Forgery detection from printed images: a tool in crime scene analysis

.The preliminary analysis of the genuineness of a photo is become, in the time, the first step of any forensic examination that involves images, in case there is not a certainty of its intrinsic authenticity. Digital cameras have largely replaced film based devices, till some years ago, in some areas (countries) just images made from film negatives where considered fully reliable in Court. There was a widespread prejudicial thought regarding a digital image which, according to some people, it cannot ever been considered a legal proof, since its “inconsistent digital nature”. Great efforts have been made by the forensic science community on this field and now, after all this year, different approaches have been unveiled to discover and declare possible malicious frauds, thus to establish whereas an image is authentic or not or, at least, to assess a certain degree of probability of its “pureness”. Nowadays it’s an easy practice to manipulate digital images by using powerful photo editing tools. In order to alter the original meaning of the image, copy-move forgery is the one of the most common ways of manipulating the contents. With this technique a portion of the image is copied and pasted once or more times elsewhere into the same image to hide something or change the real meaning of it. Whenever a digital image (or a printed image) will be presented as an evidence into a Court, it should be followed the criteria to analyze the document with a forensic approach to determine if it contains traces of manipulation. Image forensics literature offers several examples of detectors for such manipulation and, among them, the most recent and effective ones are those based on Zernike moments and those based on Scale Invariant Feature Transform (SIFT). In particular, the capability of SIFT to discover correspondences among similar visual contents allows the forensic analysis to detect even very accurate and realistic copy-move forgeries. In some situation, however, instead of a digital document only its analog version may be available. It is interesting to ask whether it is possible to identify tampering from a printed picture rather than its digital counterpart. Scanned documents or recaptured printed documents by a digital camera are widely used in a number of different scenarios, from medical imaging, law enforcement to banking and daily consumer use. So, in this paper, the problem of identifying copy-move forgery from a printed picture is investigated. The copy-move manipulation is detected by proving the presence of copy-move patches in the scanned image by using the tool, named CADET (Cloned Area DETector), based on our previous methodology which has been adapted in a version tailored for printed image case (e.g. choice of the minimum number of matched keypoints, size of the input image, etc.) In this paper a real case of murder is presented, where an image of a crime scene, submitted as a printed documentary evidence, had been modified by the defense advisors to reject the theory of accusation given by the Prosecutor. The goal of this paper is to experimentally investigate the requirement set under which reliable copy-move forgery detection is possible on printed images, in that way the forgery test is the very first step of an appropriate operational check list manual

A cold case: A forensic review nine years after the crime

The goal of this presentation is to provide information about potential capabilities and limits of forensic entomology analyses on an old case in order to determine time of death. This presentation will impact the forensic science community by underlining how our current understanding of the forensic sciences can help solve old cases and how important it is to have a DNA database of forensically important insects. Three days after the disappearance of a teenage girl from a small city in the South of Italy the corpse of a girl was found in a wood not far from that city. Immediately it was clear that the girl was murdered and moreover the crime scene appeared to be an execution. She was still clothed, but her hands and feet were tied with wire, her head was covered with a supermarket plastic bag and her eyes were hidden by a plastic tape. The murdered girl was recognized as the girl who disappeared. The autopsy noted that she was not sexually abused, but there were many contradictory observations about the cause of death. The head of the girl sustained a bloody wound and the plastic bag over her head was not sealed properly, so there was a large mass of fly larvae on the head wound and in the eyes. The entomological evidence was poorly sampled and not used at the time, instead the level of humidity of the girl’s clothes was used to determine a contradictory time of death. Many medicolegal professionals were consulted and each one wrote a different conclusion. Two years later, the investigation led to a male suspect who was found with a note written by the girl. However, after two years of imprisonment he was exonerated. The case was reopened six years later and the prosecutors who were handling the case decided to use another team of investigators and they also decided that a forensic entomology analysis might be useful to determine the time of death. All entomological samples collected during the autopsy were destroyed some years before, so the work was performed with the collaboration of old and new investigators and based only on reports, pictures, crime scene and autopsy video, the girl’s clothes and meteorological data from the area nearest to the crime scene. Desiccated insect material was collected after eight years from the girl’s clothes and because of the state of this evidence a morphological examination was not possible. Instead using mtDNA analyzes (COI) the insect material was determined to be Lucilia sericata (determined by a taxonomist). To identify the instar of the desiccated larvae a lab experiment was designed in order to identify the original length of maggots before the dehydration process. This experiment revealed that the larvae from the body of the girl were 2nd instars of Lucilia sericata. This information together with the environmental parameters and the ecological data helped to determine when the eggs were deposited and therefore the most probable time of death. The investigation is still in progress

A cold case: Can forensic entomology be useful 9 years after the crime?

