Paint & Coatings Industry - November 2008 - (Page 75)

Science A significant amount of time is spent in perusing current industrial literature, like PCI, and research journals, and then requesting samples and analyzing new materials. In the case of paint, these materials include resins, pigments, fillers, additives and sample paint panels, as well as MSD sheets and patent information. It’s not unusual to characterize and database analytical results on one or two new products each day. The fundamentals of forensic paint analysis are covered by ASTM Guideline E 1610, in volume 14.02. The characterization normally involves infrared spectrometry (FTIR), electron microscopy-x-ray spectroscopy (SEM-EDS and WDS) elemental analysis, pyrolysis-gas chromatography-mass spectrometry (PGC-MS), colorimetry and refractive index determinations. Dyes are further analyzed by thin layer chromatography (TLC). Some labs include x-ray diffraction (XRD) in their analytical scheme. It’s a time-consuming process, but it’s difficult to identify things we’ve never seen before. impression in the frame. Suddenly, the detective had definitive evidence to work with, largely due to his thoroughness. The association is shown in the photo. Case Example Two At the other extreme in paint examinations is a case that grew out of an accident investigation involving a run in between a passenger car and a tractor-trailer rig. The tractor driver insisted that the car, traveling to his right, cut in front of him and its left-rear fender clipped his right front wheel, causing the car driver to lose control and spin off the highway. The car driver, on the other hand, insisted that the tractor veered right into his car’s left-front fender and caused the accident. The car was old, poorly cared for, and exhibited extensive damage on all quarters. Paint fragments were collected from the tractor’s right front wheel lugnuts, and the left front and left rear fenders of the car. Subsequent analysis showed that the front of the car exhibited 14 layers of paint, and the rear, 13 layers. The missing layer at the rear of the car was layer number 8 on the front. A description of all the different paint chemistries encountered is beyond the scope of this short piece, but suffice it to say, the lug-nut samples exhibited 13 layers, and the trucker’s story was found to be true. The car driver was stuck with having to buy and pay for his own, much needed, new car. His existing insurance didn’t cover much. Observation is Key “Opportunistic observation” can be a key phrase in forensic paint examinations. Detectives can’t be expected to request analyses of things they can’t see, so trace examiners need to keep their microscopical eyes open for valuable evidence the detectives might legitimately miss. Case Example One A case in point involved another burglary that was possibly associated with a red-handled hatchet, used as a prying device to open a locked window. Once again, the request held little hope of leading to a definitive report and, indeed, the finding of similar red lacquer on the window frame and hatchet handle was hardly a unique piece of evidence. Fortunately, the detective in the case had been thorough, and had collected and submitted as many pieces of damaged framing as he could find. Close examination, under relatively low magnification, showed that a small, half-inch long, damaged fragment of the red paintsmeared frame also exhibited elongated impressions. Examination of a damaged paint area of the hatchet handle showed exposed wood grain that matched the Case Example Three Not all criminal trace analyses lead to convictions. They can also lead to the exoneration of suspects or previously convicted persons. A case in point is one where a woman was in a pickup truck with her boyfriend and his brother, going the wrong way on a city freeway. They hit three other cars, and a woman in one of the cars died of her injuries. Two county attorneys at the scene, along with accident investigators, accepted the story of the boy “friend” and his brother that the very intoxicated girl friend was driving. Erroneous, or perhaps presumptive, analyses by blood spatter experts, serologists and accident reconstructionists, supported the men’s stories. The girlfriend was poor, could not post bond and spent nine months in jail waiting for a trial. A defense investigator later questioned the blood spatter work, and all the physical evidence in the case, PA I N T & C O A T I N G S I N D U S T R Y 73

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Paint and Coatings Industry - November 2008 Contents Viewpoint Industry News Calendar of Events Company News Mergers and Acquisitions Names in the News HiTone Resins for Enhanced Pigment Affinity of Powder Coatings New Water-Based Interior Coatings Combine Innovation and Quality With Respect for the Environment Novel, UV-Curable Nanotechnology-Enabled Coatings Highly Weather-Resistant Radiation-Curable Monomers and Oligomers for Exterior Applications Konica Minolta — Sensing Success for Viracon Self-Crosslinkable Thermosetting Acrylics for Use in Water-Dilutable Coatings Paint and Criminal Forensic Science Supplier and Application/Curing Showcases Materials Watch Classifieds Advertiser Index

Paint & Coatings Industry - November 2008

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