Physical Lag Times: The Use Of Deadly Force

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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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