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Criminological psychology (option): research methods, ethics and evaluation

Edexcel IAL Psychology · WPS03 Applications of Psychology

Methods for this topic (spec 6.3.1 to 6.3.4): Unit 1 and 2 methods where relevant, experiments on eyewitness memory, mock jury research, the BPS Code of Ethics and Conduct (2009) and risk management, data interpretation and evaluation.

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Experiments on eyewitness memory and mock juries

Laboratory experiments (Loftus and Palmer, 1974) manipulate an IV (verb, weapon presence, line-up instructions) and measure recall or identification under controlled conditions: cause and effect, replicable, but films and staged events lack the stakes of real crimes.
Field experiments and natural settings (Valentine and Mesout, 2009) add realism but reduce control.
Mock jury research (Ruva et al., 2007; Penrod and Cutler, 1989): participants act as jurors after watching or reading a trial. It is used because real deliberations are confidential and variables cannot be manipulated in real trials. Limitations: students rather than eligible jurors, short trials, no real consequences, often no group deliberation.
Secondary data from real trials (Bradbury and Williams, 2013): high validity, low control.

Ethics: BPS Code (2009) and risk management

The BPS Code of Ethics and Conduct (2009) has four principles: respect (informed consent, confidentiality, right to withdraw, avoiding unnecessary deception), competence, responsibility (protection from harm, debriefing) and integrity (honesty).

Risk management: researchers assess risks to participants (stress, distress at crime videos, revealing offences) and to themselves (working with offenders), and reduce them: screening out vulnerable participants, warning about content, offering support, safe locations and protocols. In criminological research: crime footage may distress victims of crime; offenders' confidentiality may conflict with disclosing new offences; studies like Valentine and Mesout must keep stress within everyday levels.

Data and evaluation

List A and List B apply. For example, invented data from 10 prisoners: weekly hours of violent games and staff aggression ratings.

Hours: 3, 7, 2, 9, 5, 6, 1, 8, 4, 10

Ratings: 4, 6, 3, 9, 4, 7, 2, 8, 5, 6

Σd² = 22.0; rs = 1 - 6 x 22.0 / (10 x 99) = 0.867. Critical value (N = 10, one-tailed, p ≤ .05) = 0.564, so significant. Show every step: examiners give credit for the Σd² column even if the final subtraction from 1 is missed.

Evaluate in the terms the specification uses: reliability, validity, generalisability, credibility, objectivity and subjectivity, ethics and practical application.

Worked example

A researcher wants to test whether a weapon reduces identification accuracy. Design a laboratory experiment and identify one ethical issue.

IV: video of a robber holding a knife or a mobile phone (independent groups, random allocation). DV: correct identification from a six-person line-up.
Controls: same actor, lighting, duration and line-up for both groups.
Ethics: the knife video could distress some participants, so warn them about the content, gain informed consent, allow withdrawal and debrief.

Answer: Weapon v phone video, line-up DV, with warnings and debriefing.

Key idea: Methods: lab experiments on eyewitness memory (control, low ecological validity); mock juries (manipulate variables ethically, but no real consequences); real trial data (valid but correlational). BPS Code (2009): respect, competence, responsibility, integrity; risk management for participants and researchers. Show all workings in calculations.

Check yourself

Why are mock juries used instead of real juries?
- Real deliberations are confidential and variables cannot be manipulated in real trials
- Mock juries are more realistic
- Real juries never reach verdicts
- Mock juries are always made up of lawyers
Show answer
Real deliberations are confidential and variables cannot be manipulated in real trials. Access and control.
Which is one of the four principles of the BPS Code of Ethics and Conduct (2009)?
- Reliability
- Validity
- Respect
- Objectivity
Show answer
Respect. Respect, competence, responsibility, integrity.
Which is an example of risk management in eyewitness research?
- Warning participants that a video shows violence and screening out victims of crime
- Using a larger sample
- Using a one-tailed hypothesis
- Showing the video twice
Show answer
Warning participants that a video shows violence and screening out victims of crime. Reducing risk of distress.
For the invented prisoner data, Σd² = 22.0 with N = 10. Calculate rs to 3 decimal places.
Show answer
0.867. 1 - 6 x 22.0 / 990 = 0.867.
Which is a strength of laboratory experiments on eyewitness memory?
- They have high ecological validity
- Control of variables allows cause and effect to be established
- Participants experience real fear
- They use real trial verdicts
Show answer
Control of variables allows cause and effect to be established. Control.
A study of eyewitness memory used only university students. Which improvement best increases generalisability?
- Use more students from the same course
- Use a one-tailed test
- Repeat the study with the same participants
- Recruit a stratified sample of adults of different ages and backgrounds from the community
Show answer
Recruit a stratified sample of adults of different ages and backgrounds from the community. A wider, representative sample.
Explain one weakness of mock jury research.
Show answer
Mock jurors know their verdict has no real consequences for the defendant and often watch a shortened trial, so their decisions may differ from real jurors, giving low ecological validity.. Name the difference from real juries and its effect.

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Last updated 8 November 2026. Spotted a mistake? Tell us.