A study on the false positive rate of Stegdetect

In this paper we analyse Stegdetect, one of the well-known image steganalysis tools, to study its false positive rate. In doing so, we process more than 40,000 images randomly downloaded from the Internet using Google images, together with 25,000 images from the ASIRRA (Animal Species Image Recognition for Restricting Access) public corpus. The aim of this study is to help digital forensic analysts, aiming to study a large number of image files during an investigation, to better understand the capabilities and the limitations of steganalysis tools like Stegdetect. The results obtained show that the rate of false positives generated by Stegdetect depends highly on the chosen sensitivity value, and it is generally quite high. This should support the forensic expert to have better interpretation in their results, and taking the false positive rates into consideration. Additionally, we have provided a detailed statistical analysis for the obtained results to study the difference in detection between selected groups, close groups and different groups of images. This method can be applied to any steganalysis tool, which gives the analyst a better understanding of the detection results, especially when he has no prior information about the false positive rate of the tool.     

How nonrecidivism affects predictive accuracy: evidence from a cross-validation of the Ontario Domestic Assault Risk Assessment (ODARA)

Prediction effect sizes such as ROC area are important for demonstrating a risk assessment's generalizability and utility. How a study defines recidivism might affect predictive accuracy. Nonrecidivism is problematic when predicting specialized violence (e.g., domestic violence). The present study cross-validates the ability of the Ontario Domestic Assault Risk Assessment (ODARA) to distinguish subsequent recidivists and nonrecidivists among 391 new cases with less extensive criminal records than previous cross-validation samples, base rate=27%, ROC area=.67. Excluding ambiguous nonrecidivists increases the base rate to 33%, ROC area=.74. Random samples of 50 recidivists and 50 unambiguous nonrecidivists yield ROC areas from .71 to .80. Published norms significantly underestimate official recidivism. Ambiguous nonrecidivism is prevalent and leads to underestimating base rates and predictive accuracy.     

How fear of crime affects punitive attitudes

This article investigates different types of fear of crime as predictors for punitive attitudes. Using data from a Germany-wide representative survey (n = 1272) it examines the reliability and validity of survey instruments through confirmatory factor analysis (CFA) and uses structural equation modeling (SEM) to explain variations in the level of respondents’ punitive attitudes. The results show that different emotional and cognitive responses to crime have a distinctive effect on the formation of punitive attitudes. These effects vary significantly depending on socio-demographic factors and assumed purposes of punishment. A crucial observation of the study is that men’s fear of crime works in a different way in the formation of punitive attitudes than women’s fear of crime. The perceived locus of control for the crime threat is a possible explanation for this difference.     

How to reduce turnover by creating a positive work climate

Despite company attempts to reduce employee turnover by offering attractive salaries and benefits, Kushell notes that attrition continues at an alarming rate. He states that more than one of every three employees will change jobs over the next five years, a transition that will take its toll on company morale and productivity. The underlying factor, according to the author, is the quality of the working environment. A 1969 University of Michigan survey of 1,533 workers, at every occupation level, reported that all respondents ranked interesting work and authority to get the job done far ahead of good pay and job security. Sources of employee frustration include a stifling bureaucracy, excessive job expectations, and unsuitable jobs. The author suggests that top managers ask themselves whether they are missing out on or losing talented employees. If this is the case, there are several guidelines management should follow: improve communication between employees and top management; define expectations of the employee; and promote candor in the job interview. Kushell concludes that top executives can have an impact on turnover by paying attention to what employees really want rather than what management thinks they want.     

Evaluation of DNA match probability in criminal case

The new emphasis on quantification of evidence has led to perplexing courtroom decisions and it has been difficult for forensic scientists to pursue logical arguments. Especially, for evaluating DNA evidence, though both the genetic relationship for two compared persons and the examined locus system should be considered, the understanding for this has not yet drawn much attention. In this paper, we suggest to calculate the match probability by using coancestry coefficient when the family relationship is considered, and thus the performances of the identification values depending on the calculation of match probability are compared under various situations.     

