Differentiation of black gel inks using optical and chemical techniques

Gel ink pens have become a common writing instrument in the United States. Questioned document examiners often attempt to optically differentiate gel inks from each other and from other non-ballpoint ink writings (e.g., those from roller-ball pens). Since early formulations were primarily pigment-based, they do not elute when analyzed by thin-layer chromatography. However, recent gel ink formulations (i.e., within the past five years) include dye-based inks that can be easily separated. This study differentiates black gel inks using optical and chemical techniques. The techniques include: microscopy, visible and near infrared reflectance, near infrared luminescence, thin-layer chromatography (TLC), spot tests, and gas chromatography/mass spectrometry (GC/MS). As a result of this study a flow chart has been developed allowing for a systematic determination of a questioned ink. In addition, an analysis of volatile compounds found in gel inks revealed that there are some unique ingredients that may be found in gel inks that are not typically found in other non-ballpoint inks.     

Adolescent self-poisoning: a cohort study of subsequent suicide and premature deaths

Previous self-harm has been identified as a risk factor for subsequent suicide by adolescents. The objective of the study was to identify further risk factors for subsequent premature death and suicide in a population of adolescents presenting with self-poisoning. A longitudinal cohort design using data-linkage of consecutive adolescent patients presenting to the Hunter Area Toxicology Service, a regional toxicology service for Newcastle, Australia, with the National Death Index of the Australian Institute of Health and Welfare was used. A total of 441 adolescents aged 10 to 19 years presented with self-poisoning over 5 years from January 1991 to December 1995, with follow-up to March 2001. There were 14 deaths total, eight of which were likely suicides. There was a 22-fold increase in suicide rate for males and a 14-fold increase for females compared with age-normalized population rates. Adjusted hazard ratios (95% CI) forpremature death were male gender 3.77 (1.11-12.78), nonaffective psychotic disorders 16.3 (3.83-69.34) and the mental illnesses of childhood 6.12 (1.68-22.23). There was a similar pattern for suicide: Male gender, nonaffective psychotic disorders, and the mental illnesses of childhood confer greater risk for subsequent suicide or premature death in this population.     

Reliability of bloodhounds in criminal investigations

Anecdotal evidence and legend have suggested that bloodhounds are capable of trailing and alerting to a human by his or her individual scent. This same evidence may be presented to a court of law in order to accuse a particular suspect or suspects of a crime. There is little to no scientific evidence confirming the bloodhound's ability to trail and discriminate the scent of different individual humans. Eight bloodhounds (3 novice and 5 veteran), trained in human scent discrimination were used to determine the reliability of evidence, garnered through the use of bloodhounds, in a court of law. These dogs were placed on trails in an environment that simulated real-life scenarios. Results indicate that a veteran bloodhound can trail and correctly identify a person under various conditions. These data suggest that the potential error rate of a veteran bloodhound-handler team is low and can be a useful tool for law enforcement personnel.     

The forensic analysis of thermal transfer printing

Thermal transfer printing refers to printing processes that utilize heat to produce an image by either physical or chemical means or by a combination of both. As the technology has improved and the supplies have become less expensive, the use of thermal printing in the personal and business markets has increased significantly. Specifically, dye diffusion thermal transfer and thermal mass transfer have become predominant in the production of counterfeit credit cards, drivers' licenses, and other types of documents produced on plastic media. Chemical analysis by means of thin layer chromatography (TLC) has proven to be useful in characterizing various types of inks (e.g., writing and inkjet inks). In this study, the authors examined 81 different samples that included a total of 54 printer samples (43 photographic prints on paper and eleven plastic card samples) and 27 printer ribbons. A new TLC method was developed and tested utilizing a solvent system (80% n-hexane, 3% methyl ethyl ketone, and 17% ethyl acetate) that is capable of producing excellent resolution.