Peter R. De Forest

Evaluation of Deoxyribonucleic Acid (DNA) Isolated from Human Bloodstains Exposed to Ultraviolet Light, Heat, Humidity, and Soil Contamination

This study was designed to analyze the effects of common environmental insults on the ability to obtain deoxyribonucleic acid (DNA) restriction fragment-length polymorphisms (RFLP) patterns from laboratory prepared specimens. The environmental conditions studied include the exposure of dried bloodstains to varying amounts of relative humidity (0, 33, 67, and 98%), heat (37 degrees C), and ultraviolet light for periods of up to five days. In addition, the effect of drying over a four-day period in whole blood collected with and without ethylenediaminetetraacetate (EDTA) was examined. The results of the study showed that, under the conditions studied, the integrity of DNA is not altered such that false RFLP patterns are obtained. The only effect observed was that the overall RFLP pattern becomes weaker, but individual RFLP fragments are neither created nor destroyed.

The Morphology and Evidential Significance of Human Hair Roots

A discussion of the morphology of human hair roots is presented. In addition to descriptions of variants of the root appearance for hairs removed from follicles in the three classical growth phases, several other commonly occurring root configurations are described and illustrated with photomicrographs. The possible evidential significance of each in certain case situations is discussed.

Individual characteristics of chemically modified human hairs revealed by scanning electron microscopy.

Hair that is treated with several different chemical reagents including those that are proteolytic, denaturing, or disulfide bond-reducing agents, undergoes structural alterations both internally and externally as revealed by scanning electron microscopic analysis. Some of these agents produce varying degrees of morphologic alterations in hairs obtained from different individuals. It would seem that this technique can be useful in the discrimination of human hairs from different individuals, since the chemically induced topological changes on the hair shaft apparently exhibit a high degree of intraindividual consistency.

A Novel Approach to the Examination of Soil Evidence: Mineral Identification Using Infrared Microprobe Analysis

Abstract:  Identification of minerals using the infrared microprobe with a diamond internal reflection objective is a rapid and reliable method for forensic soil examinations. Ninety‐six mineral varieties were analyzed, and 77 were differentiated by their attenuated total reflection (ATR) spectra. Mineral grains may be mounted in oil for conventional polarized light microscope characterization and their ATR spectrum obtained with little or no interference by the liquid. This infrared microprobe method can be used to identify silicates, phosphates, nitrates, carbonates, and other covalent minerals; however, ionic minerals, metal oxide and sulfide minerals, and minerals with refractive indexes greater than diamond do not produce identifiable spectra, but the lack of a spectrum or one with high absorbance values does provide useful information. This research demonstrates the overall utility that infrared microprobe analysis brings mineral identification in soil evidence.

A comparison study of hair examination methodologies

A study was conducted to investigate the accuracy between two methods of hair analysis: PCR-STR DNA analysis and microscopic comparison analysis. Standard sets of pubic hairs were collected from volunteers, and unknown sets were generated from these samples. Three out of five (60%) of the hairs analyzed produced full DNA profiles that were correctly matched to the standard sets. DNA analysis was inconclusive (partial or no DNA profile) for two out of five (40%) of the samples. In contrast, the microscopic comparison analysis correctly matched four out of five (80%) of the samples to the standard sets but mis-identified one out of five (20%) of the samples. These results reinforce the practice of preliminary microscopic hair examination in narrowing down a set of hairs for DNA analysis. Microscopic comparison analysis is sufficiently reliable to remain a rapid and inexpensive method for forensic hair analysis.

Gunshot residue particle velocity and deceleration

The velocity of over 800 gunshot residue particles from eight different sources was determined using high speed stroboscopic photography (spark gap light source). These particles were found to have an average velocity of 500 to 600 ft per second. Many particles acquired considerably higher velocities. Thus, the particles have sufficient energy to embed themselves within certain nearby targets like skin or fabric. The relatively high velocity that the particles acquire explain the formation of stippling on skin in close proximity to a muzzle discharge. These findings also indicate little influence of air currents on particle behavior near the muzzle. The deceleration of less than 100 particles during a 100-microsecond interval was also calculated. The particles experienced rapid rates of deceleration which would explain why few particles are found in test firings beyond 3 ft from the muzzle of a discharged firearm. Because of their relatively high velocity, normal wind velocity would not be expected to significantly influence their motion near the muzzle.

