In this high tech world of DNA analysis, computerized bloodstain spatter analysis, and video imaging it seems a little mundane to talk about something as simple at shoe print analysis. Like fingerprint analysis, shoe print analysis has been around for a long time. However, in many cases foot prints are over looked at a crime scene, walked upon by responding officers or paramedics or just plain ignored. Fifty years ago when he only athletics shoes on the market were black and white high top sneakers that said "Keds" on the side shoe prints might not of had as much value. However, today there are over one hundred manufacturers of athletic shoes for both men and women. Each shoe with a distinctive pattern to their sole and the name of the brand in most cases stamped into the bottom of the shoe. Thus, a shoe print has become a much more vital piece of circumstantial evidence that can help place a perpetrator at the scene of the crime and possibly eliminate other persons of interest from consideration.
Look before You Leap
Plano, Texas Friday, July 4, 2008, Plano police arrest two men on suspicion of burglary after receiving a call about two suspicious men carrying property out of a house. An eye witness said that one of the men jumped up on a vehicle and scaled a retaining wall behind the apartment complex. The crime scene investigators found a footprint on the vehicle and photographs of the image were made. During the robbery interrogation, one of the suspects, Bruce Crawford, 18, said that he had information about the robbery and also about the shooting of a Yellow Cab driver. The murder of the Yellow Cab driver had, to this point, been an unsolved murder case. Police had released few details about the cabby's murder but Crawford divulged detailed information about the crime. The shoe print from the crime scene matched shoes owned by Crawford and he was subsequently arrested as the prime suspect in the cab driver’s murder.
At present the crime remains under investigation, however, the shoe print evidence represents a "tiny piece of evidence" that links Crawford to the murder according to Plano Officer Rick McDonald. A connection they might otherwise not have made.
Admissibility Issues
Like most all forensic evidence shoe prints can not directly prove that a suspect committed a crime. They can only provide a link to show that the suspect was present and or in contact with the victim or scene but they cannot provide the "when" or "under what circumstances" that link was made. In 2004, attorneys for Anthony Allen appealed his conviction of the 2001 burglary of the Standard Federal Bank in Fort Wayne, Indiana. The appeal was based in part on the admissibility of shoe print evidence and the testimony of several forensic experts. There appeal was that the shoeprint evidence was not relevant because the expert witness could not give a conclusive statement that Allen’s shoes were the only shoes that could have made the prints left at the bank crime scene. They cited Federal Rule 702 of the Federal Rules of Evidence and case law of Daubert v. Merrill Dow Pharmaceuticals, U.S. 579 (1993) in their arguments.
In November of 2004, the U.S. Court of Appeals for the Seventh Circuit upheld the conviction of Allen. The court decided that neither Rule 702 or the above cited case require that an expert witness be able to provide to the court a determinative or positive conclusion about any article(s) of evidence presented. Additional case law has demonstrated that when it comes to expert testimony the question of relevance does not require that the individual testifying as an expert have an opinion on the ultimate question to be resolved to satisfy any relevance requirements.
Analyzing Foot Prints
If a bloody foot print were left at a crime scene it would immediately receive attention, be photographed and become part of the bloodstain evidence file. However, for other shoe prints the crime lab must resort to other means to preserve the evidence data. Careful photographic records must be made of the shoe impression as well as the area around it. To form a permanent record of the impression itself it must be lifted or cast into a form that can be stored as evidence.
Capturing Shoe Print Evidence
Shoe print evidence can appear in dust on a surface like the vehicle in the Plano case, in dirt, mud and even in snow. There are a number of methods available for lifting a shoe print. The procedure is to use the least destructive method first. If the impression is in dry material like dust a piece of equipment called an electrostatic dust lifter can be used. A thin film with a black side and an aluminum coated side is used. The black side is applied to the impression while a high voltage charge is applied to the aluminum side. This charge results in an electrostatic charge that transfers the dry dust to the black side. The impression can then be observed using a high intensity light source at a thirty to forty five degree angle to the impression and in a darkened room. As with all aspects of foot print analysis photographs are taken under appropriate conditions to provide a permanent record of the findings.
Footwear sized adhesive lifters and gelatin based lifters can be used for impressions that are wet in origin. They can also be used with dry impressions and those that have been developed using one of the various types of fingerprint powders. Impressions left in mud or on a sandy beach can be lifted using Dental Stone. In this case a thick slurry of the material is carefully poured into the impression and then allowed to dry. When dry the solid impression cast is removed from the impression. If the surface that the print is on is highly textured a material called polyvinylsiloxane can be used to capture the print.
Impressions left in snow are generally photographed and a highlighting spray is used to enhance contrast. Such prints cannot be cast using Dental Stone because the weight of this material would collapse the snow. Snow Print Wax or aerosol paint is generally used in these situations to enhance contrast. Snow Print Wax or paraffin wax can be sprayed into the snow impression and allowed to solidify. Then several subsequent layers can be applied forming a casting that can then be removed from the impression.
Identifying the Print
The International Association for Identification has a number of Scientific Working Groups formed for the purpose of standardizing the methods for collection and identification of shoe pints. Use of these standardized procedures is intended to increase the credibility and admissibility of foot wear analysis data in the court room. A subscription service called SoleMate is available which provides to update data on over 12,000 sports, casual and work shoes. Basic features of the shoe are assigned a certain set of codes and then these codes are matched to the database to identify the most likely candidate shoes for a match. In much the same manner as a fingerprint is matched in AFIS the program presents the match candidates pictorially in the descending order of pattern correlation.
