Incident Amnesia: The Physiological Basis and the Implications
of Memory Loss During Extreme Survival Stress Situations"
Lt. Col. Dave Grossman & Bruce K. Siddle
Firearms Instructor: The Official Journal of the International
Association of Law Enforcement Firearms Instructors
Issue 31 / Aug 2001
law enforcement officer is constantly required to move to
the most traumatic and stressful situations in our society,
to respond instantly and appropriately in these critical
incidents, and then to accurately remember and report everything
that occurred. Unfortunately, by their very nature, traumatic
situations will inevitably result in memory impairment,
which is referred to here as "critical incident amnesia."
The greater the stress, the greater the potential will be
for these memory problems to occur.
who encounter an extremely stressful situation will consistently
exhibit difficulty in transferring information into long
term memory. Particular memory related phenomenon in traumatic
During the actual incident there is usually a "sensory
overload" combined with a "fixation" on some particular
aspect of the critical incident, often to the exclusion
of all else.
after the incident, "post-incident amnesia" will often
result in a failure to remember the majority of the information
observed in the incident.
After a healthy night's sleep there is usually a "memory
recovery" which will result in the remembering the majority
of what occurred, and this memory is probably the most
Within 72 hours the final and most complete form of memory
will occur, but it will be at least partially "reconstructed"
(and therefore somewhat "contaminated") after the inevitable
process of integrating available information from all
other sources (media).
incident amnesia is one of the ultimate horrors in a law
enforcement environment. Failure to understand and address
this problem can cause grave injustices. Memory failure
in law enforcement officers, victims, and witnesses can
result in a failure to convict or even to apprehend the
guilty, or it can result in the prosecution and even the
conviction of the innocent. This article will outline the
aspects of critical incident amnesia, and will then address
the implications and applications of critical incident amnesia
to the law enforcement community.
Influences Before The Critical Incident....All individuals
have a set of schemas, inferences, and expectations that
they bring into a situation, and which have significant
potential to distort their memory of a critical incident.
and Perceptual Distortion.....Since memory is a product
of perception, it is clear that memory can be disrupted
when perception becomes disrupted.
Amnesia.....If we do not attend to something it is
generally lost to memory (Cherry, 1953; Moray, 1959).
Intense fixation of attention on a particular aspect of
a critical incident can cause vivid memories in some areas,
but by definition this focused attending in one area will
cause a reduction in attending (and thus to memory) in
all other areas.
Recovery......After a critical incident much of the
information may still be in the brain but it has not been
processed in such a manner that it can be retrieved.
Reconstruction.....Inevitably, an individual who has
encountered a critical incident will seek information
from outside sources in order to make sense out of what
has occurred. In many cases this process of exchanging
information will provide "retrieval cues" which will aid
in the retrieval of information.
and Implications to Law Enforcement.......The implications
of critical incident amnesia on law enforcement are profound,
and it is vital that procedures be established which will
ensure that the most accurate and most complete memories
are protected and preserved as a part of standard procedures.
overall application of a scientific understanding of memory
processes in a law enforcement environment has potential
for tremendous payoff.
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