New Study Yields Unique Grid For Computing Suspect Speed In Officer Attacks

Print Friendly, PDF & Email

The latest time-and-motion study from the Force Science Research Center offers investigators and prosecutors a new tool to apply to officer-involved shootings and other threat encounters and presents trainers with a challenge in improving their students’ firearms skills.

The study’s core findings are captured in a unique grid chart that you can download and print out free by clicking here or typing http://forcescience.org/speedgrid.html into your browser. (If you print it out now, you’ll better understand the applications described in this article.)

This chart, called the Force Science SpeedGridTM, allows you to understand and demonstrate how to compute the speed at which a suspect is charging toward an officer with an edged weapon, for example, or running away after a confrontation.

“The chart expresses the speed in miles per hour,” explains Dr. Bill Lewinski, FSRC’s executive director. “This is a means of measuring and illustrating speed that is readily understood by civilians—jurors, for instance—and can help them appreciate the urgency that officers often face in force encounters.

“If you can show that a knife-wielding offender was running toward an officer at 15 mph, let’s say, it can help a layman better understand why that officer needed to shoot without delay before the suspect reached him.”

The chart has other possible applications, as well, Lewinski says. “It can help establish how fast an officer needed to move to escape a vehicular attack or help explain why an officer’s rounds struck a fleeing suspect in a particular location or at a particular angle or missed him altogether.

“In short, this is one more means by which reviewers can assess an officer’s actions and analyze the human dynamics involved in certain encounters. When an officer says, ‘The suspect was coming at me fast,’ you may now be able to explain just how fast.”

The study that resulted in the SpeedGridTM stretched across a 15-year period in which Lewinski conducted fitness evaluations of students entering the professional law enforcement program at Minnesota State University-Mankato, where he is a faculty member and where FSRC is headquartered.

Among other things, the testing involved the students sprinting for 50 yards and running for a quarter-mile to simulate a foot pursuit. This was done on a compacted sand-and-gravel track where each footfall left a visible impression.

“When I first started competing in track meets nearly 50 years ago, I noticed that people accelerated at different speeds,” Lewinski told Force Science News. “I also noticed that as each person accelerated, his or her stride changed. There is a fairly consistent style of movement that most people use as they drive forward. They start with short, quick steps, then take increasingly longer but quicker ones as they pick up speed.”

When testing the law enforcement candidates, Lewinski began periodically recording measurements of time, distance, and cadence of strides. “Each step a subject took connected to a different rate of acceleration and to a different length of stride,” he says. “Realizing this led to the idea of computing how fast the runners were actually traveling at the various stages of their acceleration.”

He estimates that he studied more than 1,000 individuals—“all kinds: short, stocky, fat, tall, lean, male, female, predominately in the age range of suspects officers are most likely to encounter in force situations.”

On average, he found that when youthful, vigorous, relatively fit people start to run, their first step takes about .35 of a second (not counting reaction time) and covers 1.5-2.0 feet. Their second step requires about .34 of a second and covers about 3.0 feet. Their third takes about .33 of a second and the stride lengthens to 3.5 to 4.0 feet…and so on. Typically, after 5 to 7 steps, people max out at about .25 of a second per 5.5- to 6.0-foot stride, which they can then maintain for a short period of time.

With the help of Dr. Bill Hudson, FSRC’s deputy director and head of the university’s Electrical and Computer Engineering Dept., Lewinski transformed his findings into a grid that allows you to convert stride length and speed into a miles-per-hour (mph) reading.

A suspect whose stride takes about 1/3 of a second and covers 4 feet, for example, is traveling 8.26 mph. If his stride has stretched to 7 feet and is down to 0.3 seconds, he’s moving at 15.91 mph. Sounds fast—and it is. But such a speed is not unusual for an “ordinary” person fueled by adrenalin. Olympic runners and some other rare superstars can accelerate to more than 27 mph. By comparison, a comfortable walking speed is 3 mph and a comfortable bicycling speed is 12 to 15 mph.

How do you know what stride length and time per stride to plug in to get a mph reading? Two possibilities:

1. Go with the averages, which are denoted in a box that’s included as part of the SpeedGrid TM. To illustrate:

Say you’re investigating an OIS in which an officer has shot and killed a fleeing suspect. The officer says she decided to shoot when the running offender, at a distance of about 25 feet, turned toward her and fired at her. But the suspect actually was hit at a point about 15 feet further away—and ended up shot in the back.

