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Forensic gait analysis is the identification of gait features and patterns of subjects seen on Closed Circuit Television (CCTV) and from footprints forming a gait pattern left at the scene of a crime. Studies have shown that more than 30% of people wear shoes that are within a two shoe size differential, which can affect the gait phase and gait time parameters and impact on the class level distinction during forensic examination.Forensic gait analysis is the identification of gait features and patterns of subjects seen on Closed Circuit Television (CCTV) and from footprints forming a gait pattern left at the scene of a crime. Studies have shown that more than 30% of people wear shoes that are within a two shoe size differential, which can affect the gait phase and gait time parameters and impact on the class level distinction during forensic examination.

Background
Forensic gait analysis was first defined by “Kelly (2000) as the identification of a person or persons by their gait or features of gait, usually from closed circuit television (CCTV) footage and comparison to footage of a known individual. Gait recognition was later defined by Grant (2006) as the process of identifying people by the unique characteristics of their manner of walking, where features are extracted from a person’s gait in order to recognize them.”1

The height of an individual can be determined by his/her footprint and shoeprint.2,3 The foot tends to be approximately 15% of the person’s average height.4,5 At times series of footprints are left at the scene of a crime forming a recognizable gait cycle. The information gathered during examination of footprints and also on closed circuit television (CCTV) may be of value for forensic application. Individual characteristics of the footprints and gait, like numerous creases, flatfoot character, horizontal and vertical ridges, corns, deformities, step length, stride length, and stance phase, swing phase, step time, stride time, cadence, and velocity observed on CCTV can help the forensic examiner in cases pertaining to criminal identification.4

Studies by Schwartzkopf have shown that 34.9% of the subjects wore shoes within a two full shoe size differential, and 11.9% wore shoes within a full three shoe size differential.6 A study by Nixon showed that shoeprints left at the scene of a crime may be from shoes fitted properly only 25–33% of the time.7 Studies by Kagan8,9 showed that osseous and soft tissue changes occurred, affecting the plantar weight distribution when an individual wore different sized shoes within three full sizes. These plantar weight pressure distribution changes occurred in the areas of digital impression, web ridge line, web space, and arch line so that comparison of footprints and “exemplars” would be more difficult to verify degrees of certainty. 

Would wearing shoes sized within a three full size differential also affect the parameters of gait or would the gait pattern remain consistent regardless of shoe size?

Methods
An experiment was conducted in May 2013 using the Noraxon Myopressure System to evaluate the gait of a consenting individual (59 year old male, 188lbs, 69inches, 4 month s/p surgical repair of a right Achilles tendon rupture) wearing shoes, sized 8M, 9W, 10M, 11M. The subject normally wears shoes in the 9–9.5 medium to wide width range. Even though the subject was four month out from a post surgical repair of a ruptured Achilles tendon, he had healed and was walking without a noticeable limp and without the aid of any gait assistance devices. The purpose of this experiment was to determine if gait parameters would be affected.

The Noraxon Myopressure system for stance, balance, and gait analysis allowed access to more useable information through an unimpeded and uninhibited wireless pressure insole set up, with no pre-calibration requirements, and no expendables or fee per analysis. The soft insoles utilize reliable and durable technology comprised of around 240 sensors per foot for accurate data acquisition from initial heel contact through gait roll-off.

The system allowed for superior subject and set-up flexibility in movement and measurement with two lightweight cables from ankle to wearable receiver. Before completing the tests, the subject was told to walk shod with pressure insole set, size medium, until a level of comfort was achieved. Then recording was started while the subject continued walking at continued speed of choice. After 60 seconds the recording was stopped and data was instantly averaged in the automatic bilateral gait report from which comparisons and kinetic results were drawn. This was repeated with the subject wearing the same make and model of shoes sizes 8M, 9W, 10M, 11M in a randomized controlled order.

