Injury pattern analysis: as a means of driver determination in a vehicular homicide: a case study.
Authors: Freeman, Michael D.
Nelson, Clifford
Pub Date: 03/22/2004
Publication: Name: The Forensic Examiner Publisher: American College of Forensic Examiners Audience: Professional Format: Magazine/Journal Subject: Health; Law; Science and technology Copyright: COPYRIGHT 2004 American College of Forensic Examiners ISSN: 1084-5569
Issue: Date: Spring, 2004 Source Volume: 13 Source Issue: 1
Accession Number: 114002668
Full Text: Abstract

Reconstruction of a fatal crash can be augmented, in certain circumstances, by information gleaned from the post-mortem evaluation. Further improvement of the scope and accuracy of an investigation can result from evaluation of the injuries of crash survivors, taking into account the conformity of individual vehicle interiors as well as the movement of the occupants during the crash.

We propose the term "Injury Pattern Analysis" (IPA) as a description of a fatal crash investigation technique that utilizes accident investigation and reconstruction techniques, occupant kinematics, post-mortem records, hospital and healthcare provider acute injury records, and other evidence as an adjunct to the investigation of homicides resulting from fatal crashes.

We present a detailed case study in IPA as an example of the practical application of the technique. It is recommended that medicolegal death investigators become familiar with the principles of IPA.

Keywords: Injury Pattern Analysis, motor vehicle crash, accident reconstruction, forensic pathology


Accident reconstruction is frequently relied upon by the medical examiner who is attempting to determine the mechanism of fatal injury following a motor vehicle crash. In some situations, however, the information gleaned from the post-mortem evaluation can provide key information for the reconstruction of the crash, particularly the position of the occupants at the time of the crash. For example, certain injuries are more likely to occur in a driver rather than a passenger due to interaction with the steering wheel and the foot pedals (see Tables 1 and 2). Cutaneous injuries, such as dicing, indicate incisions from side window glass, and passive restraints can leave characteristic patterned abrasions and contusions as evidence of forceful contact (see Tables 2 and 3). The accident reconstructionist will typically not have the medical training necessary to accurately or fully interpret the fatal injuries, and the forensic pathologist may not have an adequate understanding of accident reconstruction principles/the circumstances of the crash to determine the events of the crash and how they may have caused the observed injuries. Thus, there exists a potential gap in the investigation of some fatal crashes.

The existence of this gap indicates that certain fatal motor vehicle crashes require investigation beyond the expertise of an accident reconstructionist; they require the input of forensically trained medical personnel to help match injury patterns with a vehicle environment for various seating positions. This special expertise is particularly necessary when the occupants are ejected in a fatal crash, and there is doubt as to which of the occupants was driving at the time of the crash. Another situation occurs when the surviving occupants are able to exit the vehicle prior to any witnesses arriving on the scene. It is a generally accepted maxim among experienced investigators of such crashes that the survivor(s) invariably claim the decedent was driving at the time of the crash.

Forensic evidence can be gathered from the vehicle (blood, tissue, and hair samples) that may help place an occupant in the vehicle, but in many cases the vehicle is not readily available for evaluation, as the expense of keeping it in storage at a wrecking yard is typically borne by the law enforcement agency investigating the death (when the agency does not have such facilities available in-house).

Crash-related injuries vary with the type of crash and vehicles involved; restraint presence, use, and deployment characteristics; and the anthropometry and position of the vehicle occupants. For this reason, individual crashes have the potential to produce unique injury patterns evident in both the post-mortem evaluation of the decedent and in the physical evaluation of the surviving occupants. The investigation of injury patterns generated by unique crash scenarios and vehicle interiors is termed "Injury Pattern Analysis," or IPA, for the present discussion. Essential elements of an IPA are as follows:

* A detailed reconstruction of the crash, allowing for a determination of the principal direction of force of the crash if there was a collision, or, if the vehicle rolled, the manner in which it rolled;

* An understanding of occupant kinematics, based primarily on Newton's first law of motion governing the characteristics of inertia (a body in motion tends to stay in motion unless acted upon by an unbalanced force; a body at rest tends to stay at rest unless acted upon by an unbalanced force);

* An understanding of the presence, type, and performance of restraints present in the vehicle; if there are airbags and whether and when they deployed relative to the crash sequence;

* A detailed report of the post mortem evaluation; and

* Hospital admission records or first health care provider records detailing the acute injuries of the crash survivors.

