Physical Lag Times: The Use Of Deadly Force

[brownie]

Interesting read----------------

Physical Lag Times and Their Impact On The Use Deadly
Force

Previously published in The Tactical Edge, Spring 1995

By: Captain Michael R. Hillmann, Los Angeles Police Department

INTRODUCTION

Routinely, law enforcement supervisors, administrators, use of force review
boards and civilian jurors are required to evaluate police officers and their
application of deadly force. Oftentimes, from an evaluator's perspective, the
task of deciding whether an officer acted appropriately or not is a difficult one
at best. In all cases, individual state of mind of the officer serves as the
foundation for determining "appropriateness of actions," while the law and
policy represent key precepts that guide police officers in making their
decision to shoot or not shoot. Add to this decision-making criteria, human
factors, such as, perception time, brain lag and reaction time and the problem
of incident evaluation becomes considerably more complex.

It is recognized that the time lags involving perception time, brain lag and
reaction time are not an excuse for improper tactics or poor judgment. Police
officers must avoid, when possible, placing themselves in positions of jeopardy
where they are left with no other alternatives than to shoot. However, in order
to balance "no action" with "the duty to perform," one must remember that
police officers are trained and practiced to protect the public and are
expected to be proactive in pursuit of their duty. Therefore, police officers
may find themselves in perilous positions where the decision to utilize "deadly
force" is predicated on the circumstances created by the suspect, "it is the
suspect who initiates the action and the officer who responds"4 .

It is the intent of this article to focus on the physical time lags involving,
perception time, brain lag, and reaction time, their definitions, and how they
affect a police officer's decision to utilize deadly force.

STATEMENT OF THE PROBLEM

Occasionally, conflicts will arise during post incident analysis of incidents
involving the use of deadly force, between an officer's recollection, statements
and certain physical evidence. Please consider the following situations:

1. "The police officer shot an assault with a deadly weapon (ADW) suspect
after he made a movement consistent with arming himself. The suspect was
determined not to have a gun (after the fact). At the time however, the officer
reasonably believed the suspect was armed with a gun and about to inflict
great bodily injury or death upon him".

2. "The officer shot an assault with a deadly weapon (ADW) suspect, who
moments prior, was observed to be armed with a pistol. After discarding the
pistol, the suspect ran a few feet from the officer's position toward an
unsecured area. At the time the officer believed an additional firearm could
have been retrieved and utilized against him or other officers present".

3. "The officer stated he discharged his weapon when the suspect's front chest
was facing him, however, the evidence indicated the bullet entered the back of
suspect's upper body".

PHYSICAL TIME LAG STUDIES

Before an analysis of the above situations can take place, certain parameters
must be established in order to understand the impact of "physical time lags"
affecting police officers. Therefore, for the purpose of discussion only, assume
the following facts to be true: (1) Police officers generally attempt to utilize
proper tactics, are trained in the law, deadly force policy and are proficient in
the use of their firearm; (2) Police officers are lawfully entitled to be where
they are under the circumstances and (3) Police officers are honest and
forthright in reporting their observations and actions.

Consider a Department of Transportation, Federal Aviation Administration,
Civil Aeromedical Institute Physiological Operations study conducted
regarding collision avoidance: "Inherent in the body are three physical time lags
which are critical in high speed flight.

Perception Time (0.1 second)

The time required for an impulse to be generated in the eye and
transmitted to the brain.

Brain Lag (0.1 second or more)

The time required for a decision.

Reaction Time (0.4 to 0.8 second)

The time required for an impulse to travel from brain to hand, feet etc.
which triggers some physical reaction to the original eye stimulus. It is
not unusual to take up to five seconds before the aircraft begins evasive
action" (considering collision avoidance)".

There have been other studies regarding physical time lags, specifically relating
to driver training. For example, the Los Angeles Police Department's Driver
ing Unit Lesson Plan2. has defined "reaction time" as follows:

"The time that elapses between the driver's perception/decision and the
time the brakes are applied or the steering wheel turned. The average
human reaction time, under these circumstances is 0.75 of a second".

