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Applied Force During Prone Restraint

Is Officer Weight a Factor?

Kroll, Mark W., PhD, FAIMBE*†; Brave, Michael A., MS, JD; Kleist, Scott R.§; Ritter, Mollie B., MS, PA; Ross, Darrell L., PhD; Karch, Steven B., MD

The American Journal of Forensic Medicine and Pathology: March 2019 - Volume 40 - Issue 1 - p 1–7
doi: 10.1097/PAF.0000000000000457
Original Articles

Introduction It has been suggested that law enforcement officer (LEO) weight on the backs of prone subjects may cause asphyxia.

Methods Law enforcement officers used their agency-trained “local” single- and double-knee techniques, the “Wisconsin” 3-Point Ground Stabilization, and the Human Factor Research Group Inc single-knee tactical handcuffing techniques, and the weight force was measured.

Results Forty-one LEOs (36 men, 5 women) participated, aged 38.4 ± 8.3 years, and weighing 96.2 ± 19.4 kg. The double-knee technique transmitted more weight than single knee (P < 0.0001). Wisconsin technique force was lower than other single-knee techniques (P < 0.0001). Double-knee weight was 23.3 kg plus 24% of LEO's body weight. Mean values for local and Human Factor Research Group Inc single-knee were 30.9 and 32.9 kg, respectively. The Wisconsin single knee weight force was given by 15.4 kg plus 9.5 kg for a male.

Conclusions A double-knee technique applies more weight force than single-knee techniques. The Wisconsin single-knee technique provides the least weight force of single-knee techniques. Law enforcement officer body weight is irrelevant to prone-force weight with single-knee techniques. With double-knee restraint, it has a modest influence. Our data do not support the hypothesis of restraint asphyxia.

From the *University of Minnesota, Minneapolis, MN;

California Polytechnic State University, San Luis Obispo, CA;

LAAW International, LLC, Scottsdale, AZ;

§Police Department, Plymouth, MN; and

Valdosta State University, Valdosta, GA.

Manuscript received October 15, 2018; accepted November 10, 2018.

M.B.R. is an independent consultant. S.B.K. is a consultant cardiac pathologist.

There was no funding for this study, and all time was donated. M.W.K., M.A.B., D.L.R., and S.B.K. have been expert witnesses in use-of-force litigation or coroner's inquests.

The authors report no conflict of interest.

Reprints: Mark W. Kroll, PhD, FAIMBE, University of Minnesota, Twin Cities, Box 23, Crystal Bay, MN 55323. E-mail:

© 2019 by Lippincott Williams & Wilkins.