A2 - G543 Studies - MAKING A CASE.

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Aim: To test police officers' ability to detect lies & truths when interviewing suspects.

Method: Field experiment; Correlation.

Sample: 99 kent P/O | 78 det. | 4 traffic officers | 9 Unis. | 24 f, 75 m. Mean age - 34.3

Procedure: PPs had to judge the truthfulness of people in real police interviews, PPs filled out a Q/aire about exp w detecting lies/liars, then watched clips of 14 suspects. Clips were paired up w/ evidence, varying from 6 - 145 seconds, total of 54. After each clip, they chose truth/lie & said how confident they were in their answer. They were asked to list the cues used in lie detecting.

Findings: Mean lie accuracy - 66.2%                                                                                                       Mean truth accuracy - 63.6%

Experience in interviewing correlated with truth and lie accuracy.                                                 Most freq. cue = gaze, movements, vagueness, contradictions, fidgeting,

Conclusions: Good lie detectors rely more on story cues than physical ones. The more experience an officer has = better at lie detecting.

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Aim: To test Cognitive Interview in the field.

Method: Field experiment - interviewing real witnesses by serving police det.

Sample: 16 det. from Robbery Division of Dade County, FL w a min. of 5 yrs exp.

Procedure: In the first phase, 88 interviews were recorded over 4 months, relating to bag snatches. They were then split in 2 groups, with one being trained in CI. Training prog. was 4 x 60 min sessions, 7 completed it. Over the next 7 months, more interviews were recorded by exp and control group, then analaysed by a team of blind researchers from Uni of California.

Findings: The 7 trained det. gathered 47% more info after being trained, and acquired 67% more info than untrained det. Both groups got approx. 85% accurate statements. Accuracy measured via corrobating info with another source. 94% of statements were corroborated.

Conclusions: Support for effectiveness of CI in field was found. More info retained, no loss of accuracy & a minimal increase in duration time. Results in field mirrored those in the lab, adding ecological validity. CI has been since applied to clinical settings to develop medical histories.

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Bottom Up Typology

Aim: Test reliability of organised/disorganised typologies.

Method: Content analysis using psychometric method of multi-dimensional scaling.

Procedure: 100 cases assessed to find out if features hypothesised to belong to each typology would be consistent and distincively different to each other. All cases were from USA, the third crime of a serial killer was the one analysed. The Crime Classification Manual was used to classify the crimes in a typology.

Findings: Twice as many disorganised scene traits were ID'd, suggesting they're more common, or easier to identify and capture disorganised offenders. Only two crime scene behaviours significantly co-occured in the organised typologies:   Body concealed - 70%                                                                                                     Sexual activity - 75%                                                                                                                                               Smallest space analysis failed to clearly seperate org/disorg variables.

Conclusion: No clear distincition between the two types, all kills have organised element to them.

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- Offers an approach to interrogate techniques, and insight in how to secure confessions from unwilling suspects.


- Study is highly unethical. Abuses position of officers, mistreats suspects and can lead to forced and coerced confessions. Interrogators may miss the correct offender due to being blinded by th10. GUDJOHNNSON & MACKEITH - INTERVIEWING SUSPECTS.is etc.

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- Uses field experiments, which gives ecological validity - this improves the usefulness of the study and it's practical applications to real interviews.

- Uses trained det. with ecxperience, reduces ext variables such as individual differences.

- Standardised procedure e.g. the training, making the study replicable and reliable.

- Quantitative data, easy to compare and analyse. Also, objective. (Strengthened by blind team) which eliminated researcher bias.


- Sampe is small, ethnocentric and androcentric. This limits generalisability of findings to TPs.

- Training is time consuming and effort consuming, reducing replicability ease.

- Risk of demand characteristics, as det. want to be viewed in an SDB manner. Also observor effect od recording device as ext. variable, reducing validity.

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Aim: Provide support for 'weapon focus' effect when witnessing a crime.

Method: Lab experiment.

Sample: 36 students @ Uni of Washington, 18-31 yrs old. Half recruited through ad agency, paid for PP and rest got extra credit in their psychology classes.

Procedure: Experimental and control condition. Each group saw a set of 18mm slides of people moving through a taco time queue, the IV is the object person B (second person in line) pulls out: a cheque or a gun. All slides were shown for 1.5 seconds, the DV was measured via a 20 item multiple choice questionnaire. PPs were also given a line-up of 12 mug shots in random sequences & were asked to identify person B & rate the confidence of their ID on a scale of 1-6.

Findings: Chance performance on photo line-up was 8.5%.                                                                       Control group - 38.9% correct, 7 people.                                                                                   Experimental - 11% correct, 2 people.

Eye fixation data was 3.72 for gun, compared to 2.44 for cheque.                                             

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- Lab experiment = high level of control & standardisation. As this reduces ext. variables, it improves validity and the consistency improves reliability.