Other variables to consider in some investigations are:

* Forensic evidence of vehicle interior contact, such as blood, tissue, or hair;

* Signs of strain in shoulder/lap restraints, if used;

* Signs of vehicle interior contact/mechanism of injury in occupant clothing; and

* The individual anthropometry of occupants and their seating positions.

The certainty with which the IPA identifies the occupant in a particular position in the vehicle can be translated into a forensic opinion graded by the strength of the evidence as a reasonable possibility, probability, or certainty.

In the following case study, we describe the utilization of IPA in providing a methodologic basis for the determination of the driver in a single vehicle fatal collision.

Case Study

On the evening of April 3, 1999, four intoxicated (>0.20 BAC in all) occupants of a 1984 Chevrolet Blazer were traveling on a straight section of a two-lane rural highway. They had been consuming alcoholic beverages since noon that day and had traded driving duties throughout the day, although RF had done most of the driving. There is undisputed and corroborated testimony that at approximately 9:00 p.m. the owner of the vehicle, DK, was seated in the rear seat on the driver's side of the vehicle next to JM, the brother of CM, one of the front-seat occupants. RF, the eventual defendant, was also seated in the front seat, and had admittedly been driving earlier in the evening. All occupants were unrestrained with the possible exception of RF, who later stated that he did not remember if he was restrained, but that he normally wore his seatbelt.

While traveling in excess of 85 mph, the right tires of the vehicle were driven off the side of the road. The driver over-corrected, bringing the vehicle back onto the roadway, causing the vehicle to yaw (slide sideways), rotating counterclockwise. The vehicle exited the left side of the road, passenger side first, and slid into a low ditch. The vehicle was tripped into a roll by the ditch, and continued to roll two-and-a-quarter times, coming to rest passenger side down. During the first full roll, the back section of the Blazer roof (made of fiberglass) separated from the rest of the vehicle, allowing the two rear-seat occupants to be ejected. DK, the rear driver's-side occupant, sustained a fatal head injury when the tailgate of the Blazer rolled over his head, the post-mortem examination revealed a coronally oriented basilar (hinge) fracture with accompanying subdural and subarachnoid hemorrhage.

The other rear-seat passenger was life-flighted to a Level 1 Trauma Center. State patrol officers arrived at the scene within 30 minutes and located one of the front-seat occupants, CM, standing near the vehicle. He stated that he had been in the front passenger scat at the time of the crash and that RF had been driving. CM stated that he had not been wearing a seat belt, and had been ejected from the vehicle. Upon closer questioning concerning his role in the crash, CM declined to comment further without an attorney present. CM was subsequently transported by ambulance to a nearby hospital for evaluation of contusions, abrasions, and a left scalp laceration.

Approximately one hour after the crash, RF arrived on the scene, wandering toward the site of the wreck through an adjacent field. Upon questioning, he claimed no memory of the crash, and was found to have a contusion on the right side of his head. He did not know how he had exited the vehicle. RF complained of right shoulder pain, and evaluation by Emergency Medical Service (EMS) personnel revealed a 15 cm vertical laceration of his right shin. The jeans covering the laceration were not torn. RF was also transported by ambulance to a local hospital for evaluation and treatment of his injuries.

The day following the crash, RF was questioned by a state trooper, at which time be admitted that he had been driving during the day of the crash, but could not recall who was driving at the time of the wreck. When asked if he was wearing a seat belt at the time of the crash, RF stated that he usually used a seat belt but could not recall whether he was using it at the time of the crash.

