Classifying single fibers based on fluorinated surface treatments.

Fibers are an important form of forensic evidence, but their evidential value can be severely limited when the identified characteristics of the fibers are common, such as blue cotton. Detecting chemical fiber treatments offers an avenue to further classify fibers and to improve their evidential value. In this report, we investigate the potential of fluoropolymer fiber coatings, used to impart oil and water-repellent properties in fabrics, for differentiating between fibers. The thin nature of these fiber surface modifications creates an analytical challenge for their detection on a single fiber, a typical sample size for forensic evidence. Specifically, pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) has shown promising selectivity but the sensitivity of the method is not adequate for single-fiber analysis of fluorinated coatings. To overcome this challenge, we utilize a newly developed elemental ionization source, plasma-assisted reaction chemical ionization (PARCI). The high sensitivity of py-GC-PARCI-MS for elemental fluorine analysis offers selective and sensitive detection of fluorinated pyrolysates among the non-fluorinated pyrolysates of the fiber core. As a result, fluoropolymer coatings are detected from 10-mm single-fiber samples. The technique is applied for classification of 22 fiber types, resulting in 4 distinct groups via hierarchical cluster analysis based on similarity of fluorine pyrograms. These results present the first study to classify fibers based on fluorinated coatings, and highlight the potential of py-GC-PARCI-MS for forensic analyses. Graphical Abstract ᅟ.

Spectroscopic imaging based approach for condom identification in condom contaminated fingermarks.

Sexual offenders are increasingly reported to use condoms while committing the crime, mainly to prevent the transfer of DNA evidence. Although condoms are often removed from the crime scene, vaginal swabs can be taken from the victim to prove the presence of condom lubricants and therefore evidence of corpus delicti. However, late reporting to the police and the tendency of the victim to wash immediately after the crime, may compromise the detection of condom lubricants. Recently we showed that Matrix-Assisted Laser Desorption/Ionisation MS Imaging (MALDI MSI) of condom contaminated fingermarks enables images of the fingermark ridge pattern to be obtained simultaneously with the detection of the condom lubricant for two condom brands, thus becoming a potential alternative way to link the assailant to the crime. Building on the value of this information, it would be advantageous to identify the condom brand used during the sexual assault. Here we show the development of a multidisciplinary spectroscopic approach, including MALDI MSI, MS/MS, Raman microscopy and ATR-FTIR spectroscopy, applied to a range of condom brands/types. The techniques have complementary features and provide complementary information to retrieve a "condom brand spectroscopic fingerprint". Unique spectroscopic profiles would greatly aid in the screening and identification of the condom, thus adding intelligence to the case under investigation.

Analyzing forensic evidence based on density with magnetic levitation.

This paper describes a method for determining the density of contact trace objects with magnetic levitation (MagLev). MagLev measurements accurately determine the density (± 0.0002 g/cm(3) ) of a diamagnetic object and are compatible with objects that are nonuniform in shape and size. The MagLev device (composed of two permanent magnets with like poles facing) and the method described provide a means of accurately determining the density of trace objects. This method is inexpensive, rapid, and verifiable and provides numerical values--independent of the specific apparatus or analyst--that correspond to the absolute density of the sample that may be entered into a searchable database. We discuss the feasibility of MagLev as a possible means of characterizing forensic-related evidence and demonstrate the ability of MagLev to (i) determine the density of samples of glitter and gunpowder, (ii) separate glitter particles of different densities, and (iii) determine the density of a glitter sample that was removed from a complex sample matrix.

Characterization of multilayered glitter particles using synchrotron FT-IR microscopy.

Multilayered glitter particles were cut with a microtome into thin cross-sections and examined using an FT-IR microscope with a synchrotron infrared source. The high brightness of the synchrotron source enabled high-quality infrared spectra to be quickly obtained from individual layers in the glitter particle cross-section, providing additional chemical information that could increase the glitter particle's value as associative evidence in criminal cases.

A novel matrix-assisted laser desorption/ionisation mass spectrometry imaging based methodology for the identification of sexual assault suspects.

An increase in the use of condoms by sexual offenders has been observed. This is likely to be due both to the risk of sexually transmitted diseases and to prevent the transfer of DNA evidence. In this scenario the detection of condom lubricants at a crime scene could aid in proving corpus delicti. Here we show a novel application of Matrix-Assisted Laser Desorption/Ionisation Mass Spectrometry Imaging (MALDI MSI) for mapping the fingermark ridge pattern simultaneously to the detection of the condom lubricant within the fingermark itself. Two condom brands have been investigated to prove the concept. Condoms were handled producing lubricant-contaminated fingermarks. Images of the ridge pattern were obtained simultaneously to the detection of two lubricants, even several weeks after the fingermark deposition. The results therefore show the potential of MALDI MSI to link the suspect (identification through fingermark ridge pattern) to the crime (detection of condom lubricant) in one analysis. This would enable forensic scientists to provide evidence with stronger support in alleged cases of sexual assault.

