Highlights The use of forensic taggant technologies has become considerably more widespread The application of taggant materials for forensic purposes are described The different coding methods used in commercial marking materials to infer identity are explored Recent developments in the field are discussed along with future perspectives
AbstractThe use of taggant technology to mark objects for the purpose of identification is becoming a significant part of national crime reduction strategies. Taggants may be able to prevent or monitor criminal offences by associating an object with a specific piece of information. While the material properties of a taggant will largely vary between application purposes, a specific 'coding' element will generally be incorporated to infer marker uniqueness. With the speed, simplicity and accuracy of coding component analysis largely determining the overall efficacy of taggants, continuing advances in portable in-field analysis, nanotechnology and material science should have allowed for the development of new and improved forensic marking agents. However, the limited amount of recent research in this area suggests that this is not the case. This critical review therefore examines the current state of presently available taggants before attempting to offer insight into the future direction of forensic marking technology.
One of the most common tasks in criminal investigation is to determine from which tissue source a biological fluid stain originates. As a result, there are many tests that are frequently used to determine if a stain is blood, semen or saliva by exploiting the properties of certain molecules present within the fluids themselves. These include chemical reagents such as the Kastle-Meyer or Acid Phosphatase tests, as well as other techniques like the use of alternative light sources. However, most of the tests currently available have some major drawbacks. In this study, a handheld near-infrared spectrometer is investigated for the specific identification of deposited bloodstains. First, a calibration was carried out by scanning over 500 positive (blood present) and negative (blood absent) samples to train several predictive models based on machine learning principles. These models were then tested on over 100 new positive and negative samples to evaluate their performance. All models tested were able to correctly classify deposited stains as blood in at least 81% of tested samples, with some models allowing for even higher classification accuracy at over 94%. This suggests that handheld near infrared devices could offer great opportunity for the rapid, low cost and non-destructive screening of body fluids at scenes of crime.
Complementing
the demand for effective crime reduction measures
are the increasing availability of commercial forensic “taggants”,
which may be used to physically mark an object in order to make it
uniquely identifiable. This study explores the use of a novel “peptide
coding” reagents to establish evidence of contact transfer
during criminal activity. The reagent, containing a fluorophore dispersed
within an oil-based medium, also includes a unique synthetic peptide
sequence that acts as a traceable “code” to identify
the origin of the taggant. The reagent is detectable through its fluorescent
properties, which then allows the peptide to be recovered by swabbing
and extracted for electrospray ionization-mass spectrometry (ESI-MS)
analysis via a simple liquid–liquid extraction procedure. The
performance of the reagent in variable conditions that mimic the limits
of a real world use are investigated.
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