Disappearance of Delphine Jubillar: why Cédric Jubillar does not pass the lie detector

The polygraph, or more commonly known as a lie detector, is a technique often used in films and series to allow investigators to close a case. And by dint of seeing this method used on the screens, many people are wondering why the police are not using it in the Jubillar case. Delphine Jubillar disappeared on the night of December 15 to 16, 2020 and, a year and a half later, investigators have still found no trace of the mother. The main suspect who was indicted for spousal murder in June 2021 is Cédric Jubillar, the nurse’s husband of 33 years with whom she was in the process of divorcing. Only until proven otherwise by the competent authorities, Cédric Jubillar – who denies having anything to do with the disappearance of Delphine – is still presumed innocent.

Would passing Cédric Jubillar to the lie detector be a solution to allow the police to know whether, yes or no, he killed Delphine Jubillar, or if he at least knows where she is? A priori, no. Despite what the series and films tell us, the polygraph is not a reliable tool and, in France in any case, therefore has no evidential value in the courts. If it is not used in interrogations, it is because its effectiveness has been questioned on many occasions, in particular because it is possible to cheat the test. The polygraph is based on three measurements: blood pressure, respiration, and the electrical resistance of the skin. These criteria were chosen because according to the different people who have worked on lie detectors, a person who lies exhibits measurable natural reactions such as increased heart rate or excessive sweating – which makes the skin more conductive.

Cédric Jubillar will be interviewed on September 23

Only it happens that people who are too stressed by the simple fact of going to the polygraph obtain results which indicate a lie when they are only the product of his stress. It is also possible that some individuals have physiological reactions different from the average, or that they are indeed lying but for a reason other than that for which they are questioned. As TF1 Info reminds us, the series Le Bureau des Légendes even offers a scene that shows how to outsmart a lie detector by controlling your breathing, which will influence your heart rate. Even if Cédric Jubillar passed the lie detector and the results indicated that he is guilty in the case of the disappearance of Delphine Jubillar, theThe results would not be accepted as evidence in court. This is undoubtedly the main reason why Delphine’s husband does not pass a polygraph and will surely never pass one. Despite everything, the investigation continues with a new interrogation of Cédric Jubillar scheduled for September 23 about broken glasses from his missing wife.