Crime Scene Investigator Network Newsletter

Introduction: In a recent joint explosives exercise with the state fire marshall, an experiment was conducted to determine the extent of damage that an explosive blast would cause to undeveloped latent prints. The interior of the car and items placed in the car were prepared with latent prints. The goal was to recover and process the items for latent prints after the detonation of two explosive devices.

Method: A compact two-door passenger car was donated for testing purposes. The state fire marshal provided two explosive devices to create a simulated postblast crime scene. A harvested soybean field was selected to provide sufficient safe space for the expected distribution of debris. Two explosive devices were placed in the target vehicle. The first explosive was a galvanized pipe bomb; it was placed under the vehicle dashboard near the operator pedals. This device measured approximately 2 inches in diameter and 10 inches in length and contained one stick (.25 pound) of symtex ammonium nitrate-based dynamite. Symtex is a high explosive with a velocity of approximately 18,000 feet per second. The second device was approximately two and a half pounds of Composition B. [Composition B is a mixture of cyclotrimethylenetrinitramine (RDX) and trinitrotoluene (TNT).] This mixture explodes at a velocity of 22,000 to 26,400 feet per second. The Composition B device was placed between the two front seats on a center console.

Prior to bomb placement, test prints were placed on several items (three air pistols, the plastic panel on the face of the speedometer, a seat belt buckle, and both exterior door handles). The test prints were created with sebaceous material from the forehead and careful touching of the surfaces. All latents were clearly visible with oblique lighting prior to the blasts. The locations of these latents were highlighted with a permanent marker to assist in the documentation and recovery. The air pistols were placed on the driver’s seat, the right rear passenger seat, and in the passenger side door compartment.

Results: The detonation of the pipe bomb caused fragmentation damage and only minor structural damage to the vehicle. The Composition B blast, however, was devastating. Structurally, the vehicle was severely damaged, and the recovery of the marked items was difficult and, in some cases, impossible. The outer panels of both doors flew nearly 110 feet and the roof landed approximately 100 yards from the vehicle. One air pistol was almost completely incinerated, another was never recovered, and only small pieces of the third air pistol were located. The largest piece recovered measured approximately 4 ½ by 1 ½ inches. The smallest piece was located approximately 56 feet away from the vehicle and the remaining pieces ranged to 106 feet away. The dashboard panel was completely destroyed, and the driver’s seat belt buckle was never located. The recovered marked items were analyzed using a Ruvis Krimesite Imager (with the aperture at 3.5). The ridge detail planted on the air been completely incinerated. Only very faint ridge detail was observed on the driver’s door handle, and the majority of this detail was burned beyond usefulness.

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