Biomedical subjects

Valerio Causin

Publications and source records attributed to Valerio Causin.

8 recordsLinked to original sources

PubMed2006

A quantitative differentiation method for plastic bags by wide angle X-ray diffraction for tracing the source of illegal drugs.

Thirty-three shopping bags, commonly encountered in the packaging of drug doses, were characterized by wide angle X-ray diffraction (WAXD). Using this single technique, without sample preparation, nearly all the considered samples could be differentiated, achieving a discriminating power of 0.992. The rather large degree of variability existing in grocery bags, even though they are mass produced, was shown, confirming that these items can be useful in tracing the source of illicit drug doses.

Journal Article↗

PubMed2006

A quantitative differentiation method for plastic bags by infrared spectroscopy, thickness measurement and differential scanning calorimetry for tracing the source of illegal drugs.

Fifty shopping bags, commonly encountered in the packaging of drug doses, were characterized by thickness measurements, infrared spectroscopy and differential scanning calorimetry. By these very straightforward and inexpensive techniques, without sample preparation, nearly all the considered samples could be discriminated. Ninety-seven percent of the possible pairs of white, apparently similar dull polymer films were differentiated. The rather large degree of variability existing in grocery bags, even though they are mass produced, was shown, confirming that these items can be useful in tracing the source of illicit drug doses.

Journal Article↗

PubMed2005

A quantitative differentiation method for acrylic fibers by infrared spectroscopy.

Absorbance peak areas of nitrile (2240 cm(-1)), carbonyl (1730 cm(-1)) and CH (1370 cm(-1)) groups were obtained for 48 colorless acrylic fibers by infrared (IR) microspectroscopy. The carbonyl signal, related to the comonomers most commonly used in acrylic fibers, was ratioed against the nitrile and CH bands, pertaining to the backbone of the polymer chains. The ratios A1730/A2240 and A1730/A1370, a relative measure of the comonomer content in the fiber, were used to differentiate the samples. A decrease in the crystallinity of fibers has been noted with increasing comonomer content. Relative standard deviation (R.S.D.) of the ratios were 1 and 3% for repetitive analyses on the same location and along the length of the same single fiber, respectively. When different fibers of the same sample were examined, results were reproducible within 6%. This simple method can greatly enhance the evidential value of colorless acrylic fibers, being able to discriminate them and thus helping the Court to better assess their significance.

Journal Article↗

PubMed2005

Employing glass refractive index measurement (GRIM) in fiber analysis: a simple method for evaluating the crystallinity of acrylics.

The refractive index (RI) of 40 colorless acrylic fiber samples was determined by the immersion oil and Mettler hot stage method, implemented in the glass refractive index measurement (GRIM) instrument by Foster and Freeman. Low standard deviations for nearly all the samples were obtained and differentiation of fibers even with the same trade name was possible just on the basis of RI. Wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) were employed to establish a linear correlation between RI and the degree of crystallinity. Insights on the structural order of this group of fibers is then obtainable by a quick and easy technique, adding value to casework comparisons.

Journal Article↗

PubMed2005

Cuts and tears on a paper towel: a case report on an unusual examination of damage.

The examination of damage to a paper towel, an item of evidence in a murder case, is described. Simulations performed with selected tools and the observation of the lacerations present on the towel permitted to infer that they were originated by cleaning of a pointed and sharp implement. Some marks, considered characteristic of scissors, were detected on the exhibit. This experimental outcome resulted critical in challenging the declarations of the suspect. A rather significant analogy between damage examination on paper towels and on textiles was established.

Journal Article↗

PubMed2005

The effect of exposure to the elements on the forensic characterization by infrared spectroscopy of poly(ethylene terephthalate) fibers.

Validation of a recently proposed differentiation method for single poly (ethylene terephthalate) (PET) fibers, based on integration of IR absorption bands, is presented. IR microscopy in the transmission mode, differential scanning calorimetry and optical microscopy were employed. The reliability of the technique has been extended to the cases in which the fibers being compared have experienced long exposure to the elements, as may happen if these items are recovered from open-air crime scenes. The effect of immersion in water and irradiation by the sun for a three-month period have been considered. The fibers remained morphologically and structurally unaltered. The significance of comparisons between fibers kept in different environments is thus enhanced, because the detrimental effect of the elements can be ruled out. This further validation of the proposed technique contributes to render the data presented by the forensic scientist less vulnerable to context effect and bias.

Journal Article↗

PubMed2004

Bayesian framework for the evaluation of fiber evidence in a double murder--a case report.

Fiber evidence found on a suspect vehicle was the only useful trace to reconstruct the dynamics of the transportation of two corpses. Optical microscopy, UV-Vis microspectrophotometry and infrared analysis were employed to compare fibers recovered in the trunk of a car to those of the blankets composing the wrapping in which the victims had been hidden. A "pseudo-1:1" taping permitted to reconstruct the spatial distribution of the traces and to further strengthen the support to one of the hypotheses. The Likelihood Ratio (LR) was calculated, in order to quantify the support given by forensic evidence to the explanations proposed. A generalization of the Likelihood Ratio equation to cases analogous to this has been derived. Fibers were the only traces that helped in the corroboration of the crime scenario, being absent any DNA, fingerprints and ballistic evidence.

Automobiles↗

PubMed2004

Forensic analysis of poly(ethylene terephthalate) fibers by infrared spectroscopy.

Poly(ethylene terephthalate) (PET) is one of the most commonly employed polymers in the textile industry. Its relevance as a source of evidence in the reconstruction of criminal cases is nevertheless very limited because the properties and morphologies of fibers from different producers tend to be very similar. By integrating bands, obtained on single fibers by infrared (IR) microscopy, associated with trans and gauche conformation and to the O-H end-groups of the molecules, a method is proposed that can discriminate otherwise similar PET fibers. The absorbancies at 1370 and at 846 cm(-1) relative, respectively, to the gauche and trans conformation, were measured and ratioed. The end-group content was evaluated by ratioing the absorbancies of the signals at 3440 and at 874 cm(-1). Relative standard deviation (R. S. D.) was 1% for repetitive analyses on the same location of the same single fiber. Precision was reduced if the ratios were measured along the length of a single fiber (R. S. D. = 3%) and even further when different fibers of the same sample were examined (R. S. D. varied from 2 to 10%). This simple method can greatly enhance the evidential value of PET fibers by subclassifying them, thus helping the Court to better assess their significance.

Calorimetry, Differential Scanning↗