Forensic Spoorology: Seeing and Understanding Human Behavior through Observation, Classification and Interpretation of Spoor Evidence

1. What they did

The author, a supervisory criminal investigator with the U.S. Marshals Service, has been tracking for four decades. He set up and commanded two Marshals tracking units, in Alaska (1998 to 2002) and Wyoming (2003 to 2006), and was certified by them as a Certified Master Scout Tracker in 2004. In this master’s thesis he sets out to lay a foundation for tracking as a forensic science, which he calls “spoorology”, that courts could rely on.

His questions were:

• Can tracks and signs, observed, classified and interpreted in a systematic way, meet the accuracy courts require?
• Can this method include or exclude suspects?
• Can human behaviour be recognised in a trail of footprints?

He reviewed writing on human behaviour, gait (the way people walk), tracking and footwear evidence, and court cases on shoeprint and tracking evidence. He then built a framework from Newton’s laws of motion, the Behavior, Gait, Spoor (BGS) paradigm, and a step-by-step method for reading a trail, the Observation, Classification and Interpretation of Spoor Evidence (OCISE) algorithm. OCISE has three stages: describing the prints themselves (spoor platting), the walking pattern (gait platting) and what the trail says about the person’s state of mind (behaviour platting).

He tested OCISE in two experiments in a flat riding arena at Fort Leavenworth, with five adult trackmakers, each in different shoes:

• Spoor Analysis Lanes. Each trackmaker walked down their own 25 m lane while he watched, to record a “baseline” of how each person walks normally.
• Incident Reconstruction Area. Out of his sight, in a 25 by 75 m area, the trackmakers acted out three situations, alone or in groups: walking home after hearing of a death in the family; being lost and disoriented at dusk while hiking; and checking whether police were watching a family marijuana plot. He then read their trails to identify each person and their behaviour.

He also included two real cases written by other trackers: a Virginia game warden and an Alaska State Trooper.

2. What they found

Identifying the trackmakers

• All prints were the clearest class of print and showed full detail. Each trackmaker’s shoes had a different tread, which separated them.
• Foot lengths ranged from 11.5 to 13.5 inches. Every trackmaker had a different overall track length, and nearly all other measurements also differed (the exceptions were sole length for Z2 and Z3 and heel length for Z3 and Z4).
• From the measurements he estimated each person’s height and weight range.
• Every trail in the incident area was matched to its trackmaker’s baseline from the lanes.

Reading behaviour

• In the lanes, all five were read as walking, turning, stopping, and sitting or standing; none were running, slipping or crawling.
• In the incident area, all five were recorded as showing thinking or planning, panic or fear, hurrying and being out of control at some point, as well as quiet and calm moments. None were recorded as nervous or aggressive. In one situation, when several trackmakers moved over the same ground, the trails briefly had to be sorted out.

The case studies

• Virginia: a game warden followed the trails of people who ran from him for about 300 yards. Stride length and a sudden change of direction showed they had run, and a cleared spot behind a tree showed where one had hidden to watch. He identified that person by shoe prints. Five people were found, and the track evidence was used in court.
• Alaska: a trooper followed two sets of tracks at night in snow by flashlight. Strides over 40 inches showed running; shortening strides showed slowing to a jog; the tracks showed where both stopped and looked back, where they split up, and where one lay down in the snow behind a box.

Certification

He found no universal tracker standard in the United States: tracking companies and agencies each had their own. He proposes one in an appendix: a written test (70% to pass) and field problems, with six levels from Certified Apprentice Tracker I to Certified Master Tracker.

3. What they concluded

• The author concludes that human behaviour can be identified in footfall patterns and trails, and that the tracks hold all the walking and state-of-mind information, if experienced trackers observe, classify and interpret them.
• He states that the experiments were too small to give statistical accuracies, but give useful qualitative indications.
• Reading a trail first-hand is stronger than interpreting someone else’s recorded data, especially for reading behaviour.
• The greatest challenge is the skill level of the tracker. Tracking needs more research, education and training before it is accepted as a forensic science.
• He recommends that investigators and crime scene staff be trained to be “track aware”, so tracks are not destroyed before a tracker can read them.
• Further research: harder ground, vegetation and slopes; longer trails; tracker eye fatigue; error rates; whether tracking first at a crime scene leads to more evidence; telling apart the tracks of victims, suspects and witnesses; and universal tracker certification.

4. How tracking was or was not used

Tracking is the subject and the method. The author read and measured footprints and trails, and used what he calls the deliberate trailing method, finding every step, to identify trackmakers and interpret their behaviour. The case studies describe trailing people who had fled, reading stride length, changes of direction, stops, hiding places and shoe tread, in woodland and in snow at night.

5. Tracker or observer certification

The author, who did the tracking in the experiments, reports that he was awarded Certified Master Scout Tracker in 2004 through the certification process of the U.S. Marshals Service for the Districts of Alaska and Wyoming, an internal standard. The two case-study trackers (a Virginia game warden and an Alaska State Trooper tracker) are not described further. The thesis does not report a test of how accurately the behaviour readings matched what the trackmakers actually did.

6. Other technologies, skills or innovations

• A new vocabulary and set of acronyms for forensic tracking, and a recommended tracker vocabulary (Appendix E).
• A Uniform Scale Format Synch Matrix for recording every part of a trail (Appendix B).
• A Foot Impression Reference Matrix to estimate height and weight from shoe size and print.
• A tracker crime scene kit for field experiments (Appendix C).
• Recommended tracker certification standards (Appendix D).