researchers have suggested that the dismantling of
state mental hospitals, the changing mentally ill pop-
ulation, the tightening of requirements for receiving
mental health support, and the offering of limited psy-
chological services are possible explanations.
The police are receiving education and training in
the handling of people with mental illness. They rec-
ognize that mental illness is not a crime and that
people having mental illness live in their communi-
ties, have professional vocations, and call for police
services. The police also know that empirical investi-
gations have found a link between mental illness and
criminal behavior. For example, persons who suffer
from bipolar disorder or schizophrenia are more likely
to express antisocial behaviors that society criminal-
izes. Most mentally ill offenders are under the influ-
ence of alcohol or drugs when they commit crimes.
There is some increased risk of mentally ill individu-
als becoming violent.
Although people who have a mental illness may
commit a crime, be a victim of crime, or report a
crime, police responses to encounters with them have
improved with training. Police personnel, psycholo-
gists, and other mental health professionals have
developed training curricula that include topics such
as symptomatology of mental conditions, nonarrest
and arrest options, and community police responses.
They have developed and made available model
police policies for contacts with people with mental
illness. These policies have helped police administra-
tors standardize the nature of their departments’
response while giving the police flexibility to meet the
needs of people with mental illness.Conducting Criminal Investigations. Psychologists
have studied the procedures and tactics used by the
police in criminal investigations. They have produced
psychological knowledge and have helped the police
apply it to criminal investigation techniques such as
eyewitness identification. For example, a police detec-
tive has a crime suspect and asks an eyewitness to
identify him or her by viewing photos. The detective
shows the eyewitness eight photos one at a time
(sequentially) rather than all at the same time (simul-
taneously) to reduce the chances of misidentification
caused by the eyewitness comparing photos and try-
ing to decide which one looks most like the suspect.
Chances of misidentification are less when the detec-
tive does not know the actual identity of the suspect,
tells the eyewitness that the suspect’s photo may ormay not be present, gives the eyewitness no feedback
during or after the identification procedure, and asks
the eyewitness about his or her level of confidence in
the identification.
What psychologists have known about police inter-
rogation tactics is that some of them lead to false con-
fessions. For example, a police detective has a suspect
of a crime and interrogates him or her for several
hours. An interrogation is a stressful experience for
the suspect. In a state of high stress, some suspects are
highly suggestible and might come to believe that the
accusations made by the detective are true. Other sus-
pects may confess if the detective threatens punish-
ment or makes promises during the interrogation—
even if the suspect knows that he or she is innocent. In
other cases, the desire for attention or fame, especially
in a highly publicized crime, might motivate the sus-
pect to confess despite having done nothing wrong.
Police detection of the lies told by suspects during
interrogation has received considerable research
attention by psychologists. The police know that
uncontrollable physiological arousal often accompa-
nies a suspect’s lying. For example, a police detective
has a suspect of a crime and uses the polygraph tech-
nique (or device) in interrogation. The polygraph
examiner asks the suspect several non-crime-related
questions that generate emotional responses (e.g.,
about past behaviors) and several crime-related ques-
tions. Both provoke physiological responses, but the
crime-related questions provoke more physiological
responses than the non-crime-related (or control)
ones, which suggests that the suspect is guilty. Most
courts do not accept polygraph results as evidence.
Psychological research has suggested that the rate of
accurately detecting deception is low and the rate of
false positives is high. The police, however, continue
to use the technique with others and try to convince
suspects that they cannot beat the device and that they
should admit the fact of having committed a crime.
Hypnosis is another investigative technique avail-
able to the police. Usually psychologists, psychia-
trists, or trained forensic hypnotists conduct interviews
using hypnosis. They use the technique mostly to
obtain information from eyewitnesses or victims and
rarely to obtain information from suspects. There is
little empirical evidence to support the belief that hyp-
nosis elicits reliable memories.
Criminal profiling is a set of investigative tech-
niques used to identify the characteristics of suspects
most likely to have committed a crime. For example,582 ———Police PsychologyP-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 582