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Footwear

Footwear impressions are one of the most underutilized evidence types. They are present at practically all crime scenes and can be recovered from a number of different surfaces. They don’t necessarily have to show the whole footwear impression to be of value to the forensic scientist. The scientist is only concerned with the quality/level of detail in the impression. Hence a partial impression on a smooth hardwood floor that is recovered with a gel lifter may be of more use than the full length impression in snow outside the property. This is important to remember at the crime scene – it is better to spend your time searching for a better quality footwear impression using oblique light than submitting the first impression that you see. At the laboratory the shoes from a suspect can potentially be identified or excluded as having made a crime scene impression. If the laboratory is unable to make a definitive statement during the comparison the shoes can be linked to the crime scene impression by degrees of association.

Footwear Intelligence

Crime scene impressions have the potential to yield certain fast-track intelligence; manufacturer and design searches. When you find a footwear impression at a crime scene you may email an image of this impression to dps.footwear.intelligence@alaska.gov along with pertinent information (location, date of offence, offence type and anything else that you feel is relevant to the case). These impressions will then be searched through an online database ARC (Alaskan Reference Collection) which has over 34000 outsole designs on it. If the sole design is found on the database an intelligence report will be generated by the laboratory and emailed to the submitting officer. This service aims to return a result as quickly as possible to aid the officer in the collection of known footwear. The photograph that the attending officer takes is subject to all the usual requirements for crime scene photography of footwear impressions (L shaped scale placed in same plane as the footwear impression, camera perpendicular to the impression, fill the frame with the impression, obliquely light the impression).
 
The first thing an attending officer should do once they have secured the scene is to preserve areas where the suspect could possibly have stepped. Many footwear impressions may not be immediately visible therefore entries and exits should be preserved for potential impressions. Traffic at the crime scene should be kept to an absolute minimum and where necessary the officer should use stepping plates or walk close to walls. If a footwear impression is located outside efforts should be taken to preserve the impression from the elements prior to suitable recovery.
Wherever possible the officer should submit the physical item bearing the footwear impression to the lab for recovery. Often times this is not possible so the officer must evaluate the impression and decide on the best course of action. The first decision what type of impression is present, this can generally be broken down into 3 categories – 3D, 2D and latent. Officers recovering footwear impressions are encouraging to spend some time looking for 2D or latent footwear impressions as these impressions are generally of much higher evidential value. Footwear impressions should always be photographed prior to attempts to recover.
3D footwear impressions in snow, sand, mud, dirt are one of the most visible evidence types especially in a climate such as Alaska’s. Before attempting to recovery any 3D impressions a series of photographs should be taken, these will complement any casts and document the impression in its original state, just in case the impression is destroyed during recovery. Before taking any photos any loose debris (that may have accumulated there after the impression was deposited) can be removed from the impression. Anything that is embedded in the impression, however loosely, should be left in place. Comprehensive photography of the crime scene including overall and mid-range photographs (including placards) should be taken. A close up photograph should then be taken from a 90° angle. The photo should ideally be taken using a tripod to ensure that it is perpendicular to the impression. The impression should fill the frame; this means the length of the footwear impression should fill the widest dimension on the screen of the camera. An L shaped scale should be placed next to and in the same plane as the impression. If the impression is 6” (15cm) down in fresh snow, you should dig a small trench 6” down next to the footwear impression (taking care not to cave the sidewall into the impression) and place the scale in it. Experiment with light from different angles to best illuminate the impression, around 10-20° usually works best. Take at least three photos using light from different sides as they will show different details within the impression. The placard number should be visible in the photograph.
If the impression is in snow/ice introducing contrast will help to get a better photo. To do this spray snow print wax or spray paint at a shallow angle around 6-10” (15-25cm) from the impression. A thin coat and oblique light will give the best results.
footprints