Proximal End Root Morphology Characteristics in Antemortem Anagen Head Hairs

The proximal end morphology of antemortem anagen head hair was compared with the characteristics documented to occur in postmortem hairs. Antemortem anagen and telogen head hairs (N = 967) were recovered following exposure to seven environments. Root morphology characteristics consistent with those reported in postmortem hairs were observed in 66 (14%) hairs exposed to a water, normal saline, outdoor soil, or indoor shower environment. Thirty‐three anagen hairs (7%) exhibited a root band at the proximal end. The mean distance from the root tip to the onset of the root band ranged from 0.23 to 0.7 mm, depending on the environment. The mean distance from the root tip to the onset of the root band was 0.46 mm, with a mean band length of 0.44 mm. The results illustrate the need to better characterize postmortem banding through quantitative measurements, including the range for root tip to band distance and the overall band length.

Commentary on “3D bloodstain pattern analysis: Ballistic reconstruction of the trajectories of blood drops and determination of the centres of origin of the bloodstains” by Buck et al. [Forensic Sci. Int. 206 (2011) 22–28]

This commentary is in response to an article recently published in this journal by Ursula Buck, Beat Kneubuehl, Silvio Nather, Nicola Albertini, Lars Schmidt, Michael Thali regarding 3D bloodstain pattern interpretation [1]. There are a number of points that we felt were necessary to discuss: Buck et al. state that ‘‘blood drops, which fly through the air, are from the ballistic point of view always spherical.’’ In order to support this assertion they cite Pizzola, De Forest and Roth from 1986 [2]. However, the latter authors never made such a claim. In contrast, Pizzola et al. brought to the attention of the forensic science community the fact that much research had been done with aqueous droplets that demonstrated that they were very often not spherical but instead described as ‘‘cap cyclides’’ or ‘‘oblate spheroids,’’ et cetera [2,3]. Many researchers have studied aqueous droplets experimentally and have reported that even under relatively gentle conditions, as in free fall, that they will often manifest a somewhat flattened base in opposition to the direction of travel resulting from air resistance [4–7]. Not unexpectedly, the flattening effect is more pronounced with larger droplets. A flattened base is very different aerodynamically from a spherical one. Thus, one should not expect blood droplets of all sizes to be spherical when they are projected horizontally under initially much more energetic conditions compared to that in free fall. Based on the reports by James et al. [8] and Bevel et al. [9] Buck et al. stated that the diameter of drops is generally between 1 and 3 mm arising from blunt force trauma. In this context, it is not clear if Buck et al. are talking about drop diameters or resulting stain diameters. The James citation does not really clarify this question. James stated ‘‘The size of individual bloodstains produced is usually within the range of 1 to 3 ml [sic] in diameter although smaller and larger bloodstains are not uncommon’’ [8]. The abbreviation ‘‘ml’’ obviously signifies ‘‘milliliter’’ although it is apparent that this is a typographical error and James really meant to indicate ‘‘mm.’’ However, what is clear is that James stated that it was not uncommon to find both larger and smaller bloodstains. If it is not uncommon to find stains having diameters both larger and smaller is it reasonable for Buck et al. to state that in general drop diameters (as opposed to stain diameters) are generally between 1 and 3 mm? Many of the stains produced from blunt force trauma have been found by Laber to be larger [10]. It is interesting to note that James had reported earlier that stains produced by this mechanism are ‘‘usually within the range of 1–4 mm in diameter although smaller and larger bloodstains are not uncommon.’’ [11]. A fundamental premise of the Buck et al. paper is that the mass of a drop can be reasonably approximated from the width (minor diameter) of the resulting stain pattern. They cite Carter (1999, p. 20)

An Alternative Method to Screen for Pepper Spray Residue

A method was developed to screen for pepper spray residue using instruments and methods other than those techniques commonly employed to analyze chemical residue (i.e.. gas chromatography mass spectrometry-GCMS or liquid chromatography mass spectrometry-LCMS). The method employed gas chromatography (GC), thin layer chromatography (TLC), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to screen for dried pepper spray stains. Pepper sprays from nine different manufacturers were investigated. Capsaicin and dihydrocapsaicin were identified and unique IR reflectance spectra are presented. An additional five compounds were presumptively found. Results showed that a particular stain could be characterized as a pepper-based stain.