Inferior detection of information from collaborative versus individual crimes based on a P300 Concealed Information Test

Abstract

The present study used a P300-based Concealed Information Test (CIT) to detect individual and collaborative crimes and to explore whether or not the P300 index is effective in identifying collaborative crime members. Participants were divided into two groups to either steal a ring alone (individual group) or collaboratively with another companion participant (collaborative group) before taking the Complex Trial Protocol test that is regarded as an accurate version of the P300-based CIT. The ERP results revealed that both groups showed significantly larger P300s to probe (the ring) than to all irrelevant stimuli (other jewelery), but the P300 amplitude difference of probe stimulus versus irrelevant stimuli in the collaborative group was significantly less than that in the individual group. For the individual diagnosis, using P300 index, the detection rate was significantly inferior for collaborative crime than individual crime, probably related to weakness of collaborative encoding. The ROC curve comparisons showed the individual guilty was effectively discriminated from the simulated-innocent (AUC = .84) and from the collaborative guilty (AUC = .83), but the collaborative guilty was not discriminable from the simulated-innocent (AUC = .66). These findings suggest that collaborative encoding of crime-related information impacts the efficiency of the P300 index, and that the P300-based CIT is not applicable when used to identify collaborative crime perpetrators.

A novel and effective item‐source complex trial protocol: Discrimination of guilty from both knowledgeable and unknowledgeable innocent subjects

“…In addition, the cutoff points are also affected by the base-rate of guilt which may differ from case to case, and the arbitrary cutoffs cannot offer any help to future judicial practices (Lieblich et al, 1978). Therefore, this study did not report the individual diagnostic results as the previous studies did (Deng et al, 2021;Lu et al, 2017;Sai et al, 2020).…”

“…Seventy-four undergraduate students at Hubei University were recruited. Seven participants (three in the guilty group, three in the knowledgeable innocent group, and one in the unknowledgeable innocent group) were excluded because the superimposed average number of probe EEG segments was less than 30 (see Lu et al, 2017). One participant in the knowledgeable group was excluded because the experimenter found out that she did not remember the item she fetched via the post-experiment questionnaire.…”

“…2.6 | Data analysis 2.6.1 | Amplitude and latency P300 evoked by S1 Some studies showed that P300 amplitude was calculated by peak-to-peak method at Pz to ensure high sensitivity in detecting concealed information (Deng et al, 2016;Deng et al, 2021;Lu et al, 2017;Meijer et al, 2007;Soskins et al, 2001). Therefore, the peak-to-peak method was used to measure the probe and the irrelevant P300 amplitudes at Pz, and a time window of 300-650 ms was selected.…”

“…The results of individual diagnosis were usually reported in previous studies (Deng et al, 2016;Lu et al, 2017;Zheng et al, 2019). An individual diagnosis is made for each participant to determine whether he or she is "guilty", which requires the derivation of a BSIT value.…”

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The concealed information test (CIT) is a psychophysiological deception detection method with high internal validity that infers whether an examinee is a guilty person or not by detecting the memory of crime-related information (Lu et al, 2017). The CIT usually measures heart rate, skin conductance response, P300, etc.Traditionally, both the crime-related probe and the crime-unrelated stimuli are presented in an ERP-based CIT.

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