On June 2001, during the afternoon an 18 years old girl disappeared from a small city in the South of Italy. Three days later the corpse of a girl was found in a wood not far from the city. She was dressed, her hands and feet were tied with wire and her head was covered with a plastic bag. The murder appeared to be an execution. The autopsy confirmed that it was the same girl that disappeared. It was determined that she was not sexually abused, but there were many contradictory observations about the cause of death. The head of the girl sustained a bloody wound and the plastic bag over her head was not sealed properly, so there was a large mass of fly larvae on the head wound and in the eyes. The entomological evidence was poorly sampled and not used, instead the level of humidity of the girl’s clothes was used to determine a contradictory time of death. On February 2003, the investigation determined a male suspect who was found with a note written by the girl. After two years of imprisonment he was exonerated. At the end of 2007 the case was reopened and the Prosecutors who were handling the case decided to use forensic entomology to determine the time of death. Entomological samples collected during the autopsy were destroyed some years before, so we worked only on reports, pictures, crime scene and autopsy video and the girl clothes. Furthermore, meteorological data from the area nearest to the crime scene was also available. Desiccated insect material (eggs and larvae) was collected from the girl’s clothes and because of the state of this evidence a morphological examination was not possible. Instead using mtDNA analyses (COI) the insect material was determined to be Lucilia sericata (determined by a taxonomist). To identify the instar of the desiccated larvae we designed an experiment whereby different stages of Lucilia sericata larvae were desiccated and then the length was calculated before and after the dehydration process. This experiment revealed that the larvae from the body of the girl were 2nd instars of Lucilia sericata. This information together with the environmental parameters and the ecological data we determined when that eggs were deposited and therefore the most probable time of death. Based on this information a new investigation is being conducted

Gli insetti a servizio degli inquirenti

Per molti anni gli insetti che popolavano la superficie e gli orifizi dei cadaveri sono stati considerati solo una presenza poco gradevole del lavoro dei medici legali e delle Forze dell’Ordine coinvolte nelle indagini inerenti a crimini violenti. Ma come gli intriganti romanzi di Deawer e della Cornwell ci hanno insegnato, gli insetti costituiscono dei silenziosi custodi di preziosi informazioni sull’accadimento di fatti a volte inspiegabili. Tuttavia mentre le varie branche delle scienze criminalistiche (la biologia, la balistica, la chimica, ecc.) hanno avuto nel tempo una crescita esponenziale, affinando tecniche e metodologie, lo studio degli insetti associati alla scena criminis è stato, nel nostro Paese per molto tempo sottovalutato o addirittura ignorato. L’Entomologia Forense è un ramo della zoologia dedicata allo studio degli insetti e di altri artropodi, dal cui esame è possibile ricavare elementi decisivi per la persecuzione di un reato. Negli ultimi anni tale disciplina ha visto crescere l’interesse da parte degli scienziati forensi, dei Medici Legali e delle Forze dell’Ordine, soprattutto in Europa e negli USA, dove esistono figure professionali specialistiche che affiancano la magistratura inquirente nella risoluzione di casi di morti sospette ed altri reati accomunati dalla presenza di insetti. Purtroppo in Italia solo da pochi anni si è sviluppato l’interesse verso la materia e ancora oggi gli entomologi forensi non lavorano sistematicamente accanto agli organi di Giustizia. Lo scopo del presente lavoro è una disamina delle potenzialità dell’Entomologia Forense e delle relative applicazioni come strumento spesso determinante per la risoluzione di intriganti e complessi casi giudiziari