It is significant to note, the conclusions of both independent studies arrived at
an average reaction time of between 0.75 to 0.8 of a second.

The Federal Aviation Administration, "High Speed Flight" physical time lag
study in particular, is applicable to a law enforcement use of force setting. For
example, a police officer, believing he is confronted with a life-threatening
situation, waits to see the suspect's gun before he draws and discharges his
service pistol. Under these circumstances, if we apply the above physical time
lags we would see that the officer would probably be shot before he could
remove his weapon from his holster. In this specific case, the officer's time for
reaction starts after the suspect's weapon is observed. The suspect, already
committed to action, is able to draw and shoot before the officer can
effectively respond. The officer's reactive measures e.g., "return fire," could be
as much as 1.0 second or more behind the suspect's discharge of two rounds.

Whether a police officer's pistol is holstered or unholstered makes little
difference in the above situation. When the officer's pistol is unholstered and in
a properly sighted, shooting position, we may see a slight reduction in reaction
time. Unfortunately, the best that can be expected is a "tie" between the officer
and the suspect. Considering both the suspect and police officer would be
shooting at each other, in all probability both will be shot.

Next, factor into the above situation the following: The officer, (1) must be
accurate in target acquisition, (2) is only allowed to continue applying deadly
force long enough to stop the threat, (3) must continuously assess the threat,
then (4) consciously decide to stop shooting when the threat stops. This entire
process involves all of the aforementioned physical time lags of perception
time, brain lag and reaction time in order to accomplish. Simply stated, the
officer perceives that the threat has been stopped, transmits that observation
to the brain, decides to cease shooting, then physically must stop pulling the
trigger.

THE LAW

A police officer is not required by law or policy to wait to see a gun before he
discharges his firearm in self-defense or defense of others when he reasonably
believes, based upon the circumstances, that he is facing an imminent threat of
great bodily injury or death. Whether or not it is determined after the fact that
the suspect actually was reaching for a gun, does not invalidate the officer's
actions based upon the reasonable belief that he was about to be shot and his
personal knowledge of the physical time lags involved.

In recent years, the problems associated with use of force decisions by police
officers have not gone unnoticed by the courts. It is acknowledged that Police
officers are forced to be able to quickly assess situations and make split
second decisions involving the use of deadly force as reflected in the U.S.
Supreme Court case, Graham v. Connor 3. :

"The reasonableness of a particular use of force must be judged from the
perspective of a reasonable officer on the scene and its calculus must
embody an allowance for the fact that police officers are often forced to
make split-second decisions about the amount of force necessary in a
particular situation".

.

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OTHER "TIME" FACTORS

In the course and scope of employment as a policeOTH officer, supervisor and
manager, the author has had the opportunity to review several hundred officer
involved shooting situations for training, officer safety, administrative use of
force review boards, courtroom presentations and internal discipline.
Following these examinations involving hundreds of investigative hours,
personal experience, evaluation of suspects actions and interviews of
"shooting" police officers, it has been the author's observation that:

1. A suspect armed with a pistol, secreted in his waistband, can draw and
fire at least two shots within 1.0 to 1.5 seconds.

2. Approximately 90% of all officer involved shooting incidents take place
within a three-second-time period.

POST INCIDENT ANALYSIS

As mentioned initially, during post-incident analysis, oftentimes conflicts arise
between an officer's statement and the actual evidence. Please consider the
following additional scenarios and explanations.

1. An officer stated during the officer involved shooting interview he
discharged his firearm in defense of himself when the suspect was facing him.
The forensic evidence indicated however, the bullet track was posterior to
anterior. Under the specific circumstances, perception time, brain lag and
reaction time of the officer, combined with continued movement of the target
(suspect), may have accounted for the inconsistency between the officer's
initial statement and the actual evidence.