论DNA证据的鉴真

DNA证据不具有独特的自然特征与标记,其从物证形态被提取到以鉴定意见形态应用于法庭要经历多环节的流转过程,这使得DNA证据易于被替换且性状也容易发生变化。从实践情况来看,DNA证据被赋予较强证明力,而准确运用DNA证据认定案件事实的前提在于DNA证据的真实性,因此,有必要对其进行鉴真。通过鉴真,可保障DNA证据在诉讼中的合法准入、确保事实认定的准确性以及防止证据替换或毁损。DNA证据鉴真的重点应放在提取过程的可回溯性、证据保管链的完整性和鉴定过程的可靠性三个方面。     

司法精神病鉴定证据价值论

司法精神病鉴定作为科学的认识活动,由于其本身的固有属性及诸多因素之影响,其鉴定结论在很大程度上具有不确定性.因此,要求法官在采信鉴定结论之前,必须结合司法精神病鉴定的特点、司法精神病鉴定结论的证据属性,分析、判断其证据价值.并通过对相关制度的完善,充分发挥庭审质证之功能,帮助法官提升对司法精神病鏊定结论形成内心确信的准确性.     

How child maltreatment affects dimensions of juvenile delinquency in a cohort of low-income urban youths

This study examines how the presence and types of maltreatment affect dimensions of delinquency and whether the relationship is maintained in the presence of sociodemographic factors. A prospective comparison-group design was employed, featuring controls on social class, race, gender, age, and urban residence. A cohort of 632 males from low-income families, living in one of Pennsylvania's largest cities, was tracked through the state's child welfare and juvenile justice systems. Results indicate that the presence of maltreatment significantly affected the initiation and continuation of delinquency. Neglect was found to be a highly criminogenic factor. Race was not associated with maltreatment nor with delinquency.     

DNA profiling of trace evidence--mitigating evidence in a dog biting case

A young girl was the victim of a severe dog attack. An animal, suspected of having caused the attack, was later impounded for investigation. Microclots of blood, recovered from the dog's fur, were analyzed by STR DNA. Results showed that this blood was not related to the biting. Other forensic evidence--hairs, fibers, and odontology--failed to connect a particular animal to the attack. The implications of these findings for the dog and its owners are discussed as well as other forensic methods for resolving such cases.     

Training of legal professionals in DNA evidence

The South African Criminal Legal System is based on Roman Dutch law. Court proceedings are led by a single presiding officer of the court. Prosecutors and defence advocates present the court with evidence in an adversarial manner. This system has inherent advantages and disadvantages and therefore the training of legal professionals in handling DNA evidence in court is important. The prosecutors resort under the National Prosecuting Authority and the defence advocates act independently or e.g. under the auspices of Legal Aid South Africa.Education curricula of legal professional do not include forensic science evidence. Principles such as evidential value in the forensic context are not addressed. Training of legal professionals with our Essential DNA Evidence™ Course has been a multiplier of forensic science knowledge in the legal profession in South Africa. We present prosecution and defence perspectives in an unbiased manner, compensating for the possible subjective interpretations of evidence that may be presented in court. Forensic evidence is subsequently carefully evaluated prior to being court presentation thus improving court efficiency, and allowing for a more focussed approach to the presentation of evidence. Approaches to the customisation of course content that adds value has been identified via evaluation of training programmes.Experience has shown that legal professionals have the ability to incorporate relatively complex scientific concepts into their legal arguments if provided with the appropriate training opportunity. Appropriate training in DNA evidence has made the court process more effective, both in terms of time and costs, and ultimately serves justice.     

Value of DNA evidence in detecting crime

DNA material is now collected routinely from crime scenes for a wide range of offences and the timely processing of the DNA is seen as key to its success in investigating and detecting crime. An analysis of DNA material recovered from the volume crime offences of residential burglary, commercial burglary, and theft of motor vehicle in Northamptonshire, U.K., in 2004 has enabled the DNA to be categorized into seven sources. Further analysis using a logistical regression has revealed a number of predictors, other than timeliness, that greatly influence whether the DNA material recovered from a crime scene enables the crime to be detected. The results indicate that a number of these predictors are of statistical significance and may be just as relevant in determining whether DNA successfully detects the crime as the timeliness of the processing of the DNA material. The most significant predictor was found to be investigating officer accreditation with location, quantity, and type of DNA material at the crime scene also being relevant. Accreditation of the Crime Scene Examiner recovering the DNA material was found not to be significant. Consideration is given to where further emphasis is needed by the U.K. police service to maximize the opportunities to detect volume crime with DNA.