The use of ethyl cellulose film lifts to collect particle traces from exposed adhesive on the edges of duct tape.

Environmentally acquired particles (EAP), trapped along the edges of duct tape in the exposed adhesive, are a possible source of information regarding prior exposures of the tape and a possible means to associate duct tape rolls to segments of duct tape that are collected as traces during the investigation of criminal activity. The recovery and separation of EAP is complicated by (1) the need to separate the particles from the adhesive, and (2) the presence of adhesive filler and pigment particles that are part of adhesive formulations. Approaches such as cutting the tape edge, followed by solvent extraction, or swabbing of the duct tape edges using solvents, result in thousands of adhesive filler/pigment particles, overwhelming much smaller numbers of EAP.

Identification of factors affecting SEM/EDS analysis for discrimination and classification among common items of evidence using particle combination profiles.

This article presents key factors affecting the analysis of particle profiles as used for discrimination and classification among items commonly collected at crime scenes. Identification of these factors is a necessary step to enable systematic improvement, optimization, and transition to practice. Prior research, employing reasonable initial choices of analytical and statistical parameters, has (1) demonstrated the presence of highly discriminating sets of very small particles (VSP) on the surfaces of items commonly collected at crime scenes, (2) developed statistically rigorous measurements of correspondence between VSP profiles, and (3) produced objective measures for the resulting probative value.

Utility of Non-Identifiable Fingermarks.

Fingermarks that have insufficient characteristics for identification often have discernible characteristics that can form the basis for lesser - yet still useful - degrees of correspondence and probability of occurrence within a population. Currently, those fingermarks that experts judge to be insufficient for identification are not used as associative evidence. However, recent research has shown large numbers of cases where non-identifiable fingermarks (NIFMs) occur that have high potential associative value.

Occurrence and associative value of non-identifiable fingermarks.

Fingermarks that have insufficient characteristics for identification often have discernible characteristics that could form the basis for lesser degrees of correspondence or probability of occurrence within a population. Currently, those latent prints that experts judge to be insufficient for identification are not used as associative evidence. How often do such prints occur and what is their potential value for association? The answers are important.

Differential analysis of very small particles (VSP) from the contact surfaces and recessed areas of footwear.

Prior work has shown that the contact surfaces of footwear rapidly lose very small particles (VSP) when walking on dry soil. Other research, with more general sampling from shoe soles, has shown that particles can persist much longer. Given rapid losses from contact surfaces, we hypothesize that non-contact, recessed areas of footwear retain particles from prior exposures.

Rates of loss and replacement of very small particles (VSP) on the contact surfaces of footwear during successive exposures.

It has previously been shown that a walk of 250 m (approximately 175 steps/shoe) in a new environment is sufficient to remove and replace particles present on the contact surfaces of footwear. However, it is unknown how quickly this replacement occurs. This paper describes experiments measuring how quickly (in terms of steps) this loss and replacement of VSP occurs.

Discrimination and classification among common items of evidence using particle combination profiles.

This project used established analytical tools and statistical methods to determine the evidential value of very small particle (VSP) profiles found on handguns, cell phones, drug packaging, and ski masks. Sampling protocols were designed, tested and used to sample VSP from evidence items from a single county-level crime laboratory: 30 handguns, 31 cell phones, 36 drug packaging specimens and 32 ski masks. Specimens were prepared for analysis employing established protocols for semi-automated scanning electron microscopy with elemental characterization by energy dispersive x-ray analysis (SEM/EDS).

Loss and replacement of small particles on the contact surfaces of footwear during successive exposures.

On the contact surfaces of footwear loosely, moderately and strongly held particle fractions were separated and analyzed in an effort to detect different particle signals. Three environmental exposure sites were chosen to have different, characteristic particle types (soil minerals). Shoes of two types (work boots and tennis shoes) were tested, accumulating particles by walking 250m in each environment.

Utilization of environmentally acquired very small particles as a means of association.

Very small particles (VSP) are ubiquitous in our environment and are virtually ignored by forensic science. These particles range in size from an order of magnitude smaller than conventional trace evidence, down to the molecular level. Combinations of VSP provide an extraordinary, largely untapped resource for forensic associations and source attribution.

Illustration and analysis of a coordinated approach to an effective forensic trace evidence capability.

An effective trace evidence capability is defined as one that exploits all useful particle types, chooses appropriate technologies to do so, and directly integrates the findings with case-specific problems. Limitations of current approaches inhibit the attainment of an effective capability and it has been strongly argued that a new approach to trace evidence analysis is essential. A hypothetical case example is presented to illustrate and analyze how forensic particle analysis can be used as a powerful practical tool in forensic investigations.

Exploitation of very small particles to enhance the probative value of carpet fibers.

Environmentally acquired very small particles (VSP), present on the surfaces of carpet fibers, have shown potential for the association of fibers with their carpet source. To unlock this potential, research is required addressing a number of areas, including the application of methods under realistic casework conditions and the utilization of computational methods for the refinement and testing of the approach. In this work field collections of carpet fibers were conducted by crime scene practitioners under realistic casework conditions.

Critical review of forensic trace evidence analysis and the need for a new approach.

The historical development, contributions and limitations of the two traditional approaches to trace evidence analysis are reviewed. The first approach was as generalist practitioner, looking broadly at an assemblage of many different particle types. The second was that of specialist practitioner, with attention focused on one specific particle type.

A selection of some of Dr. McCrone's high and low profile cases in the forensic analysis of art.

Throughout Dr. McCrone's active professional career of over 60 years, he worked on many cases involving the forensic analysis of art. This is an overview of a small portion of these cases.