Bottom-up Approach Revision Notes for AQA A-Level Psychology

Bottom-up Approach

Introduction to investigative psychology

The bottom-up approach is a method used by forensic psychologists that analyses data from previous, similar crimes to create an objective profile of a possible offender. This approach was developed in the UK by David Canter, who wanted to create a more scientific method that relied on statistical analysis rather than intuition.

Investigative psychology forms the foundation of the bottom-up approach. This method attempts to describe offender behaviour and develop understanding of their actions through systematic analysis. The approach uses statistical techniques to make it more objective than intuitive methods.

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The bottom-up approach represents a significant shift from earlier profiling methods by emphasising scientific rigour and statistical analysis over subjective interpretation and intuition.

Core assumptions of investigative psychology

The bottom-up approach is built on five key assumptions about criminal behaviour:

Interpersonal coherence - There is consistency across situations in how offenders behave. An aggressive person is more likely to commit aggressive crimes, meaning their everyday behaviour patterns will be reflected in their criminal actions.
Time and place - The timing and location of crimes provide valuable clues about the perpetrator's living habits or work patterns. These factors can reveal where an offender might live or work.
Criminal characteristics - Placing criminals into categories helps police investigations. Different types of offenders show distinct behavioural patterns that can be identified and classified.
Criminal career - Consideration of how experienced offenders are and how their crime patterns might develop over time. More experienced criminals may show different patterns compared to first-time offenders.
Forensic awareness - Offenders who show awareness of forensic investigation techniques (such as cleaning crime scenes) have likely committed crimes before and been through the criminal justice system.

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These five assumptions work together to create a comprehensive framework for understanding criminal behaviour. Understanding interpersonal coherence is particularly crucial as it links an offender's everyday personality to their criminal actions.

Geographical profiling

Geographical profiling represents a key component of the bottom-up approach. This technique analyses the locations of connected crimes to determine the probable area where an offender lives. The method focuses on location and timing aspects, based on the assumption that these factors reveal important information about the offender's living habits.

Four main principles of geographical profiling

Locatedness - Crime locations reveal information about the offender. Multiple locations are particularly valuable for creating accurate profiles. Key locations include where victims are initially encountered, where attacks occur, where victims are killed, and where bodies are disposed of.
Systematic crime location choice - Offenders do not choose locations randomly. Familiarity with areas is important, meaning chosen locations deserve careful consideration as they reflect the offender's geographical knowledge.
Centrality - This principle identifies two types of offenders:
- Commuters - travel to commit crimes but typically in areas somewhat familiar to them
- Marauders - commit crimes close to their home base, meaning crimes tend to cluster around where they live
Comparative case analysis - Other similar crimes should be considered as potentially committed by the same offender. The more crimes linked to one person, the greater the accuracy of geographical profiling becomes.

When these principles are applied to crime locations, they help police narrow down suspect pools and focus resources on specific geographical areas for door-to-door enquiries and patrols.

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The distinction between commuters and marauders is particularly important for investigations, as it fundamentally changes where police should focus their search efforts and resources.

Case study: John Duffy - the Railway Rapist

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Worked Example: The Railway Rapist Case Study

Researcher: Canter and Heritage
Year: 1990
Case: John Duffy (Railway Rapist)

Background: From 1982 to 1985, a series of rapes occurred near railway stations in south-east England. The perpetrators were initially nicknamed the Railway Rapists, but when three women were killed, they became known as the Railway Killers.

Procedure: Police brought in Dr David Canter, a criminal profiler, to help with the investigation. Evidence suggested one perpetrator worked alone, so Canter applied his profiling theory to create an offender profile. The profile included both personal characteristics and geographical information based on crime locations.

Key Findings:

Canter's profile proved highly accurate - 12 of the 17 suggested characteristics were correct
The geographical information was particularly valuable, helping to focus the investigation
Following Canter's profile, John Duffy was arrested
Although he initially claimed he had not worked alone, it was not until 1997 that he revealed his accomplice's name, leading to David Mulcahy's arrest

Outcome:

Duffy was charged with 11 rapes and 2 murders
Mulcahy was charged with 7 rapes and 3 murders
Both will never be released from prison

Evaluation of the Case:

Strengths: Canter's profile was highly accurate with most characteristics being correct; the geographical information proved particularly valuable for focusing the investigation
Weaknesses: This represents a single case study, limiting its value for providing evidence that this profiling method works universally

Research evidence

Several studies have examined the effectiveness of the bottom-up approach:

Copson (1995) surveyed 184 US police officers and found that 82% found top-down profiling useful, while 90% said they would use it again. This suggests the approach is well-regarded by practitioners.

Lundrigan and Canter (2001) analysed 120 murder cases and discovered that offenders' home bases were consistently located in the centre of their crime scene patterns, providing strong support for geographical profiling principles.

Canter and Heritage (1990) examined 66 sexual assault cases using 'Smallest Space Analysis' (an investigative psychology technique) and identified clear behavioural patterns, supporting the bottom-up approach's effectiveness.

However, Snook et al. (2008) reviewed criminal profiling evidence and concluded that the belief in profiling's ability to predict criminal characteristics was largely unsupported, based more on anecdotal evidence than scientific backing.

Pinizzotto (1984) found that only 17% of 192 criminal profile requests actually helped identify suspects, though 77% of respondents said the profiles helped them focus their investigations.

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The research evidence presents a mixed picture - while police practitioners find profiling useful for focusing investigations, scientific studies question its effectiveness in actually identifying suspects. This highlights the importance of understanding what profiling can and cannot achieve.

Evaluation of the bottom-up approach

Strengths

Scientific foundation - The approach is based heavily on research and statistical analysis, making it more scientific than intuitive top-down methods. Statistical techniques remove profiler intuition from the process, arguably making it more reliable.
Practical applications - Geographical profiling helps locate offenders across many different crime types. It can identify likely home locations of burglars, as they often concentrate crimes in familiar areas near where they live.
Police acceptance - Research shows most police officers find profiling useful and would use it again, suggesting practical value in investigations.

Weaknesses

Limited focus - While geographical information is important for identifying offenders, other psychological characteristics also need consideration. Focusing primarily on location might miss important behavioural information.
Data requirements - The technique requires statistical information from previous crimes, which is not always available. Incomplete or inaccurate crime data can affect the method's reliability.
Mixed research support - Studies show conflicting results about profiling effectiveness. Some research suggests limited practical value in actually identifying suspects, while other studies show more positive outcomes.
Measurement difficulties - Because criminal profiling is often used alongside other police work, it can be difficult to establish exactly how much it contributes to solving cases, making effectiveness assessment challenging.

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The bottom-up approach's greatest strength lies in its scientific foundation, but investigators must be aware of its limitations, particularly the heavy reliance on quality data and the mixed evidence for its effectiveness in actually identifying suspects.

Summary

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Key Points to Remember:

The bottom-up approach uses statistical analysis of crime data to create objective offender profiles, developed by David Canter in the UK
Five key assumptions underpin investigative psychology: interpersonal coherence, time and place factors, criminal characteristics, criminal career progression, and forensic awareness
Geographical profiling focuses on crime locations using four principles: locatedness, systematic location choice, centrality (commuters vs marauders), and comparative case analysis
The John Duffy case demonstrates successful practical application, with Canter's profile proving highly accurate in identifying the Railway Rapist
Research evidence shows mixed results - police find it useful, but scientific studies question its effectiveness in actually identifying suspects

Bottom-up Approach (AQA A-Level Psychology): Revision Notes