Delayed reception of live blowfly (Calliphora vicina and Chrysomya rufifacies) larval samples: implications for minimum postmortem interval estimates

Forensic entomology evidence collected by police and mortuary staff may be delayed in getting to the entomologist. Live samples may continue developing and alter minimum postmortem interval (PMI_min) estimates. This study investigated development of simulated evidential samples of Calliphora vicina Robineau-Desvoidy and Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) maggots. Maggots of each species were studied in three developmental classes: “small” (late second/early third instar), “mid” (mid third instar) and “large” (late third instar). Seven replicates of 11 maggots in each class were assigned without food to four treatments: (1) 24 h at 20 °C; (2) 24 h at 4 °C; (3) 48 h at 20 °C and (4) 48 h at 4 °C. There was a significant difference in absolute length change across treatments, reflecting size for C. vicina, and interaction between size, time and temperature for Ch. rufifacies. Calliphora vicina maggots showed minimal mortality, and most second instar larvae moulted by the experiment's end. Chrysomya rufifacies showed heavy mortality and minimal moulting from the second to third instar. Only “large” Ch. rufifacies maggots kept at room temperature for 48 h pupariated. Since these results confirm that development can continue in live unfed maggot samples after their collection, it is not advisable to delay their preservation.

Benchmarking forensic rulers and photographic techniques

Measuring various items (evidence) at the scene of an investigation, exposed to the elements, is an instrumental part of systematic forensic science. The key to these measurements often rest on rulers, and a knowledge of their limitations is vital to their appropriate application. The aim of this study was to test forensic ruler accuracy and photographic distortion under conditions that simulate common use to provide a foundational basis for baseline accuracy of their use. A series of ABFO rulers from 2 anonymous manufactures were tested against gold standards for accuracy at various temperatures (-14, 0, 25 and 40 °C). At the same time a series of rulers were photographed at different angulations to test reproducibility and angular distortion. At room temperature a variation of 0.28% in the dimensions of the rulers were found with larger distortions at colder temperatures. Photographs taken with the camera above the rulers suffered the least distortion (approximately 6-10°) and there was no difference over time, nor with ruler background colour. The results from this study show that further investigation is required into preventing angular distortion, and show the need for increased training to those who would be in a situation requiring them to document the scene of a crime.

Bite marks: physical properties of ring adhesion to skin--phase 2

Bite Marks: This study demonstrated that surface wetness was the most influential factor affecting ring adhesion to skin. Also, chemical depilatories and shaving creams were to be avoided when cleaning the skin. The second phase of this research examines the tensile stress needed to rupture the bond between TAK(®) hydroplastic, three new cyanoacrylates, and pigskin with particular consideration for temperature variations. This study also considers solubility issues of different cyanoacrylates in 10% formalin. Finally, the Dorion Type V bitemark excision technique could significantly reduce the risks of tissue distortion when used in conjunction with the following methods and materials. The skin should be devoid of moisture, razor shaved, and cleaned with dishwashing detergent and 98.9% ethanol while avoiding the use of shaving creams and/or chemical depilatories where ring placement is anticipated. The use of unopened cyanoacrylate is encouraged with Permabond(®) as the cyanoacrylate of choice.

Bite marks: physical properties of ring adhesion to skin-phase 1

Unsupported excised skin may shrink by as much as 50% or more. In 1981, a method was developed for ring adhesion to skin with the goal of minimizing tissue distortion upon excision. Five modified versions of the technique bearing the author's name followed (Dorion types I, II, III, IV, and V). The scientific literature reveals little supporting empirical evidence for the preferential use of one adhesive/suturing technique over another. This study compares the use of various bonding materials (Loctite Super Glue gel(®) , Dermabond™, Vetbond™), cleaning agents (ethanol, dishwashing liquid, and shaving cream), and depilatory (Veet(®) ) on the effects of ring adhesion to skin. The conclusions indicate that surface wetness is the most influential factor affecting ring adhesion to skin, followed by the type of bonding material, its "freshness," and by the cleaning agent used to prepare the skin. The use of a depilatory or shaving cream is to be avoided.