Book Excerpt: Recovering Barefoot Evidence
Written by William J. Bodziak   

An excerpt from Forensic Footwear Evidence by William J. Bodziak

 

The Human Foot

 
The human foot is a complex structure that acts as the interface between the body and the ground. Figure 1 depicts two views of a foot and its 26 bones. Included are the talus (anklebone), the calcaneus (heel bone), the 5 tarsal bones (cuboid, navicular, and 3 cuneiforms), 5 metatarsals, and 14 bones of the toes called phalanges. Each foot also has over 100 muscles, tendons, and ligaments and two primary arches—the longitudinal arch between the heel and forefoot and the transverse arch, which runs across the ball of the foot. The foot can move in four directions known as plantar-flexion, dorsi-flexion, inversion, and eversion. Biomechanical descriptions of foot function are complex and vary when walking versus running but a very basic accounting of the gait cycle involves the foot relaxing (pronation) as it first makes contact with the substrate, then moving forward, distributing its weight from the heel area through the forefoot, and, finally, becoming rigid (supination) allowing the foot to more efficiently push off and propel itself. This sequence of events and how it is carried out is not precisely the same in each individual. Not all individuals’ feet function in a perfect or “normal” way. The mixed morphology and function of individuals’ feet provide reasons for variance in the features it leaves in its barefoot impression. In addition to shape features, feet may also have other noticeable pathologies. A few of these are blisters produced by a shoe repeatedly rubbing the skin, corns on toes, calluses on the bottom of the feet that result from a thickening of the skin where shoes repeatedly press, plantar warts, and hammertoes where the end joints of a toe bend downward. When present, these and other characteristics may be reflected in a barefoot impression or transferred to the inner liner of a shoe.

Figure 1—The human foot includes 26 bones: the phalanges (1); the metatarsals (2); the cuboid, navicular, and (3) cuneiforms; the calcaneus (4); and the talus (5).
 
Recovery of Barefoot Evidence
 
Two- or three-dimensional barefoot impressions are recovered using the same methods, materials, and procedures used for footwear impressions. The majority of naked or sock-clad foot impressions are found on interior surfaces. Of those a great many are in blood; thus, every consideration should be made regarding recovery of the original impressions as well as the utilization of enhancement methods at the scene or in the laboratory. Impressions produced in blood with a naked foot will typically last for only a few steps before the blood has been consumed. Socks are able to absorb and hold a larger quantity of blood than the naked foot and consequently scenes involving bloody sock-clad feet usually include a greater number of impressions. Scenes involving blood-soaked sock-clad impressions of both left and right feet could easily include dozens of impressions. Figure 2 depicts what happens after a blood-soaked sock has produced several prior impressions. The pressure of each prior impression has forced some of the blood to the outer perimeter whereas much of the blood beneath the feet and toes has been consumed. The result is an impression with a lighter interior and darker borders in some areas. Areas of the sock that have acquired blood but are not under the pressure of the foot will also result in some sporadic deposition of blood as seen in Figure 2 where the bloody sock makes contact between the toes and metatarsal ridge. Depending on the substrate and the thickness of the sock, the weave pattern produced on a sock-clad impression can range from very obvious to nondetectable. Figure 3 depicts one of several bloody sock-clad impressions from 14 tiles recovered and submitted for examination. Very good correspondence existed between the left and right feet of a suspect. Because the investigators recovered the actual tiles, subsequent laboratory chemical enhancement also developed small patches of latent skin ridge patterns that were produced after the perpetrator removed his socks before departing the scene. The latent ridge patterns were identified with the suspect’s feet by a latent fingerprint examiner.
 

Figure 2—Blood-soaked sock-clad impressions can hold much blood and produce many impressions at a crime scene. With each impression, blood is forced toward the perimeter of the foot and toes as well as deposited on the substrate. This impression shows the sock fabric, evidence of blood forced toward the perimeter, and lighter quantities of blood remaining in the pressure areas.
 

Figure 3—A case example of a sock-clad impression and corresponding features of the suspect's known right foot.
 
A significant potential piece of evidence that is often not considered is the footwear of a person suspected of leaving naked or sock-clad bloody impressions. If the perpetrator had accumulated blood on his or her feet or socks and then placed the shoes back on their feet as a person typically would when departing the scene, the inner surfaces of the shoes would likely contain detectable traces of human blood with the victim’s DNA profile. Thus the inner surfaces of footwear of a suspect believed to have left bloody sock or naked foot impressions during the commission of a homicide may be harboring valuable evidence that could link him or her to the victim’s DNA.
 
At any homicide scene involving bloody footprints, the feet of the victim should also be documented to determine if they were shod, naked, or sock-clad and if any of the bloody impressions at the scene could be theirs. If their feet contain a weight-bearing pattern of blood, this indicates they may have produced impressions. Since deceased victims cannot provide known weight-bearing standards of their feet, the shoes of the victim should be seized as they may contain useful inner sole impressions that could be used as known standards. Figure 4 depicts a victim’s foot on the left that has walked through blood as evidenced by the blood staining on the weight-bearing areas of the foot. The foot on the right contains blood that spilled onto the victim’s foot and flowed around the side of the ankle into some of the flexion creases, but that blood was not acquired because of the victim walking through the blood.
 

Figure 4—A weight-bearing blood pattern on the foot on the left resulted from walking in blood, as distinguished from the foot on the right, which has some blood that has flowed down around the ankle and onto the foot.
 
In some instances, recovered footwear may be linked to the crime scene impressions or the presence of the victim’s blood on or in the shoes, but when those shoes were recovered they were not being worn by the accused. The discovery of the shoes may be a product of a search warrant or because the footwear were discarded by the perpetrator and later discovered because of information provided by an informant. In some cases, when the accused is confronted with the shoes, he or she will admit ownership. If ownership is denied, the person should not be allowed to handle or wear those shoes as these actions can only interfere with subsequent examination. Shoes of an unknown wearer should be preserved for DNA evidence that may link the person to the owner and/or victim’s blood.
 
Obtaining Known Standards
 
Before any physical comparisons are conducted, known standards of the feet of the suspected person or persons must be obtained. Depending on the facts of a case, in addition to those of the primary suspect(s), obtaining exemplars of feet may extend to others for purposes of exclusion. Known standards for impressions on firm substrates like tile or wood floors require weight-bearing inked impressions of the feet. Crime scene impressions in soft substrates like soil or sand require the addition of three-dimensional impressions in similar soft substrates and/or Biofoam.  For those examinations that involve the question of who was the primary wearer of the shoes, in addition to weight-bearing inked impressions, other shoes the suspect has worn, preferably of a similar type, may provide good known standards. Depending on the features found within the questioned footwear, casts of the forefoot region of the suspect’s feet may also be necessary. In all cases, photographs of the feet of the suspect should be obtained as well as shoe sizing information obtained by measuring their feet. Not every exemplar is necessary for every barefoot examination, but when multiple ones are taken, they should be taken with the least messy methods first and the messiest methods last.
 
About the Author
 
William J. Bodziak holds an MS in forensic science and has spent over 44 years in the field of footwear and tire evidence. He created the first technical conferences on footwear and tire evidence held in 1983 and 1984, taught the subsequent forensic footwear courses at the FBI Academy, and organized the first International Symposium on Footwear and Tire evidence at the FBI Academy in 1994. He has instructed classes in the forensic examination of footwear and tire evidence on over 150 occasions, and has provided testimony on over 500 occasions. He has written three other books, several book chapters, and many journal articles. He has been an active member and participated in numerous professional organizations throughout his career.

 

 
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