Using averages from Lewinski’s study, you can assume that the suspect was fully accelerated at the point the officer decided to fire. His stride would have been about 5.5 to 6.0 feet long and have taken about one-quarter second, so it was likely he was traveling at about 15 mph. The subject then covered the distance between the point that the officer decided to shoot and the point the bullet struck in just over one-half second – about the time it would take an officer to just align their weapon and fire.

“Knowing that, it’s easier to grasp that the suspect would have traveled more distance and could have turned his back to the officer between the time she decided to shoot and her bullet actually impacted.”

As another example, take a common training scenario: an edged-weapon suspect charges toward an officer from a distance of 21 feet.

Using averages, the attacker’s first stride is at about 3 mph. But accelerating, he can reach a speed of 12 mph or more and cover 21 feet in about 1.7 seconds in about 5 steps. Considering that the average officer requires about 1.5 seconds to draw and fire one round from a Level 2 holster (not even allowing for his initial reaction time), his disadvantage in this situation is made crystal clear.

2. In some cases, evidence at a scene may allow you to be more precise. “Often runners leave marks on a surface that you don’t have to be a tracker to see,” Lewinski says. “You may be able to see where they dug their toe in to start and then perhaps see where the front edges of their shoes bit into the surface at each stride.

“If someone hasn’t disturbed it, this kind of forensic evidence can often be detected on asphalt and other hard surfaces as well as on dirt, sand, and grass.” You can measure these markings to determine stride length.

If you’re fortunate enough to have video of the suspect running, you can clock the timing of his stride and then find mph on the SpeedGridTM. “If you don’t have an exact time measurement,” Lewinski says, “you can still plug in the average as an approximation.”

Here, the physical characteristics of the suspect may help you refine your calculations. “Large, lumbering people will likely have a stride time slower than average,” Lewinski points out, “and more agile, athletic body types may be faster.

“What you come up with won’t be exact, but you can get a good estimate that’s meaningful in the average person’s frame of reference.”

In some cases, the chart may be useful in measuring an officer’s speed of movement. In cases where officers are targeted in vehicular assaults, for example, it’s sometimes claimed that the officer could simply have stepped out of the way. But could he?

A car coming at an officer at just 10 mph covers nearly 15 feet every second. “Figure that the officer requires 1/3 of a second to react and then takes 2 lateral steps of about 1/3 of a second each, moving as fast as he can,” Lewinski suggests. “That means it takes nearly a full second for him to cover only about 3.5 feet, and that may not be enough for him to safely clear the oncoming car—unless he’s Superman.”

The ability to accentuate the speed at which people can move underscores a challenge to firearms instructors, Lewinski points out. “When you state a running suspect’s speed in miles per hour, it’s easy to understand why officers often miss when trying to shoot under those circumstances.

“In simulator scenes, the threat usually occurs in the middle of the screen, rarely or never running across it, even though lateral movement in officer-involved shootings is very much a real-world fact. Officers typically will miss in shooting at a suspect dashing across their line of sight because they usually aren’t trained to properly lead a target that can be running at 15 mph or more.

“Hopefully, the SpeedGridTM chart will motivate instructors to expand their training to include fast-moving targets and thereby improve both their officers’ hit ratios and personal safety.”

GDPR

  • Privacy Policy

Privacy Policy

Effective date: January 06, 2019

Force Science Institute, Ltd. (“us”, “we”, or “our”) operates the https://www.forcescience.org/ website (hereinafter referred to as the “Service”).

This page informs you of our policies regarding the collection, use, and disclosure of personal data when you use our Service and the choices you have associated with that data. Our Privacy Policy for Force Science Institute, Ltd. is based on the Privacy Policy Template from Privacy Policies.

We use your data to provide and improve the Service. By using the Service, you agree to the collection and use of information in accordance with this policy. Unless otherwise defined in this Privacy Policy, the terms used in this Privacy Policy have the same meanings as in our Terms and Conditions, accessible from https://www.forcescience.org/

Information Collection And Use

We collect several different types of information for various purposes to provide and improve our Service to you.

Types of Data Collected

Personal Data

While using our Service, we may ask you to provide us with certain personally identifiable information that can be used to contact or identify you (“Personal Data”). Personally identifiable information may include, but is not limited to:

  • Email address
  • First name and last name
  • Phone number
  • Address, State, Province, ZIP/Postal code, City
  • Cookies and Usage Data

Usage Data

We may also collect information on how the Service is accessed and used (“Usage Data”). This Usage Data may include information such as your computer’s Internet Protocol address (e.g. IP address), browser type, browser version, the pages of our Service that you visit, the time and date of your visit, the time spent on those pages, unique device identifiers and other diagnostic data.

Tracking & Cookies Data

We use cookies and similar tracking technologies to track the activity on our Service and hold certain information.

