Abstract: Finding the truth is a key element in solving criminal cases, so forensic investigators have been searching for appropriate methods to detect lies. Starting from the findings in the field of Psychology which show that, when lying, people have certain patterns in presenting their version of events, forensic experts have tried to create automatic devices which can detect these patterns. Such a device uses the methods developed by the science of Natural Language Processing. The methods consist mainly in using some algorithms in order to find and analyse the content of a text. Although the use of Natural Language Processing in detecting lies is only at the beginning, experiments carried out so far have been showing an accuracy of over 80%, which is a strong impetus for further research in this area. 

Key-words: Forensic Science; Natural Language Processing; deceptive behaviour; truth.