2. A suspect believed to be armed with a handgun is chased by a police
officer. The suspect stops, turns to his right and partially faces the officer. The
suspect removes what appears to be a handgun from his waist, extends his
right arm, while turning to his right. He then makes a movement consistent with
assuming a shooting position. The police officer, in pursuit, perceives the threat
(0.1 second), stops, assesses that he is in imminent danger of being shot,
decides on the appropriate use of force and makes the decision to shoot (0.6
to 0.8 or more seconds). At this point, the suspect is continuing to move, turn,
bend, squat, run, climb, throw, stop etc.. In the beat of a heart, the officer
makes the decision to shoot, based upon the belief of imminent threat to life.
He acquires the target, aligns his front and rear sight and squeezes the trigger
twice in rapid succession (1.0 second or more). The suspect falls to the
ground shot in the back. Under the circumstances, the officer's perception of
the threat, decision to shoot plus actual shooting time, required at least 1.0
second or more to implement. During this period of time the officer observed
certain facts and decided on a course of action while the suspect's movement
continued. In closer examination, at the time the officer actually commenced
shooting one would probably find that the suspect was turning back, toward
his left when the bullet(s) impacted . During the post incident, officer interview
however, the officer may have recalled he discharged his weapon while the
suspect was facing him, when in reality, the suspect actually was in the process
of turning away from him.

This discrepancy does not mean the officer was being untruthful at the time of
the interview. Quite the contrary, the physical time lags affecting the officer, his
recall of the suspect's position at the moment he decided to shoot combined
with the continuous movement of the suspect after he started shooting, may
have accounted for the discrepancy between the officer's belief as to the
position of the suspect when he shot and the actual physical evidence. In other
words, the officer's reaction lagged behind the actions of the suspect.

It is also recognized that many factors can affect the above examples; tactics,
positioning, movement of the officer, accuracy and availability of cover, etc..
The point is, the physical time lags (perception time, brain lag and reaction
time) combined with the movement of both officer and target must be equally
considered prior to formulating opinions of what occurred.

As indicated previously, "crisis decisions," i.e., the use of deadly force, require
time (perception, brain lag and reaction time) in order to implement. Just as it
takes time for the police officer to perceive, decide and react to an impending
threat, it also takes time for the officer to perceive, decide and actually stop
his reactive measures. It has been the author's experience to note that criticism
has occasionally arisen regarding an "alleged" excessive number of rounds
being fired by a single "shooting officer".

An officer who is shooting to stop the actions of the suspect is required to
continuously assess the threat throughout the event, and when, in his opinion
the threat is stopped, must "de-escalate" his force. Under these circumstances,
the sequence of de-escalation requires time to implement. It is not unusual to
find that an officer may have attempted to cease fire after 2 to 4 shots
(depending upon the weapon) but, in reality discharged 10 shots or more. In
the final analysis, this alleged "excessive" number of rounds discharged may
not have been excessive at all, and may be attributed to the physical time lags
involved in the officer's deciding to de-escalate response. In short, the officer
may have been unable to immediately discontinue shooting after the initial 2 to
4 shots, due to the perception time, brain lag and reaction time required to
stop the action.

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PHYSICAL TIME LAGS AND DISTANCE

A suspect's proximity from a deadly weapon (e.g., arms reach) and a police
officer's distance from a suspect (lunging distance) coupled with the physical
time lags required for defensive reaction, can impact the decision to utilize
deadly force. Under specific conditions, a police officer may have no other
tactical options (e.g., cover, concealment, position etc.) and the threat of
serious bodily injury is "reasonably" present. The officer may be forced into a
deadly force situation in order to stop the suspect (e.g., movement towards
arming himself with a weapon). Officers are not expected to allow suspects to
arm themselves and then set about physically engaging and disarming them.
The law and use of force policies do not require officers to use the same or
lesser amounts of force to overcome a suspect's resistance. Police officers are
required to utilize that amount of force which is "reasonable" to overcome
resistance. "Grappling" with an armed suspect not only increases the risk to
the police officer, but tends to exacerbate and escalate the situation.