Cookies are files with small amount of data which may include an anonymous unique identifier. Cookies are sent to your browser from a website and stored on your device. Tracking technologies also used are beacons, tags, and scripts to collect and track information and to improve and analyze our Service.

You can instruct your browser to refuse all cookies or to indicate when a cookie is being sent. However, if you do not accept cookies, you may not be able to use some portions of our Service. You can learn more how to manage cookies in the Browser Cookies Guide.

Examples of Cookies we use:

  • Session Cookies. We use Session Cookies to operate our Service.
  • Preference Cookies. We use Preference Cookies to remember your preferences and various settings.
  • Security Cookies. We use Security Cookies for security purposes.

Use of Data

Force Science Institute, Ltd. uses the collected data for various purposes:

  • To provide and maintain the Service
  • To notify you about changes to our Service
  • To allow you to participate in interactive features of our Service when you choose to do so
  • To provide customer care and support
  • To provide analysis or valuable information so that we can improve the Service
  • To monitor the usage of the Service
  • To detect, prevent and address technical issues

Transfer Of Data

Your information, including Personal Data, may be transferred to — and maintained on — computers located outside of your state, province, country or other governmental jurisdiction where the data protection laws may differ than those from your jurisdiction.

If you are located outside United States and choose to provide information to us, please note that we transfer the data, including Personal Data, to United States and process it there.

Your consent to this Privacy Policy followed by your submission of such information represents your agreement to that transfer.

Force Science Institute, Ltd. will take all steps reasonably necessary to ensure that your data is treated securely and in accordance with this Privacy Policy and no transfer of your Personal Data will take place to an organization or a country unless there are adequate controls in place including the security of your data and other personal information.

Disclosure Of Data

Legal Requirements

Force Science Institute, Ltd. may disclose your Personal Data in the good faith belief that such action is necessary to:

  • To comply with a legal obligation
  • To protect and defend the rights or property of Force Science Institute, Ltd.
  • To prevent or investigate possible wrongdoing in connection with the Service
  • To protect the personal safety of users of the Service or the public
  • To protect against legal liability

Security Of Data

The security of your data is important to us, but remember that no method of transmission over the Internet, or method of electronic storage is 100% secure. While we strive to use commercially acceptable means to protect your Personal Data, we cannot guarantee its absolute security.

Service Providers

We may employ third party companies and individuals to facilitate our Service (“Service Providers”), to provide the Service on our behalf, to perform Service-related services or to assist us in analyzing how our Service is used.

These third parties have access to your Personal Data only to perform these tasks on our behalf and are obligated not to disclose or use it for any other purpose.

Analytics

We may use third-party Service Providers to monitor and analyze the use of our Service.

  • Google AnalyticsGoogle Analytics is a web analytics service offered by Google that tracks and reports website traffic. Google uses the data collected to track and monitor the use of our Service. This data is shared with other Google services. Google may use the collected data to contextualize and personalize the ads of its own advertising network.You can opt-out of having made your activity on the Service available to Google Analytics by installing the Google Analytics opt-out browser add-on. The add-on prevents the Google Analytics JavaScript (ga.js, analytics.js, and dc.js) from sharing information with Google Analytics about visits activity.For more information on the privacy practices of Google, please visit the Google Privacy & Terms web page: https://policies.google.com/privacy?hl=en

Links To Other Sites

Our Service may contain links to other sites that are not operated by us. If you click on a third party link, you will be directed to that third party’s site. We strongly advise you to review the Privacy Policy of every site you visit.

We have no control over and assume no responsibility for the content, privacy policies or practices of any third party sites or services.

Children’s Privacy

Our Service does not address anyone under the age of 18 (“Children”).

We do not knowingly collect personally identifiable information from anyone under the age of 18. If you are a parent or guardian and you are aware that your Children has provided us with Personal Data, please contact us. If we become aware that we have collected Personal Data from children without verification of parental consent, we take steps to remove that information from our servers.

Changes To This Privacy Policy

We may update our Privacy Policy from time to time. We will notify you of any changes by posting the new Privacy Policy on this page.

We will let you know via email and/or a prominent notice on our Service, prior to the change becoming effective and update the “effective date” at the top of this Privacy Policy.

You are advised to review this Privacy Policy periodically for any changes. Changes to this Privacy Policy are effective when they are posted on this page.

Contact Us

If you have any questions about this Privacy Policy, please contact us:

  • By email: [email protected]
  • By visiting this page on our website: https://www.forcescience.org/contact
  • By phone number: 866-683-1944
  • By mail: Force Science Institute, Ltd.