Data Results of Gait Phase Parameters

GAIT  PHASE PARAMETERS

SIZE 8M

SHOE

SIZE 9W

SHOE

SIZE 10M

SHOE

SIZE 11M

SHOE

STANCE PHASE %

 

 

 

 

                                    LEFT

66.5

63.2

66.2

65.3

                                                RIGHT

66.8

67

68

67.9

SWING PHASE %

 

 

 

 

                                     LEFT

33.5

36.8

33.8

34.7

                                     RIGHT

33.2

30.3

34.2

33.2

STEP LENGTH  in cm

 

 

 

 

                                      LEFT

14

16

14

16

                                      RIGHT

15

15

14

16

STRIDE LENGTH  in cm

 

 

 

 

 

29

30

29

32

 

Table 1: Gait phase parameters

Discussion of Results
“The gait cycle is divided into a stance phase and a swing phase period for each foot. The stance phase portion of the gait cycle for each foot is that portion of the gait cycle which begins with heel strike and ends with toe off. During the stance phase, the foot bears body weight. This phase comprises approximately 60–62% of the full gait cycle.”10

The stance phase was 63.2% on the left extremity while wearing a size 9W shoe. When wearing shoes shorter and longer than the 9W, the stance phase was more prolonged. What is interesting to note is that the stance phase on the right extremity which was four months status post surgical correction of a ruptured Achilles tendon was 66.8% when wearing a size 8M shoe. More prolonged stance phases were noted when wearing the longer shoes, 9W, 10M, 11M. The right foot contracted s/p surgery and prior to completion of rehabilitation so that the proper shoe fit may have been the smaller size 8M due to functional changes. (See Table 1.)

“The midstance period starts at the end of the contact period, momentarily after toe off and ends with heel lift. It comprises approximately 40% of the stance phase of gait”.10

This was not evaluated. Double stance phase is that period of time in the gait cycle when both feet are in contact with the ground. It was also not evaluated.

“The swing phase portion of the gait cycle for each foot occurs between toe off and heel strike. During the swing phase, the foot swings from one step to the next and is non- weight bearing. It comprises approximately 38–40% of the full gait cycle.” 10,11

The swing phase was 36.8% on the left extremity while wearing a size 9W shoe. When wearing shoes shorter and longer than the 9W, the swing phase is shorter. (See Table 1.) What is also interesting to note is that the swing phase on the right extremity which was, as noted previously, four months status postsurgical correction of a ruptured Achilles tendon was 30.3% when wearing a size 9W shoe, that being the shortest swing phase wearing shoes. That may be due to muscle belly atrophy, possibly a lighter leg making it easier/faster to swing.

Step length is the linear distance between the point of initial contact of one foot and the point of initial contact of the opposite foot. In normal gait, both right and left step lengths are similar. We note similar lengths when shoes sized 10M and 11M are worn. We note a 1cm longer step length on the right when an 8M shoe is worn and a longer 1cm step length on the left when a size 9W shoe is worn.

Stride length is the linear distance between successive points of initial contact of the same foot. There is a 3cm difference noted in stride length in the various shoes. When wearing shoes sized 8M and 10M the stride length was 29cm. The stride length was 30cm when wearing a size 9W shoe and stride length was 32 cm when wearing an 11M sized shoe.

Data Results of Gait Time Parameters

GAIT  TIME PARAMETERS

SIZE 8M

SHOE

SIZE 9W

SHOE

SIZE 10M

SHOE

SIZE 11M

SHOE

STEP TIME  in sec

 

 

 

 

                                        LEFT

0.6

0.7

0.7

0.7

                                        RIGHT

0.6

0.7

0.7

0.7

STRIDE TIME in sec

 

 

 

 

 

1.3

1.3

1.4

1.4

CADENCE step/min

96

95

87

86

VELOCITY  km/h

.8

.9

.7

.8

Table 2: Gait time parameters

Discussion of Results

Evaluating Table 2 we note that the step time was identical in shoes sized 9W,10M,11M and was 0.1 sec faster in shoe sized 8M.

The stride time was faster when wearing size 8M and 9W at 1.3 seconds and 0.1second slower when wearing shoes sized 10M and 11M.

Cadence was fastest when wearing shoes size 8M and 9W and slowest when wearing size 10M and 11M shoes.

Velocity was fastest when wearing shoes 9W and slower when wearing shoes 8M, 10M, and 11M. (See Table 2.)