Bad science: the instrumental data in the Floyd Landis case.

BACKGROUND: In 2006 Floyd Landis won the world's most prestigious bicycle race, the Tour de France. However, not many days after the race's conclusion it was released to the press that the Laboratoire National de Dépistage du Dopage (LNDD) had found Landis' urine after stage 17 positive for synthetic testosterone. METHODS: This review examines the instrumental data and methodology used by LNDD in the Landis case. The conclusions reached by LNDD were based on results of 2 separate instrumental methods. Subsequent to urine extraction and possibly derivatization, samples were initially screened via gas chromatography/mass spectrometry (GC/MS) using selected ion monitoring (SIM) to measure the ratio of testosterone to epitestosterone (T/E). Final confirmation of exogenous testosterone was determined by measuring the (13)C/(12)C stable isotope ratios in 4 metabolites of testosterone via gas chromatography combustion stable isotope ratio mass spectrometry (GC-C-IRMS). CONCLUSION: T/E ratios determined by LNDD in Landis' stage 17 urine were unreliable due to the combined factors of an unsatisfactory extraction, high GC background, failure to obtain baseline peak separation for epitestosterone, unreliable quantization of the epitestosterone peak due to both peak overlap and because it was barely above background noise, and because only a single ion mass (432) rather than a minimum of 3 was used for SIM (in violation of both LNDD's SOP and WADA procedures). GC-C-IRMS methodology is less well known to the analytical chemistry community, but here too the results obtained by LNDD were unreliable. GC-C-IRMS errors can be briefly summarized as uncertain peak identification, unsuitable standards, and unreliable (and possibly biased) calculation of (13)C/(12)C ratios due to peak overlap as well as LNDD's usage of manual peak integration rather than use of the instrument system software.

Visualization of gunshot residue patterns on dark clothing.

Determination of the muzzle-to-target distance is often a critical factor in criminal and civil investigations involving firearms. However, seeing and recording gunshot residue patterns can be difficult if the victim's clothing is dark and/or bloodstained. Trostle reported the use of infrared film for the detection of burn patterns. However, only after the film is developed are the results visible and multiple exposures at different settings may be needed. The Video Spectral Comparator 2000 (Foster & Freeman Ltd., Evesham, Worcestershire, U.K.) is an imaging instrument routinely used by forensic document examiners. Without use of specialized film could the VSC 2000 (at appropriate instrument settings) quickly, easily, and reliably provide instantaneous viewing, saving, and printing of gunshot residue patterns on dark and/or blood soaked clothing? At muzzle-to-target distances of 6, 12, and 18 in., test fires were made into five different types of dark clothing using eight different handguns of different calibers. Gunshot residues were detected for all eight calibers, and powder burn patterns were seen on dark clothing for all three target distances and calibers except 0.22 long rifle and 0.25 ACP. Bloodstains did not preclude the viewing of these patterns.

A case study on forensic polymer analysis by DIOS-MS: the suspect who gave us the SLIP.

New technology was used to identify traces of a commercial barrier/spermicide in evidence from a case of a man accused of rape of a minor. Examination of vaginal swabs performed by another laboratory had been negative for seminal fluid or other sources of DNA from the suspect and we were asked to examine the remaining swabs for any traces that might have originated from the commercial product. Encare consists of vaginal inserts having a suppository-like shape. They contain the spermicide, nonoxynol-9, in a matrix consisting of approximately two parts polyethylene glycol (PEG) 1000 to one part PEG 1450, plus minor inorganic components added to produce foaming. Portions of the cotton from vaginal swabs from the victim and penile swabs from the suspect were extracted with methanol and subsequently examined by desorption ionization on silicon time-of-flight mass spectrometry (DIOS TOF MS). Low levels of PEG in the same mass range as Encare were found on two separate vaginal swabs from the victim and one penile swab from the suspect. Subsequent to these findings, the suspect (through his attorneys) provided us with a sample of SLIP Plus, a commercial sexual lubricant that also contains nonoxynol-9. Traces of PEG in the same mass range as Encare were found in this sample, while no PEG was found in a sealed sample of SLIP Plus provided by the manufacturer. At trial the suspect's attorneys stipulated that their client had added some Encare to the SLIP Plus sample he had provided.