SUMMARY OF TECHNICAL AND TACTICAL POINTS:

1. The components of physical time lags are:

* Perception time 0.1 second

* Brain lag 0.1 second or more

* Reaction time 0.4 to 0.8 seconds

2. The sum total of physical time lags (perception time, brain lag and reaction
time) is generally between 0.75 and 1.0 second.

3. An armed subject with a firearm secreted in his waistband can draw and
discharge a minimum of 2 shots within 1.0 to 1.5 seconds.

4. Physical time lags, combined with continuous movement of a suspect, can
account for discrepancies between an officer's account of events and the
actual post-incident evidence.

5. A police officer's perception time, brain lag and reaction time all begin after
the suspect's actions are already underway.

6. A police officer's decision to de-escalate the use of deadly force is subject
to the same physical time lags as the decision to use deadly force.

7. Proximity of a suspect from a potential weapon (distance of a police officer
from the suspect), coupled with physical time lags, can effect the decision to
utilize deadly force.

8. The existence of physical time lags, perception time, brain lag and reaction
time does not justify the use of poor or inappropriate tactics.

9. Under life-threatening conditions, waiting to see a suspect's gun before a
police officer utilizes deadly force can result in injury and/or death to the
officer.

CONCLUSION

In conclusion, the post incident analysis of an officer involved shooting is
complex at best. It is hoped that those who sit in review of police officers’
actions consider the "fast moving circumstances" of the situation, the impact of
physical time lags and the officer's overall "state of mind" at the moment he
decided to shoot. The issues involving "physical time lags" are present, to
some degree, in most officer-involved shooting situations. Additionally, it is
this author's opinion that in some cases, these time lags have been given little
consideration when analyzing the totality of the involved police officer's
actions. The most stressful, emotionally impacting and permanent decision a
police officer can ever make is the decision to utilize deadly force. The best
those of us sitting in judgment can do is understand the totality of the
circumstances, the concept of physical time lags and their impact on the use of
deadly force.

About the Author:

Captain Michael Hillmann is the commanding officer of LAPD’s West
Los Angeles Area. His 33 years with the LAPD include assignments to
patrol, Anti-Terrorist Division, and the Special Weapons and Tactics
(SWAT) team. He has written articles for a wide variety of publications
and presented in-depth courses on tactics and emergency response to law
enforcement, the military, and private industry. He is widely regarded as
one of the premier experts in emergency response and tactics.

End notes:

1. Department of Transportation, Federal Aviation Administration, Civil
Aeromedical institute Physiological Operations, Physiological ing -
High Speed Flight, p. 24, January 1972.

2. Los Angeles Police Department, ing Division, Driver ing Unit,
Instructor Lesson Plan, "Vehicle Operation Factors", The Human Factor -
Reaction Time, C-1.

3. United States Supreme Court, Graham v. Connor (490 U.S. 386 - 1989).

4 Lt. Joe Callanan, (LASD retired) The Tactical Edge Magazine, Use of
Force After The Rodney King Incident, p.17, Fall 1992

[pitor]

Good article. But sadly civilians are not afforded the same level of review of expert panels. Nor is this perception time lags even factored in civilian defensive use of deadly force.

[BlackKnight]

I'm certified as an expert here in N.J. in the use of force.
I've testified many times in front of a grand jury and had to explain action vs reaction. I've been able to do a pretty good job without getting in the science of it. We haven't had a need for that yet. This does a good job of explaining things as well.
I use Force Science News as a resource. This is good too. I will print it out and use it if necessary.
Thanks for posting

[brownie]

Welcome BlackKnight, glad someone can make use of the information. I find it relevant to understand and be able to articulate this type of information from the scientific community to dispel the myths that abound out there.

I also get the FS newsletters, worth reading all of their testing and conclusions.