6 month 6 daySankei Shimbun morning edition (page 17 Hanshin/Kobe column) "From Hyogo", titled "Surprise at the Reliability of Polygraphs," published an article about the polygraph analysis that Professor Nakayama was in charge of when he was working at the Shizuoka Prefectural Police Headquarters' Forensic Science Research Institute.
In the 27 years he worked at the forensic laboratory, he conducted more than 200 polygraph examinations, of which about XNUMX were murder cases.The veteran police officer of the First Investigative Division, who specializes only in murder cases and other violent crimes, had a particularly strong workmanship and pride among detectives. I worked with confidence.Most of the murder investigation headquarters neither respected nor pandered to each other's opinions. was almost non-existent.
The incident described in this article is an extremely rare case in that sense.At first, he was suspected of having killed his wife and dismembered the corpse with an electric saw and abandoned it in the mountains.The suspect reluctantly admitted to the murder because there was solid physical evidence that the DNA analysis of the belongings was consistent.So, furthermore, a polygraph examination was conducted regarding the additional charges that he may have killed a colleague at his workplace.Immediately after the inspection is over, the detective enters the interrogation room.At this time, the detectives of the First Investigative Division were replaced by a group of 2 people, a total of 1 groups of 3 people, and they took turns investigating the suspect.Judicial precedents show that killing one person is not likely to result in death penalty, but killing two people increases the probability of being sentenced to death by about 6%.For this reason, even the true culprit usually does not admit to murdering two people so easily.
At this time as well, after several hours of stubborn denial from the suspect that "the second person never did it", the investigation headquarters meeting.The polygraph expert clearly showed the measured waveform and confidently reported that there was a response.However, something unexpected happened here.spotWhile only one group claimed that the suspect was Kuro, the remaining two team leaders (assistant inspectors) both concluded that the suspect was Shiro.In short, the two groups' report, which categorically denied the results of the polygraph analysis, confounded the entire 1-member investigative headquarters and raised tensions to the highest point.In other words, a split decision of 2: 2 over whether the true criminal or innocent suspect is reported by four people in total for the investigation and forensics.For several days, the suspect did not confess, there was no evidence, and the lawyer protested that he was illegally pursuing additional charges.At this time, the upper management instructed, "Don't push yourself any further," and the suspect was indicted on only the first murder charge, and the Murder Case Investigation Headquarters was dissolved.
However, after that, when the fiscal year changes and it is time for personnel changes, the chief of the local police station and the chief of the First Investigative Division are renewed.At the time of the total replacement, the new executives, who believed in the results of the polygraph analysis, insisted strongly that "Since they are responding to the polygraph so much, there must be physical evidence somewhere. Find it out." And request another polygraph examination.I rearranged the question somewhat, but of course the result is the same as last time.In addition, the Mobile Forensics Team managed to find the car that the suspect used at the time, which was supposed to have been scrapped at the time of the re-investigation. The board, console box, and trunk room are cut one by one and re-verified to the inside.As a result, I found a mass of blood stains from the deepest part of the passenger seat. The DNA test matches the blood of the victim.The suspect gave up on the third day from the start of the second interrogation and confessed to the second murder.In addition, the defendant admitted to the charges at the trial court, so the death penalty was confirmed.
Why, then, did interrogation and polygraph analysis become so opposed to each other in this case?During the interrogation, the detective only sees changes in the suspect's complexion (facial capillaries).If a criminal has such an abnormal personality that he kills not only his wife but also his co-workers for trivial reasons, his complexion will not change easily no matter what he is asked. Even if you look at it, it's hard to catch it.On the other hand, in polygraph analysis, changes in electrocardiogram, respiratory motion, and skin conductance that occur in response to each question are displayed as visible waveforms in real time.Therefore, even if the suspect has advanced criminality, it is possible to reliably and scientifically detect subtle psychological changes, so the accuracy of appraisal as to whether or not the suspect was involved in the case is dramatically higher than the intuition of a detective. do.In this case, the difference may have appeared as a result.
In any case, the results of the interrogation and the polygraph analysis have never been so diametrically opposed.The results of the investigators' obsession with discovering solid physical evidence using only the suspect's psychological reactions captured by the polygraph as clues.In that sense, it was one of the memorable events.
By the way, there is another interesting story in this case, the "nosebleed episode" that the suspect claimed as a basis for his innocence.investigative psychologyI will tell you in class.
