser scanning has become a common method for documentation. The product of scanning is a 3D point cloud that can be used to take measurements and create computer models used in the analysis of the collision. The 3D data can be incorporated into many of the computer simulation programs used in collision reconstruction. The 3D point clouds and models can also be used for creating visuals to illustrate the analysis and to show views of witnesses and the involved drivers.

The Bosch CDR Tool is a commercially available tool, allowing to image crash data directly from all supported vehicles giving a detailed report of critical data parameters leading up to and during a crash. Some of the parameters include pre-crash data, vehicle speed, brake status, throttle position, ignition cycles, delta-V, seat belt status, and others. Hyundai and Kia as well as most heavy commercial vehicles are equipped with EDR, however are not supported by Bosch equipment. To access this information a diagnostic retrieval tool unique to these manufacturers is required.

Vehicular collision reconstruction analysis includes processing data collecting, evaluating possible hypotheses, creating models, recreating collisions, testing, and utilizing software simulations. Like many other technical activities, collision reconstruction has been revolutionized by the use of powerful, inexpensive computers and specialty software. Various types of collision reconstruction software are used to recreate crash and crime scenes and to perform other useful tasks involved in reconstructing collisions.

Collision reconstruction software is regularly used by law enforcement personnel and consultants to analyze a collision and to demonstrate what occurred in a collision. Examples of types of software used by collision reconstructionists are CAD computer aided design programs, vehicle specification databases, momentum and energy analysis programs, collision simulators, and photogrammetry software.

After the analysis is completed, forensic engineers compile report findings, diagrams, and animations to form their expert testimony and conclusions relating to the collision. Forensic animation typically depicts all or part of a collision sequence in a video format so that non-technical parties, such as juries, can easily understand the expert's opinions regarding that event.

To be physically realistic, an animation needs to be created by someone with a knowledge of physics, dynamics and engineering. When animations are used in a courtroom setting, they should be carefully scrutinized. Animation software can be easily misused, because motions which are not physically possible can be displayed. A reliable animation must be based on physical evidence and calculations which embody the laws of physics, and the animation should only be used to demonstrate in a visual fashion the underlying calculations made by the expert analyzing the case.

Motorcycle collision reconstruction is similar to other collision reconstruction techniques and relies on the same basic principles of conservation of energy and momentum as automobile collision reconstruction plus adds the specifics of motorcycle dynamics and rider control. Proper reconstruction of a motorcycle collision requires detailed knowledge of motorcycle dynamics plus knowledge of how motorcycles react to rider input. Motorcycle collision reconstruction relies on knowledge of the five phases of a motorcycle collision. Perception—reaction: This is the phase where the rider perceives a collision hazard and decides on a response.

Physical evidence at the scene combined with statements from witnesses can give clues as to what type of avoidance occurred. If the front wheel locks, the rider will almost certainly lose control and crash. If the rider loses control and crashes while braking, the motorcycle and rider usually separate and slide in the same trajectory they were moving in before the crash. Damage caused by impact can be evaluated and combined with sliding distance to help determine the motorcycle's speed during the collision sequence.

Post-impact motion: After impact, additional movement to the point of final rest can occur. The rider frequently separates from the motorcycle and travels independently to the final point of rest. Analysis of post-impact travel distance can also determine speeds associated with the collision. Northwestern University Center for Public Safety conducts Traffic Crash Investigation courses utilized by both law enforcement and public agencies. Each team consists of inspectors with specialized training in traffic collision reconstruction, traffic engineering, automotive engineering, and vehicle dynamics.

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