Height Estimation from Foot and Shoeprint Length

1. What they did

When there is no trustworthy eyewitness description, footprints or shoeprints at a crime scene may be the best clue to a suspect’s height. The authors found that forensic textbooks offered almost no help, and that the one recent U.S. study (Robbins 1986) had weaknesses. So they set out to give a statistically sound way of estimating the height of modern Americans from their feet and shoes.

• Reviewing earlier work. They traced a century of studies of foot length and height, and checked how earlier figures (15%, 15.5%, 16%) had been used and sometimes misquoted.
• Foot length and height. They used two very large U.S. Army surveys: 6682 men (1966) and 1330 women (1977), mostly young adults. Height was measured standing, without shoes; foot length was measured in a box from the heel to the tip of the longest toe. They worked out the average foot length to height percentage and a regression equation for each sex.
• Testing the methods. They estimated the heights of 287 young male Army trainees, who were not used to build the equations, in three ways: Robbins’s 15%, their own percentage, and their regression equation.
• Shoe size. They built a table (Table 1) estimating height from U.S. shoe size, assuming the average foot is 19 mm (3/4 in.) shorter than the shoe size it is fitted to.
• Shoeprint length. At four tracking training sessions taught by Vallandigham in 1986 to 1987, they measured the height, foot length and shoe length of 84 male police officers in their everyday shoes. From this they built a table (Table 2) estimating men’s height directly from shoeprint length.

2. What they found

Foot length and height

• Foot length and height were moderately correlated (r = 0.678 for men, 0.693 for women).
• On average, foot length was 15.346% of height in men and 14.926% in women.
• Regression equations: men’s height (cm) = 3.447 × foot length (cm) + 82.206; women’s height (cm) = 3.614 × foot length (cm) + 75.065. About 70% of people fall within ±5 cm (men) or ±4.9 cm (women) of the estimate.
• Using the men’s equation on women overestimated their height by an average of 3.09 cm; using the women’s equation on men underestimated by 1.69 cm.

The test on 287 trainees

• Robbins’s 15% overestimated height by an average of 4.31 cm (and by 3.99 cm for the 6682 Army men, while underestimating the women by 0.83 cm).
• The authors’ percentage overestimated by 0.29 cm and their regression by 0.37 cm, a difference that was not significant.
• But the regression estimates varied much less from person to person than the percentage estimates (variances 21.71 versus 35.04, P < 0.001), so the regression is the more reliable method.

Shoes and shoeprints

• Shoe size adds uncertainty. Sole and heel styles differ between brands (in one study, prints of sneakers of the same size differed by up to 10.4 mm between brands, and some cowboy boots leave a print shorter than the foot). Fit varies too: even professionally fitted Army boots of one size were worn by men whose feet differed by 20 mm in length, and one person wore a sneaker 6.7 cm longer than his foot.
• People who need a wider shoe than cheap sneakers offer often buy a longer one. The sides of the shoe bulge, and in soft soil, mud or wet sand the bulge shows in the print.
• In the 84 police officers, shoes were on average 2.62 cm longer than the foot for “flats” (worn by 49) and 2.87 cm longer for “heels” (worn by 35).
• Table 2 gives men’s height for shoeprints from 24 to 34 cm, each with a spread of about ±6.35 cm expected to include 70% of men. For a print made by “heels”, the next smaller entry is used. No women’s table was possible, because there were no data on women’s shoe length.
• In a real case, Vallandigham estimated the heights of two suspects from their tracks leaving an abandoned vehicle; both estimates proved accurate to within an inch. Applied to the shoeprint found at the 1932 Lindbergh kidnapping, Table 2 gives 178.4 cm, close to the 177.8 cm the convicted man gave on a driver’s licence application.

3. What they concluded

• Foot length is about 14% to 17% of height, varying with age, sex and population: a larger share in children, men and tall people, a smaller one in women and short people.
• How foot length is measured matters: a bare print on a hard surface, a traced outline, a caliper measurement and a shoeprint all give different lengths. Robbins’s data suggest a bare footprint on a hard surface is 14.35% of a man’s height and 13.93% of a woman’s.
• For a quick estimate, the percentages work, but the regression equations give the same average accuracy with less scatter. A single 15% figure for both sexes overestimates men and underestimates women.
• Table 1 offers height from shoe size for both sexes; the authors prefer Table 2, which works directly from shoeprint length for men.
• A range of about 12.7 cm (5 in.) may not sound helpful, but it may still be more accurate than an eyewitness’s guess.
• Height estimated from any part of the body can never be exact and can only be discussed in statistical terms.

4. How tracking was or was not used

This is a measurement study rather than a field tracking study, but it is about reading human tracks. The shoe data were collected at tracking training sessions for police, taught by co-author Vallandigham. The authors note that forensic tracking specialists can identify footwear from track impressions (sole and heel shape, tread pattern, a welt), and that weather, temperature, region and terrain suggest what footwear to expect: a border patrol tracker on the U.S.-Mexican border in July expects sandals and tennis shoes, not snow boots. Weathering and aging of a print can change its size, and understanding this is an acquired skill. Besides foot and shoe length, a tracker can use foot width, stride length, trail width, pitch angle and pressure releases, and can often describe a suspect’s sex, height, weight, age, handedness, load, injuries, and mental and physical condition. The paper does not test these wider claims.

6. Other technologies, skills or innovations

• A measuring box built for the study, for measuring foot and shoe length.
• Conversions between U.S., English, French or Continental, and Mondopoint shoe sizes.
• A reprinted table by Cassidy (Royal Canadian Mounted Police) for estimating shoe size from shoeprint length in four shoe style groups.