Do Resistance and Use Of Force Affect Accuracy Of Sobriety Testing?

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Will a foot chase, a physical struggle, or the use of non-deadly force on a drunk-driving suspect affect his ability to perform field sobriety testing accurately?

The suspect’s lawyer might like a judge or jury to think so–but findings from a new, first-of-its-kind study suggest otherwise.

The study, led by Dr. Jeffrey Ho of the Hennepin County Medical Center and the Meeker County SO in Minnesota, was inspired by a court case in New York State involving a driver who was stopped for speeding and subsequently fled on foot in an effort to avoid arrest for suspected OWI (operating [a vehicle] while impaired).

During apprehension, the suspect received a six-second CEW exposure to the back. Several minutes later, he totally failed a standardized field sobriety test (SFST). At trial, his lawyer blamed the failure on “lasting neurocognitive and psychomotor impairment” caused by the CEW, despite a “significant amount” of alcohol in his system.

Ultimately this gambit was unsuccessful, but, Ho writes, it “did initiate the question of whether or not a suspect’s resistive actions or a LEO’s use of force…could alter the result of the SFST.”


Using 57 LEO and CO volunteers from a police training facility in Arizona, Ho’s team tested SFST performance against five stressors that commonly occur on OWI stops.

First the subjects, mostly males and ranging in age from 19 to 55, were given a full- battery field sobriety test, including horizontal gaze nystagmus, walk and turn, and one-legged stand, as a baseline marker.

Then they were randomly assigned to play the part of a resister in one of five scenarios:

  • a five-second TASER X26 CEW exposure, with probes deployed to the back from about seven feet away;
  • a 100-yard sprint to simulate a foot pursuit, with a tight S-curve weave in the middle and a five-yard crawl at the end;
  • a 45-second fight against a padded opponent, in which they were “encouraged to punch, kick, push, and use elbow and knee strikes” while being physically harassed, blocked, and pushed during constant contact;
  • a hide-and-seek exercise with a K-9, in which the dog ultimately chomped onto the volunteer’s padded arm for 20 seconds while the “suspect” tried to shake him off;
  • a stream of 10% OC spray to the face and neck (with eyes shielded by swim goggles), followed by a 90-second decontamination process.

Once the assigned scenario was completed, each volunteer was again given the full SFST.


During the pre-scenario field testing, three volunteers “stepped off the line once” during the walk-and-turn component, resulting in a single penalty point given each of them.

After the stress scenarios, however, “no subject received penalty points for any factors of the SFST,” Ho reports. A few complained of dizziness, lightheadedness, vomiting, or minor abrasions from falling during the scenarios, but all were capable of performing the sobriety tests and all passed with perfect scores.

“Our study suggests that significant suspect resistance, fleeing, or the application of common LEO force options [do] not deteriorate SFST screening accuracy when performed 10-15 minutes after the resistance, fleeing, or use of force event…. [W]e also did not find any correlation with stress from resistance, fleeing, or use of force…causing neurocognitive or psychomotor impairment that would prevent a person from participating accurately in a SFST.”

Although the subjects were not tested “against every possible physical or emotional stressor” that could be present in an OWI stop, the study has “important implications for LEOs in the field and legal professionals in the justice system,” Ho writes. “It should reassure LEOs to know that they can rely on their training, experience, and the validity of the SFST even…where resistance, fleeing, or use of force has occurred.”

The full study, titled “Effect of simulated resistance, fleeing, and use of force on standardized field sobriety testing,” appears in Medicine, Science and the Law, the official journal of the British Academy for Forensic Sciences. A free abstract is available at: http://msl.sagepub.com/content/early/recent.

Our thanks to Atty. Michael Brave, National/International Litigation Counsel to TASER International, Inc., for alerting us to this study. Dr. Ho serves as medical director to TASER International, and another member of the research team, Dr. Donald Dawes, is a medical consultant to the company. Ho can be reached at: hoxxx010@umn.edu

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