Conclusions
The subject approximated the scientifically accepted stance phase percentage of gait cycle when wearing a size 9W shoe on his left foot. When he wore longer and shorter shoes on the left foot, the stance phase was more prolonged possibly as a compensatory mechanism for wearing shoes not properly fitted and which required more energy to maintain stability or equilibrium. The subject approximated the scientifically accepted stance phase percentage of gait cycle when wearing a size 8M shoe on the right foot (four month s/p Achilles rupture repair) and the stance phase was more prolonged in the longer shoes which may be due to a contracture of the right foot after immobilization, atrophy of muscle belly after a period of immobilization, or even a smaller foot which would be fitted more properly by a shorter shoe.

The subject approximated the scientific accepted swing phase percentage of gait cycle when wearing a size 9W shoe on his left foot and the swing phase was shorter when he wore shoes shorter and longer. The subject had the shortest swing phase when wearing size 9W

Gait time parameters can be of value in CCTV (Closed Circuit TV) examinations. Qualitative gait is a non-numerical evaluation of movement. It has demonstrated class-level distinction but as of yet has not demonstrated unique distinction.”1 

It is difficult to draw conclusions from a study of a single subject. However the purpose of this paper is to raise awareness that there may be gait phase parameter and gait time parameter changes that occur when wearing shoes of different sizes which must be considered in forensic examinations. Further clinical trials of a large subject sampling would be useful to provide enhanced knowledge advancing the understanding of forensic gait observed in crime scene gait patterns and on CCTV, specifically step length, stride length, stance phase, mid stance phase, swing phase, double stance phase.

A special appreciation and acknowledgement of S&H Uniforms, 1 Aqueduct Road, White Plains, NY 10606 for providing the shoes in this experiment.

References

1. DiMaggio JA, Vernon W, Forensic Podiatry, Humana Press, p105, 2011.

2. Krishan K,  Estimation of Stature from Dimensions of Hands and Feet in a North Indian Population. J. Forensic Legal Med 2007:14(6):327-322.

3. Giles E, Vallandigham PH, Height Estimation from Foot and Shoeprint Length. J Forensic Science 1991 Jul;36 (4):1134-1151.

4. Krishan K, Estimation of Stature from Footprint and Foot Outline Dimensions in Gujjars of North India. Forensic Science International 2008:175(2-3):93-101.

5. Krishan K, Determination of Stature from Foot and Its Segments in a North Indian . Population. American Journal of Forensic Medical Pathology 2008:29(4):297-303.

6. Schwarzkopf R, Perretta DJ, Russell TA, Sheskier SC. Foot and Shoe Size Mismatch in Three Different New York City Populations. J Foot Ankle Surgery 2011:50(4):391-394.

7. Nixon BP, Armstrong DG, Wendell C, et al. Do US Veterans Wear Appropiately Sized Shoes? Journal of the American Podiatric Medical Association 2206:96(4):290-292.

8. Kagan BB, Comparing Static Shod Foot Impressions with Barefoot Foot Impressions.
98th Annual Conference of the International Association for Identification, August 2013, Providence Rhode Island.

9. Kagan BB, Comparing Dynamic Shod Foot Impressions with Dynamic Barefoot and Shod Impressions, https://www.forensicmag.com/articles/2013/10/comparing-dynamic-shod-foot-impressions-dynamic-barefoot-and-shod-foot-impressions. 10/28/2013

10. Root M,Orien WP,Weed JH, Normal and Abnormal Function of the Foot, Clinical Biomechanics Corporation, 1977, pp 127-128.

11. Uustal H, Baerga E, Gait Analysis, http:www.ncbi.nim.nih.gov/books/NBK27235/#_A8448

Dr. Bryan B. Kagan, DPM is a board certified podiatrist in private practice since 1980 in White Plains, NY. He specializes in Forensic Podiatry and Podiatric Medicine and is on staff at White Plains Hospital. He has lectured nationally and published several articles on forensic podiatry and will be teaching an introductory elective course at the New York College of Podiatric Medicine. He is Secretary–Treasurer of the American Society of Forensic Podiatry. 122 West Post Road, White Plains, NY 10606; westfootdoc@gmail.com; http://www.bkagan-dpm-forensicpodiatry.com

Sally Crawford, MS in Biomedical Engineering, is a clinical gait and sports performance specialist at NORAXON. She has worked with sports and medical researchers and clinicians monitoring performance and studying ergonomics in the workplace and product design. 15770 N. Greenway-Hayden, Suite 100, Scottsdale, AZ 85260; sally.crawford@noraxon.com

 

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