Forensic Psychology: Detecting Deception

Definition: A successful or unsuccessful attempt, without forewarning, to create in another a belief which the communicator considers to be untrue (Vrij, 2000, p.6).
Key components of deception include intent, lack of forewarning, and that success is not relevant.
Main types of deception consist of falsifications, distortions or exaggerations, and omissions.

Catching a liar relies on three main approaches: physiological or formal techniques, nonverbal or body language cues, and verbal cues.
The polygraph was invented by William Marston (1917) and refined by John Larson (1932) to measure heart rate, blood pressure, breathing (rate and depth), and Galvanic Skin Response.
Control Question Technique (CQT) compares reactions across neutral questions, crime-relevant questions, and embarrassing control questions, but is prone to false positives (Vrij, 2000).
Guilty Knowledge Test (GKT) evaluates reactions to crime-specific details paired with alternative options; it applies to fewer than $15\%$ of FBI cases (Podlesny, 1993) and is prone to false negatives (Vrij, 2000).
Countermeasures using physical or mental techniques are highly effective (Honts et al., 1994), enabling $50\%$ of subjects to beat the CQT after $30\,\text{mins}$ of training, with only $12\%$ of physical countermeasure users detected.

Thermal Imaging measures instantaneous anxiety with accuracy reported at $83\%$ by Pavlidis et al. (2002) and $67\%$ by Warmelink et al. (2011), but is prone to false positives.
ERP Analysis (Brain-fingerprinting) measures changes in the $P300$ waveform using an orienting technique with GKT, achieving accuracy rates of $82\%$ to $88\%$ (Mertens & Allen, 2008).
fMRI Scanning tracks central nervous system blood flow, highlighting prefrontal cortex activity (executive control) and anterior cingulate cortex (ACC) activity (risk and reward assessment), with accuracy rates of $78\%$ to $93\%$ .
fMRI limitations include inconsistent brain activity patterns between spontaneous and rehearsed lies (Ganis et al., 2003), high costs, and unresolved legal and ethical challenges (Langleben & Moriarty, 2013; Tennison & Moreno, 2012; US v Semrau, 2010).