An accident reconstruction performed by the state police indicated that the vehicle was traveling approximately 74 mph when it left the roadway and began to roll. The reconstructionist evaluated hospital admission records of RF's injuries and determined that they did not specifically place him in either the driver or passenger seat. The reconstruction assumed that RF was ejected. On the strength of CM's testimony, RF was charged with vehicular manslaughter, with a potential penalty of a 192-month (16 years) incarceration.

Injury Pattern Analysis

An IPA was undertaken by the primary author, Dr. Freeman, to help determine the identity of the driver at the time of the crash. Thus, the IPA concerned only the front-seat passengers (CM and RF). The first step in the IPA was to obtain and review the EMS and hospital admitting records for RF and CM to determine the nature and distribution of their crash-related injuries. The results of this initial step are tabulated in Table 1 and are plotted in Diagrams 1 and 2. The two diagrams are reproductions of demonstrative exhibits used at trial.

Photographs were obtained of RF's right shoulder abrasion and right shin laceration that were taken shortly after the crash (see Illustrations 1 and 2). The second step of the IPA was to determine the movements of the occupants based on the reconstruction of the crash. With a rollover crash (rolling toward the driver's side or the passenger's side), an unrestrained driver can come into contact with the steering wheel, the driver's-side B-pillar (the structural support behind the driver's door), the driver's door, and the roof, resulting in chest, head, and left-sided blunt trauma injuries. Additionally, interaction with the brake or accelerator pedal can cause foot or ankle injuries. For an unrestrained passenger, most of the contact would be with the passenger door, the B-pillar, and the roof. For restrained occupants, abrasions and bruising from the shoulder and lap belts are expected. Ejection of either or both occupants can result in linear lacerations and abrasions, parallel with the path of ejection from the vehicle.


The third step of the IPA was to examine the Chevrolet Blazer in order to match the occupant injuries to the vehicle interior, considering the range of possibilities of occupant movement during the rollover. The roof on the driver's side was significantly crushed, and the rear fiberglass section was missing from the vehicle. An examination of the passenger's shoulder restraint revealed signs of strain at the D-ring attached to the B-pillar at the shoulder belt guide (note: the D-ring is pulled away from the plastic bracket cover in Illustration 3). The matching D-ring on the driver's side was undamaged, and a comparison with an exemplar vehicle of the same vehicle model and year revealed no such deformity (see Illustration 4).


Because this finding suggested substantial forceful loading of the passenger seatbelt in the crash under investigation, it was essential to rule out shoulder belt loading related to some unknown prior collision as a cause of the shoulder belt guide deformation. To this end, the vehicle was evaluated for evidence of front-end damage or repair that was unrelated to the crash in question. No evidence of front-end damage was found, and the previous owner was contacted and reported that the vehicle had not been involved in a prior front-impact collision or rollover (the two crash scenarios in which significant occupant loading of the shoulder restraint would be expected).

A potential cause of RF's right shin laceration was investigated within the vehicle interior. The top of the laceration was 17.5 inches above the bottom of the heel of the work boots worn at the time of the crash (see arrow in Illustration 2). A row of extruded hex-head screws below the glove box on the passenger side was found at a point 18 inches above the floorboard. The only pointed protrusion on the driver's side that could have caused the laceration was 11 inches above the floorboard between the brake and gas pedal and 7 inches above the base of the brake pedal.

No signs of blood, tissue, or hair were detected in the vehicle interior, but none were necessarily expected because the vehicle had been stored outside in harsh winter conditions without an intact roof structure for nearly one year prior to the inspection.

The final step in the IPA was to match the injuries to the vehicle interior to determine the place of the occupants in the vehicle as a reasonable possibility, probability, or certainty. This final step of the analysis is represented in Table 2 for RF and in Table 3 for CM.

