The Effect Of Countermeasures On The Detection Effectiveness Of The Item-source Memory Complex Trial Protocol

One of the important issues that needs to be addressed for the Concealed Information Test(CIT)to be widely used in judicial practice is to maximize the scientific accuracy of the test results and make them less susceptible to countermeasures taken by the criminal.The most crucial use of the item-source memory complex trial protocol(i-s CTP),the first globally developed ERP-CIT test that can successfully distinguish between the guilty and the knowledgeable innocent,is to accomplish this.But as of now,it’s unclear whether countermeasures can influence the detection effect when subjects accept i-s CTP.In this study,we attempted to investigate whether countermeasures can interfere with the detection of i-s CTP when taken by the guilty.A countermeasure group,a guilty group,a knowledgeable innocent group,and an unknowledgeable innocent group were each set up in this study,and i-s CTP was performed on each group.In the i-s CTP,the first part of each trial was randomly presented with the probe or one of the four irrelevant stimuli,and the subjects in the countermeasure group were asked to think of their names when the three irrelevant stimuli "earring,watch,bracelet" were presented.The P300 index,which reflects spontaneous neural activity for meaningful information,was measured.The subjects in the countermeasure group were instructed to think of their mother’s name when presented with the two other source words "fetched,sought" and to measure the LPC evoked when extracting the corresponding source memory in the second part of each trial,which involved randomly presenting either the source words of steal(i.e.,stole,pilfered,burglarized)or other source(i.e.,fetched,sought,found).When the relevant source memory was extracted,the evoked LPC index was calculated.The results showed that when the countermeasure group took the countermeasure operation for the irrelevant stimuli,the difference between the P300 amplitude evoked by the probe in the countermeasure group and the guilty and knowledgeable innocent groups was not significant,the P300 amplitude evoked by the irrelevant stimuli in the countermeasure group was significantly larger than that in the guilty and knowledgeable innocent groups,and the difference between the P300 amplitude evoked by the probe and the irrelevant stimuli was not significant in the countermeasure group.The difference between the P300 amplitude evoked by the probe and the irrelevant stimulus in the countermeasure group was not significant.When the countermeasure group performed countermeasure operations on other source words,the difference between the LPC amplitudes of steal source words after the probe evoked by the countermeasure group and the guilty group was not significant,and the LPC amplitudes evoked by other source words after probe in the countermeasure group were significantly larger than those evoked by the guilty group.When performing the i-s CTP,interfering with other source words had less effect on the detection results than interfering with irrelevant stimuli.Although the countermeasures taken by the countermeasure group against other source words influenced the test results,the AUC of LPC distinguishing the guilty countermeasure group from the knowledgeable innocent group still had 0.83,indicating that i-s CTP had some resistance to countermeasures taken by the subjects against other source words.The ability of the i-s CTP to resist subjects’ countermeasure must be continually improved in the future in order to provide better technical assurance for judicial practice.