Forensic Psychology For Dummies (60 page)

Delving Into Investigative Psychology

As I describe in the earlier section
‘
Investigating “Offender Profiling’,
giving a detailed account of an offender’s inner psychology isn’t a lot of help to investigators (although it can be useful in guiding how to approach interviewing a suspect and sometimes helps detectives to get a feel for the sort of person they are looking for). However, some knowledge of the offender’s psychology can be useful to prosecuting lawyers in court, because they can use this insight to help the jury understand how and why a crime was committed. (Of course, similarly, the defence can use the same information to argue that the defendant couldn’t have committed the crime.)

The myths surrounding the whole idea of ‘profiling’ and its weaknesses led me to identify a branch of psychology that contributed to police investigations on a much broader front than just producing pen-pictures of unknown villains. I call this practice
investigative psychology,
which is the subject of this section.

Think of it this way. Creating a ‘profile’ of an offender requires getting details of the crime and then making some ‘if…then’ assumptions. For example, as I did in the Railway Murderer case, you may say ‘if a man has been violent to women in these crimes then the police may know someone who has been violent to women on other occasions’. This ‘if…then’ conjecture is an
inference
. You are
inferring
features of the culprit from aspects of the crime. Such inferences require an understanding of criminals and how they act, which makes it part of forensic psychology. Developing these inferences requires much more than some clever insights into the criminal mind. It draws on the many different aspects of scientific psychology that I describe in the rest of this chapter as well as other chapters in this book.

When you are making inferences about an offender you are using what is known about his actions. But as a scientist you cannot just accept the information you are given. You want it to be as reliable and valid as possible. So an important part of
investigative psychology
is developing and improving ways of getting information in investigations. (Yes, the things discussed in chapters 4 and 5 on interviewing and detecting deception are an aspect of investigative psychology).

Investigative psychology isn’t just an interesting academic pursuit (although it’s very interesting and it’s taught in many universities). It’s aimed at being useful. It therefore also explores how to help investigations, which means understanding something of how detectives think. The information from psychology that can be given is therefore more than just basic ‘offender profiling’. It covers all the ways in which psychology can contribute to investigations. The following sections give some more details of how this all works.

Following the investigative cycle

To see how psychology can contribute to all aspects of police investigations, understanding how police investigations unfold is useful. They usually follow a cycle of activity (see Figure 6-1):

1.
Information
comes to the notice of the police that a crime has been committed.
How the police get the best information through interviewing and dealing with deceit are matters that investigative psychologists can help with (as I describe in Chapters 4 and 5).

2.
Inferences
are made on the basis of that information.
This is the development by psychologists of the ‘if…then’ propositions that I discuss in the paragraph earlier in this chapter.

3.
Actions
result from these inferences that may generate more information.
Investigative psychologists can guide these actions and produce techniques the police can use like the geographical profiling systems I describe in the section ‘Locating offenders geographically’.

The cycle continues until enough information is obtained to take a culprit to court.

Despite what you see in crime fiction, psychologists very rarely get actively involved in investigations. They may pop in and give a few hints, but they contribute far less than the Crime Scene Investigation (CSI) experts who deal with fibres and fingerprints, blood splatters and all those forensic science matters.

At every stage of this cycle, psychologists can contribute:

Most information is collected through interviews with victims, witnesses or suspects. Chapters 4 and 5 show how psychologists can improve those processes.

The inference process is best thought of as an ‘if . . . then . . . so’ activity. For example, ‘
if
the criminal is moving around a particular area picking opportunities for crime
then
he’s likely to be familiar with this area when not committing crimes and
so
house-to-house inquiries in the area may be useful’. The production of ‘profiles’ are all derived from inferences.

The inferences that psychologists make about criminals are informed assumptions, not definite conclusions. They may be supported by previous research that shows, for example, the probability that a person will commit a burglary within a mile of his home. Or they may be derived from some general principles, such as that offenders who use guns have some background and experience in using guns. But these are always just possibilities, never hard and fast facts. Many circumstances can modify the reliability of these proposals (as I discuss in the later section ‘Facing the challenge of contingencies’).

The actions that the police carry out can be assisted by decision-support systems such as the process of geographical ‘profiling’ (check out the later ‘Locating offenders geographically’ section).

By
actions
I mean the pattern of activities and salient characteristics of a crime. This usage isn’t to be confused with the popular term ‘M.O.’ (that stands for
modus operandi
and literally means ‘way of doing things’). M.O. is intended to refer to the habitual way in which an offender operates. But this assumes that offenders have fixed styles of carrying out a crime and that these are different from the styles of offenders carrying out similar crimes, which is rarely the case. For example, certain aspects of all burglaries may well be similar but some rare events (like using the toilet in the burgled house) can be very unusual.