O'Brian C. Smith

Identification of Traumatic Injury in Burned Cranial Bone: An Experimental Approach

Interpreting patterns of injury in victims of fire-related deaths poses challenges for forensic investigators. Determining manner of death (accident, suicide or homicide) using charred remains is compounded by the thermal distortion and fragmentation of soft and skeletal tissues. Heat degrades thin cranial structures and obscures the characteristic signatures of perimortem ballistic, blunt, and sharp force trauma in bone, making differentiation from thermal trauma difficult. This study documents the survivability and features of traumatic injury through all stages of burning for soft tissue reduction and organic degradation of cranial bone. Forty cadaver heads were burned in environments simulating forensic fires. Progression of thermal degradation was photographically documented throughout the destructive stages for soft tissues and bone to establish expected burn sequence patterns for the head. In addition to testing intact vaults, a percentage were selectively traumatized to introduce the variables of soft tissue disruption, fractures, impact marks, and incisions throughout the cremation process. Skeletal materials were recovered, reconstructed, and correlated with photographs to discern burn patterns and survivability of traumatic features. This study produced two important results: (1) Identification of preexistent trauma is possible in reconstructed burned cranial bone. Signatures of ballistic (internal and external bevel, secondary fractures), blunt force (impact site, radiating fractures), and sharp force (incisions, stabs, sectioning) survive the cremation process. (2) In non-traumatized specimens, the skull does not explode from steam pressure but does fragment as a result of external forces (collapsed debris, extinguishment methods) and handling. The features of both results are sequentially described throughout the progression of thermal destruction.

Cranial Fracture Patterns and Estimate of Direction from Low Velocity Gunshot Wounds

Cranial trauma produced by low velocity gunshot wounds is investigated in an autopsy series. In skeletonized remains with postmortem damage, or after surgical debridement, the primary internal or external beveling may become obscured, causing difficulty with the identification of entrance and exit wounds. The morphology of associated secondary and tertiary fractures based upon the mechanics of their production is discussed as a means of establishing bullet entrance and exit sites.

Diameter of cranial gunshot wounds as a function of bullet caliber

Determination of bullet caliber becomes increasingly important in homicides where the bullet is missing. In cases with entrance wounds to bone that are circular and well defined it may be tempting to measure the defect and offer suggestions about bullet caliber. For this reason, the relationship between wound diameter and bullet caliber was examined using cranial bones from autopsy cases. The minimum diameter of 35 cranial wounds produced by .22, .25, and .38-caliber bullet was measured. The relationship of minimum wound diameter to bullet caliber was examined using a one way analysis of variance. Fishers least significant difference test revealed no significant difference between .22-caliber and .25-caliber wounds, while the .38-caliber wounds were significantly different (P < .001) from .22-caliber and .25-caliber wounds. Variation in wound size resulting from such factors as bullet shape, surface treatment, strength characteristics, loss of gyroscopic stability, intermediate targets, tangential impacts, and existing fractures are discussed. Also, the large variety of calibers available are noted as complicating the prediction of caliber from wound size. In view of these factors caution is recommended in any attempt to determine precise bullet caliber from the minimum dimensions of the cranial gunshot entrance wound.

Recognition of Cemetery Remains in the Forensic Setting

Cemetery remains exposed through vandalism or natural phenomena are frequently brought to the attention of law enforcement agents or medical examiners. Although it is often difficult to distinguish cemetery remains from those of medicolegal significance, clues to their origin may exist. Characteristics consistent with cemetery remains include physical characteristics associated with the embalming process. Characteristics indicative of cemetery remains include functional or ornamental artifacts associated with the coffin, devices used in embalming the body, and elevated levels of embalming chemicals in the soft tissue.

Atypical gunshot exit defects to the cranial vault

Cranial exit wounds typically display external beveling, however, variation has been noted in the literature due to keyhole phenomena and pre-existent fractures. Two cases of atypical exit morphology are presented with features mimicking blunt trauma. In both instances radial fractures created by the exiting impact allowed passage without producing exit beveling. A working knowledge of the biomechanics of bone fracture, radiographs and low power microscopy are essential elements for the proper interpretation of such exit wound fractures.

Characteristic Features of Entrance Wounds from Hollow-Point Bullets

Several cases of gunshot wounds produced by hollow-point bullets showed characteristic central tags. These apparently arise from sparing of the skin surface by the hollow point cavity when the bullet strikes the skin tangentially. This unique feature may be helpful in assessing entrances of perforating wound tracks or other cases where the bullet is either not available or unknown.

Effects of human decomposition on bullet striations

Five different types of bullets, representing the major materials used in centerfire handgun and rifle ammunition, were inserted into the cranial, chest and abdominal cavities, muscle and adipose tissues of a fresh cadaver. The bullets were retrieved after the body was 90% decomposed. Observation and comparison of before and after photographs let each bullet serve as its own control. Results indicate the reactivity of bullet materials and the body region are significant factors affecting the corrosion process and may obscure rifling striations.

The meaning of an accessory projectile

A previously expended pistol casing was removed from a gunshot wound after an apparent accidental shooting. Examination of this foreign body indicated it had ridden the bore ahead of the bullet. Further investigation disclosed this as a deliberate but ignorant means to load an already loaded weapon. The assailants then fired at a passerby and killed him. Disclosure of the foreign body by X-ray, recovery and examination at autopsy were used to corroborate the circumstances and allowed charges of criminally negligent homicide to be placed.

Identification of Gunpowder in Healed Wounds

A woman received a contact gunshot wound to the abdomen from a .22 caliber revolver. She recovered only to succumb to another gunshot wound six months later. The initial wound was dissected and multiple intact granules of round flake gunpowder were recovered. Cross sections of granules were clearly identifiable in histologic slides. Recovery of intact powder in remote wounds has not been previously described and may help classify the ammunition and weapon used to produce the injury.

Matching bullets to bone impact signatures

When bone is penetrated or perforated by a bullet, the bullets impacting surface is often uniquely modeled by the fractured bone. Reconstructing bone with simple super-imposition of the bullets contour lines allows matching of a particular bullet to its specific bone defect.