RF's Injuries

The suboccipital contusion was considered to be most probably associated with a head strike against the shoulder belt guide on the passenger-side B-pillar, as with a rollover crash this part of the head would be relatively protected against contact with the roof. The right-shoulder abrasion matched the width of the shoulder restraint and closely matched the area of the shoulder that the restraint contacted in an exemplar vehicle (see Illustration 5). Additionally, the deepest point of the abrasion was at the apex of the supraclavicular fossa, which would be consistent with maximal loading of the belt when the vehicle was on its roof. While suggestive of contact with the passenger door, the right-hand contusion could also have occurred as the result of, or following, an ejection, and was therefore of indeterminate assistance in the IPA. The right costal margin contusion could have been caused by passenger door impact or driver's-side shoulder belt contact, or it could have resulted from an ejection, and thus was also categorized as indeterminate.


The right anterior superior iliac spine contusion was suggestive of the use of a lap belt in either the passenger or driver position; however, the presence of a right-shoulder injury pattern and the absence of any driver's side restraint marks indicated the use of the passenger restraint.

The right-thigh contusion could have resulted from contact with the door pull handle, but also could have been an ejection or post-ejection injury. It was concluded that the shin laceration could not have resulted from contact on the driver's side, because the superior margin of the wound projected 6.5 inches above the highest protrusion under the driver's-side dashboard. The injury did, however, match well with the projections found in the passenger-side interior (the hex-head screws). It is also unlikely that the laceration occurred during an ejection, as RF's denim jeans were intact over the laceration, indicating that it began inferiorly, and the jeans were able to "ride up" the shin while the laceration occurred. If the laceration had occurred during an ejection, it most likely would have started superiorly, and there would have been a resultant tear in the jeans.

CM's Injuries

As was the case with RF, the left suboccipital contusion was helpful for occupant placement, in that CM's injury lined up with the shoulder belt guide on the driver's-side B-pillar and was not consistent with a passenger position. The left frontal abrasion could have occurred during an ejection and was thus categorized as indeterminate. The midsternum contusion was considered a good match for the steering wheel, as was the right proximal ulnar contusion. The right lower quadrant abdominal contusion could have been associated with passenger-door contact, steering wheel contact, or ejection, and was considered indeterminate. The left foot and toe contusions were considered a relatively strong indicator that CM was in the driver's seat, as there is little opportunity for injury to the dorsum of the foot in a crash unless it is trapped beneath a foot pedal, most likely the brake. A volar foot or toe injury would be unlikely in an occupant wearing shoes.

Results of IPA Investigation

The strongest evidence for occupant position was found for RF, particularly the right-shoulder injury and the right-shin laceration. In a restrained occupant, these injuries could only have occurred in an occupant in the passenger seat. The abrasion over the right shoulder could only have resulted from sustained contact with a conforming structure, an unlikely occurrence in an unrestrained--and thus constantly moving-occupant in a rollover.

The evidence of the deformed D-ring, in combination with the evidence that there had been no prior crashes, indicated that it was highly likely that the front-seat passenger was restrained during the rollover. CM denied using a restraint and claimed to have been ejected, and had no record of injuries consistent with the use of a shoulder and lap belt. Thus, the evidence of the deformed shoulder-belt guide contradicted CM's claim that he was ejected from the passenger seat.

RF's injuries were not consistent with those of an unrestrained driver. All of the factors taken together indicated that, as a reasonable certainty, RF was in the front passenger seat at the time of the crash. It was determined that the IPA could place CM in the driver's seat as a reasonable probability, but the determination of RF as the passenger allowed for the deductive conclusion that CM was the driver as a reasonable certainty.

Testimony regarding occupant placement according to the IPA investigation was given in RF's trial as the sole theory of the defense. After less than 30 minutes of deliberation, the jury returned a verdict of not guilty.


