Volume 17. Number 1
December 2018

Original Articles

A Forensic Examination of Anonymous Browsing Activities 

Szu-Yuan Teng ; Che-Yen Wen

Abstract°GInternet crime has become a serious problem. Cybercriminals use the Darknet to sell some software tools in the black market, such as DDOS attack software, ransomware, Crimeware-as-a-service (CaaS), and other cybercrime tools. Users can use the Tor browser with incognito functions to connect to the Darknet and conduct transactions in the black market. Besides, there are some anonymous browsers with the functions of hiding the webpage activities of users. Although these browsers cannot be used to connect to the Darknet directly, they can let a criminal connect to the Internet anonymously and hide all criminal activities. Therefore, the investigation of digital evidence from the used records of anonymous browsers is full of critical challenges. In this paper, we demonstrate how tools and programs can be used in forensic analysis of anonymous browsers. There are six types of anonymous browsers in our experiments: Epic Privacy Browser, Secure Browser, Comodo Dragon, SRWare Iron, Dooble, and Maxthon. The experimental results show the capability of those tools and programs in the investigation of digital evidence.

A Preliminary Study on the Venous and Menstrual Blood Identification by Methylation-Specific PCR

Kuo-Lan Liu ; Li-Chin Tsai; Yu-Chih Lin ; Chih-Wen Su ; Lih-Jing Yang ; James Chun-I Lee  ; Hsing-Mei Hsieh

Abstract°G This study reported the development of methylation-specific PCR (MSP) to discriminate the venous blood and menstrual blood for the forensic purpose. Initially, a total of 37 candidate markers were evaluated. Six markers of them were obtained by reviewing the references, and the other 31 markers were from the Infinium Illumina Human Methylation 450 BeadChip analysis. DNA sequencing results showed that 11 out of 37 markers contained differentially methylated regions between venous blood and menstrual blood. However, only four markers (CD93, EXD3, ELOVL5 and FLJ42875) comprised the intensive methylated CpG regions which were suitable for MSP analysis. A 4-plex MSP amplification system was established and used on identifica - tion of 9 biofluids samples (3 venous blood, 3 menstrual blood and 3 semen samples). The results showed that the methylation percentages were 6.6°”3.4% (CD93), 5.7°”9.9% (EXD3), 0.0°”0.0% (ELOVL5) and 100.0°”0.0% (FLJ42875) respectively in ve- nous blood, which were hyper-methylated or hypo-methylated. However, the methylation percentages were 38.4°”6.7% (CD93), 62.9°”15.3% (EXD3), 21.9°”5.7% (ELOVL5) and 64.7°”11.8% (FLJ42875) respectively in menstrual blood, which were partially methylated. The preliminary results showed that the methylation patterns of this system were with the potential to discriminate the venous blood and menstrual blood. This 4-plex MSP system offered the alternative method to discriminate venous blood and menstrual blood for forensic purpose.

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Polarized Light Microscopic Examination of Mechanical Damage on Fabric Fibers

Yu-Ting Hsiao  ; Hsien-Hui Meng

Abstract°G Fabric fibers are an important type of trace evidence that can be used to establish connections among individuals, crime scenes, and objects. In addition to the identification of fabric fibers, the examination of fabric damage also plays an important role in forensic investigation as to reconstruct an assaulting incident. Optical microscopy and scanning electron microscopy (SEM) are often used to determine the distinct morphology of fiber ends caused by different forms of mechanical damage. However, the price of SEM is not affordable to the local forensic science departments. Thus, a polarized light microscope (PLM), which is relatively inexpensive and accessible to local police laboratories, was used in this study in order to differentiate the fabric damages caused by cutting with scissors, slicing with scalpel blade, puncturing with screwdriver and discharged bullet, and ripping with hands. The results revealed that the examination procedure used in this study was able to identify the distinct characteristics in fiber ends broken by bullet, scissors, scalpel blade, Philips screwdriver, and ripping. Fabric damage caused by sharp-edged instruments produced neat fiber ends and localized interference color change under PLM. Damage created by puncturing the fabric by non-cutting means, producing irregular holes, which also resulted in rough and elongated broken fiber ends. Interference color change and bright transverse stripes were observed in these uneven fiber ends under PLM due to the change of birefringence property, stress state, and thickness. Whereas uneven fractured fiber ends without interference color change were observed when fabric yarns were pulled apart by ripping. Because characteristic features of damaged fiber ends are affected not only by varied forms of mechanical damage but also the fiber type, yarn structure, and fabric construction and orientation, it is recommended to carry out simulation experiment on the same type of fabric as that found in the forensic case to reconstruct.

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Estimating the Impact Velocity of Airgun Pellet Via Terminal Ballistic Experiments

Yu-Ting Hsiao; Hsien-Hui Meng

Abstract°G Airguns are low-powered weapons that use compressed air to discharge pellets. They are sometimes purposely fired to break glass windows and windscreens in criminal incidents. Forensic experts are frequently required to determine the impact velocity of fired pellet in the cases that the airgun is not available for firing test. The aim of this study is to estimate the impact velocity via the analysis of the crack patterns in the glass and the deformation features of the fired pellet. Terminal ballistic experiments were conducted using airguns and lead pellets to shoot glass sheets at varied velocity. Crack patterns including conical, radial, and concentric cracks were found in glass targets. The results show that the size of conical crack is roughly proportional to the impact velocity. Thus the conical crack pattern can be qualitatively used to estimate the approximate range of the impact velocity. The hollow-structured lead pellet tended to deform after impacting the glass sheet. The mushrooming deformation caused the increase of diameter and the decrease of length for the deformed pellet. Some mushroomed material fragmented from the pel- let and caused the decrease of diameter at the highest impact velocity. Statistical analysis reveals that the length decrease shows strong correlation with the impact velocity (r = 0.93 and r 2 = 0.87) and significant dependence on the impact velocity (p = 3.1°—10 -6 for ANOVA). The simple linear regression equation for the length decrease vs. the impact velocity is suitable for quantitative estimation of the impact velocity and legal status determination for the fired airgun. Because the terminal ballistic effects are affected by the features of both pellet and target, it is recommended that the same type of pellet and glass sheet involved in the shooting incident shall be used while conducting terminal ballistic experiments for the estimation of the impact velocity.

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Personal Identification of Homicide Skeletal Remains in Taiwan Through Combined Contribution from Pathological, Odontological, Anthropological, Entomological, and DNA-STR Analyses

Wei-Len Yan; Kai-Ping Shaw ; Chuan-Chung Tung ; Chiou-Herr Yang

Abstract°G In 2014, parts of skeletonized human remains were exposed in a shallow grave along the hill in Taoyuan, Taiwan. After careful excavation, skeleton of human remains were reconstructed to be one deceased, and the blunt forced injury found in the skull indicated that it is a homicide case. The corpse was found to be in a high degree of decay. The face and fingerprints of the corpse was unable to be recognized. The lack of clothes, accessories and personal belongings also made it difficult to recognize the victim. Forensic pathologist and police tried to identify the remains with multidisciplinary. Forensic pathology provided the injury of the victim and the cause of death. Forensic anthropology provided the ante-mortem biological information of the remains such as gender, height and age. Forensic entomology provided the minimum post-mortem interval (PMI) of the victim. Forensic odontology provided the preliminary personal identification by comparing the teeth of the victim and dental records. After initial personal identification, the identity of victim was confirmed by DNA analysis. The suspect was soon caught by police after the identity of the remains was confirmed. This case report illustrated the important contributions from multidiscipline team including forensic pathology, anthropological, entomological, odontological and DNA analysis to the identification of unknown homicide victim.