- Multiple ways to measure the DV, for concurrency and this strengthens validity of study.

- Useful applications for court, and to improve witness testimonies.


- Sample was all psychology students, with motives, this may mean ext variables such as SDB and DC were in play. Making the results in valid.

- As its in lab conditions, it lacks ecological validity.

- Unethical, as PPs were decieved about the aim. This makes the study harder to replicate, decreasing its reliability.

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- Sample was fairly large, with different ranks of officers, both genders and differing ages. This is representative of TP.

- Useful applications in identifying best lie detectors, can be used in real world.

- Field experiment provies ecological validity, correlation is quanitfied so easy to compare and analyse. Also, objective and scientific.


- No control grop to comapre difference in skill to ordinary people/officers.

- Do not interview suspects themselves, can lack ecological validity and produce ext. variables.

- Ethnocentrism limits the generalisiblity of the findings.

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- Based on a real case, so there's high ecological validity and reliability. Quasi conditions, only way to study false confessions ethically. 

- A lot of datal, both qualitative and quantitative over a longitudinal period of time.

- Identity was withdrawn, protecting FC and the ethical guidelines.

- Provides support for reliabiliy of GSS as a measure.

- Very useful, with practical applications.


- As it's a case study, sample is very small and restricted. Therefore can not be generalised to all situations.

- Extraneous variables such as individual differences could make the case an anamoly.

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Aim:  Get a confession from an interrrogation.

1. Suspect told directly they're believed to be guilty of the offence.                                   

2. Suspect is offered chance to shift blame, by offering justifications for the crime. Show empathy.

3. Suspect is blocked from ever verbally denying guilty by interrogator.

4. Ignore suspects attempts to explain why they could not be guilty for the offence.

5. Use eye contact and names, to establish close atmosphere for them to admit guilt.

6. When suspect quitens, offer alternatives. If suspect cries, infer guilt for the crime.

7. Pose 'alternative q', two choices as the reason behind the crime - one being more socially okay.     Any leaning towards a choice,  will be admission of guilt.

8. Get suspect to admit guilt in front of witnesses.

9. Document their admission and get them to sign a written confession.

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John Duffy Case Study

Aim: Systematically document crimes, crime details, locations chronologically and geographically mapping crimes in order to profile the offender. Canter used his Investigative Psychology in order to identify 'the railway killer'.

This includes: 1) Victim & Offender encounter will reveal offenders social competenece.                                    2) Scientific approach is essential, consider ALL evidence available.                                            3) Offender initially likely to commit crimes in a familiar place.

Findings: 'Marauders' = An offender who offends within work/home location.                                               'Commuters' An offender who travels out of home town to offend.

Canter came up with his Circle Theory from georgaphically mapping this case.

Conclusion: Canter's profile and John Duffy nearly identically similiar. This was the first case to use behavioural characteristics to identify a criminal. Circle Theory, geographical profiling and differentiating personality traits all proved effective.

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Aim: To document a case of false confession.

Sample: Case study of 17 y/o, avergage intellifence, no mental health issues.

Procedure: Case study compiled from several police interviews w/ the suspect & later a psych exam & psychometric tests. First police interview, lasted 14 hours w/ some breaks conducted by 5 police officers alone, leading questions, accusations of lyting/guilt, taunts about sexual impotence. The 2nd interview w/ a duty solictior resulted in retraction of statements, but he confessed later under further pressure. The crime was ****, theft and murder of 2 elderly women.

Findings: He was found to have an abormally high score on GSS, of 10. IQ of 94, and according to EPI was a stable extrovert, he was found to be the coerced-compliant type of confession.

Types: Voluntary, Coerced-Internalisation (made to believe), Coerced-Compliant (want escape)

Conclusion: This case proves it is not only vulnerable people such as disabled, mentally ill etc that are subject to this and that it can happen to anyone under distressing, illegal, pressuring techniques such as those used by the police here.

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Top Down Typology

Theorised that offenders can be categorised in to organised or disorganised, this was beginning of the USA approach to profiling. Data was gathered via in-depth interviews with 36 convicted sexually orientated American murderers, inc. Ted Bundy and Charles Manson.

A crime scene can be used like a fingerprint to ID a murderer, by examing it for characteristic traits and habits etc. 

Examples of organised offenderUse of restraints, brings weapon to the scene                                                                            Crime scene is orderly, reflects planning and control.                                                                  Avg to high intelligence, socially competent, likely employed. 

Examples of disorganised offender: 

Crimes of pasison, spontaneously commit crimes                                                                       No planning - uses weapon of availability.                                                                                 Leaves lots of physical evidence                                                                                             Lower intelligence, socially and sexually incompetent, unemployed etc.

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