Crime psych-3- Collection of evidence

  • Created by: livvvx
  • Created on: 01-04-19 17:10

Collection of evidence (Cognitive)

Collection and use of evidence from witnesses and suspects:


  • Traditionally a line of around 6 individuals, including the suspect and a number of 'foils'
  • The witness looks through a one-way screen and has to identify the perprtrator from the line-up.


  • Producing an accurate image of someone to fit a witness's description
  • Originally police artists, in the 70's these moved on to photo-fits which involves selecting features (eyes, mouth, nose) from a larger bank of photographic images.
  • FBI still uses artists


  • 1-Witnesses feel under pressure to choose someone- working from the assumption that the suspect is somewhere in the line.
  • 2- Police officers unconsciously passing on clues to the witness i.e. leading questions, bias

Suggested improvement?

  • 1- Tell witness that the perpetrator may or may not be in the line, Show potential suspects one at a time (without saying how many there are) and witnesses have to make a decision on each individual.
  • 2- A suggestion is that police adopt a double-blind procedure where the officer running the line-up is not aware which is the suspect and which are the foils to avoid passing on any clues.

Loftus and Palmer (1974) recap-


  • Procedure- Ps shown video clips of car accidents and asked to estimate speed. Given 1 of 5 verbs in leading question- Smashed, collided, hit, bumped or contacted.
  • Results- 10mph diff between most and least severe verb (Smashed vs contacted)
  • Conclusions- Either memory distortion or response bias


  • Procedure- Ps shown 1 clip of car accident. 1/3 asked leading question with hit, 1/3 with smashed or 1/3 not asked leading question (control). 1 week later asked 'Did you see any broken glass?'
  • Results- Ps twice as likely to remember seeing broken glass in smashed group compared to hit and control.
  • Conculsions- Memory distortion by reconstructive memory.

How can this research be applied to police and their interviewing techniques?

No leading questions should be asked. Witnesses may reconstruct their memory of an event to incorporate info they hear after the event i.e. from other witnesses or from media reports- interviews should take place before this can happen.

Diffs between interviews and interrogations:


  • Non-accusatory
  • Dialogue- question and answer format
  • Aims to elicit investigative and behavioural info 
  • Aims to asses the subject's truthfulness
  • Aims to profile the subject for possible interrogation
  • Note taking following each response


  • Accusatory
  • Monologue- discourage suspect from talking until ready to tell the truth
  • Aims to elicit the truth.
  • Aims to obtain a court-admissable confession if it is believed that the suspect is guilty.
  • No note taking until after the suspect has told the truth.

Reid 9 steps of interrogation

1) Positive confrontation-

  • Tell the suspect that all the evidence confirms that there is no doubt that s/he is guilty of the crime.
  • Interrogator leaves room, returns with folder of evidence, stands directly in front of suspect and in a confident manner/tone of voice, confront the suspect.

2) Theme development-

  • Interrogator attempts to shift blame away from suspect to…


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