中科館大講堂 No matter how cunning the criminals are， they will be brought into justice. The development of science and technology provides a strong support for the detection of criminal cases. Do you want to know that how can this sword make criminals nowhere to hide？ How can modern science and technologies be applied in the investigation work？ On October 29， 2016， we invited Hou Anshan to our lecture who is the director of the Department of Popularization of Science and Technology of Chinese Academy of Forensic Science， and he will explain the science in solving cases.

Q Is psychological testing （lie detector） useful？

A Lie detector is helpful. Because people's psycho-

logical changes can not be subject to their own subjective control， and what they do will leave correspond traces in the minds. Especially for major criminal cases， he can well remember what he did in the case. When a question touches a case he did， his brain will produce a series of thinking reaction， and this kind of thinking response caused by physiological changes will be captured by the instrument. Psychological testing is effective in many cases， although it can not be used as direct evidence， it is useful for us to judge whether the suspect does the case or not.

Q How to use Forensic Entomology to solve criminal cases？

A Most of the entomology is used to determine the dead time of dead bodies. As corpses are exposed and corrupt in the wild， they attract flies and other insects to reproduce on corpses. Investigators in the field will extract some maggots， pupae， pupa shell， etc. so as to determine their formation time through the study and then infer the approximate time of death of the victim. Entomology can also be used in other areas， for example， investigators can indirectly determine whether the victim is taking volatile poison or not according to the survival or death of the insects at the nose and mouth parts of the corpses.