In selected motor vehicle crash fatality cases, IPA can serve as a helpful adjunct to accident reconstruction and postwriteri-mortem investigations in reconstructing the event, with a particular benefit in the area of determining occupant placement at the time of the crash. It is necessary for the investigator performing the IPA to have a good understanding of accident reconstruction fundamentals, occupant kinematics, and the pathology of motor vehicle crash-induced trauma. Jurisdictions in which motor vehicle crash-related fatalities are common would benefit from the addition of IPA investigation resources.

This article is approved by the following for continuing education credit:

ACFEI provides this continuing education credit for Diplomates after June 2001 who are required to obtain 15 credits per year to maintain their status.

ACFEI provides this continuing education credit for Certified Medical Investigators who are required to obtain 15 credits per year to maintain their status.


DiMaio, D.J., & DiMaio V.J.M. (1989). Deaths due to motor vehicles. Forensic Pathology, 253-84.

Kulowski J. (1960). Crash injuries: The integrated medical aspects of automobile injuries and deaths. Springfield, IL: Charles C. Thomas.

Knight B. (1996). Transportation injuries. Forensic Pathology (2nd ed., pp. 275-94). London: Arnold.

Spitz, W.U. (1993). The road traffic victim. Medicolegal Investigation of Death (3rd ed., pp. 528-66). Springfield, IL: Charles C. Thomas.

About the Authors

Dr. Michael Freeman is a Fellow in the American College of Forensic Examiners Institute, and is a Diplomate of the American Board of Forensic Examiners and the American Board of Forensic Medicine. He serves as a clinical assistant professor at Oregon Health Sciences University School of Medicine, Department of Public Health and Preventive Medicine as a trauma epidemiologist. He serves as a Deputy Medical Examiner for Marion County and a Consultant Forensic Trauma Epidemiologist to the Medical Examiner Division, Oregon State Police, analyzing fatal collisions and the resulting injuries. Dr. Freeman holds a Ph.D. in trauma epidemiology and a master's of public health degree in biostatistics from Oregon State University. He has authored numerous publications on research into crash-related trauma and holds several editorial positions. Dr. Freeman's current vitae can be accessed on the web at

Dr. Clifford Nelson completed his medical degree and pathology residency training at Oregon Health Sciences University, and his forensic pathology fellowship at the Fulton County Medical Examiner's Office in Atlanta, Georgia. He is currently an Oregon Deputy State Medical Examiner working in the Portland office, and serves as the forensic pathologist of the coroner's offices of Cowlitz County and Pacific County, Washington. He is a member of the Disaster Mortuary Operation Response Team, and has served as an invited Faculty member for the New England Seminars in Forensic Sciences at Colby College, and as an instructor in the childproof course at the National Advocacy Center of the National District Attorneys' Association in South Carolina.
Table 1: Injuries to RF and CM

  RF's Injuries                      CM's Injuries

* Right suboccipital contusion     * Left suboccipital contusion
* Right shoulder abrasion          * Left frontal abrasion
* Right acromioclavicular sprain   * Midsternum contusion
* Right hand contusion             * Right proximal ulnar forearm
* Right anterior costal margin       contusion
  contusion                        * Right lower quadrant contusion
* Right anterior superior iliac    * Left foot and toe contusion
  spine contusion
* Right proximal lateral thigh
* Right anterior shin laceration

Table 2: Injury Pattern Analysis of RF's Injuries *

Injury                           Driver   Passenger   Indeterminate

Right suboccipital contusion                  X

Right shoulder abrasion and                   X
acromioclavicular sprain

Right hand contusion                                        X

Right anterior costal margin                                X

Right anterior superior iliac                 X
spine contusion

Right proximal lateral thigh                                X

Right anterior shin laceration                X

* on a "more probable than not" criterion

Table 3: Injury Pattern Analysis of CM's Injuries *

Injury                           Driver   Passenger   Indeterminate

Left suboccipital contusion         X

Left frontal abrasion                                       X

Midsternum contusion                X

Right proximal ulnar forearm        X

Right lower quadrant contusion                              X

Left foot and toe contusion         X

* on a "more probable than not" criterion
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