Mann - Police Officers' Ability to Detect Lies

The aim of the study was to investigate police officers' ability to distinguish truth and lies during suspect interviews.

The participants were 99 police officers from Kent, UK. 75 Males and 24 females. 

The method was a field experiment using questionnaire and correlation. 

Participants first completed a questionnaire about their experience in detecting deception.

They secondly watched video clips of 14 suspects in real-life police interviews.

The participants had to judge whether the suspect was telling the truth or lying.

Once they decided if they were telling the truth or lying, they then had to complete a scale of how confident they were about their decision.

They were then asked to list the cues they had used to indicate whether the suspect was telling the truth or lying.

Results

Participants were 66% accurate in detecting lies, and 64% accurate in detecting truth.

There was a weak positive correlation between both experience in interviewing and accuracy in detecting lies, and experience in interviewing and accuracy in detecting truth.

The cues used and listed by participants to detect lies were: gaze, movements, vagueness, self-contradictions and fidgeting.