飞纳台式扫描电镜在法医鉴定领域的应用

FORENSIC LABORATORY-IMAGING DESKTOP SEM FORENSIC APPLICATIONS WITH PHENOM The first“Point and Shoot”desktop SEM Applications laboratoryEindhoven， The Netherlands Light microscopy Scanning electron microscopy Affordable in price Centrallab High sample throughput High price Limited maximummagnification and depth oftocus Specialized facilities Dedicated operator ·Low sample throughput Robust Very high magnification and depth oftocus Optical image of Diatoms at 1000x SEM Image of Diatoms at 1000x ELECTRON MICROSCOPE MAGNIFICATION DEMAND 10x 100x 1，000x 10，000xMagnification 100，000x PHENOMWORLD Fills the gap between quality optical microscopes and low end SEM Affordable price High magnification and depth of focusUser friendlv PHENOMWORLD lmages within 30 seconds ·FPatented sample loading technology G2 pro ‘Never Lost Navigation' 回 Anyone can use it·Training in less than 1 hour Superior Imaging 45kX magnification with high depth of focusSits on a desk FPlugs into a standard outlet Benefits forensic SEM users Increased throughput for imaging and analysis Maximum field-of-view of6 um Available and use-able for every lab-user Forensic Light microscope users Require increased magnification due to shrinking features of interest Benefits of high depth of focus As easy to operate as an optical microscope The list below contain a number of typical forensic applications examples forSEM. These are all potential applications suitable for Phenom. A few examplescan be seen in the next slides. Gun Shot Residue (GSR) Traffic accidents Crime scene investigation Detecting of asbestos in imported materials Characterizing micro controllers (manipulated credit cards) Documents forgery (paper and ink) Identification of security items on treasury notes and passports Drug crime， toxic substances， pharmaceutical crime Tool marks Gunshot residue (GSR) is principally composed of burned and unburned particles from the explosive primer， the propellant， as wellas components from the bullet， the cartridge case and the firearm used. GSR is the residue that gets deposited on the hands of theshooter after the bullet has been fired. GSR can be very helpful in connecting the firearm to the culprit，establishing the identity ofthe shooter and in some cases may help in eliminating the probability when the number of suspect is more. Detection of asignificant amount of residue，therefore， is a powerful piece of forensic evidence that the particular person was very near to， evenholding， the gun when it discharged. Particles containing lead， antimony and barium are considered characteristic of GSR. The most definitive method to determine if aparticle is characteristic of or consistent with GSR is by its elemental profile. Particle analysis by a scanning electron microscopeequipped with an energy dispersive X-ray spectroscopy detector (EDS) can be the most powerful tool for forensic scientists todetermine the proximity to a discharging firearm and/or the contact with a surface exposed to GSR. The image shows a potentialGunShotResidue particle. GSR particles can quite easily berecognized due to the compositionalinformation of the Phenom backscatter detector. The particle can be further analyzedby using the Phenom’s EnergyDispersive X-Ray Detector (EDS). GSR ANALYSIS PHENOM The screenshotshows the EDS spotanalysis results fromthe particle via thespectrum peaks andthe output tablecontaining theelements and weightpercentage. Via ElementIdentification， theparticle has beenidentified as GunShot Residue due tothe presence of Lead(Pb)， Antimony (Sb)and Barium (Ba). PHENOMWORLD GSR ANALYSIS PHENOM The screenshot showsan EDS analysis of gunpowder (gun： dagsx9x19 np). Both the police in the Netherlands as in Germany useGadolinium in their gunpowder to easilyrecognize them. The electron image isshown at the right topside. The Gd peak can clearlybe seen in the spectrumat 6.056 keV. The weightpercentage is alsodisplayed in the outputtable (3.6%). PHENOMWORLD Scanning Electron Microscopy (SEM) is often used in investigating forensic materials incase of a traffic incident with serious injury. It is possible to determine whether or not the headlights were turned on or if the indicatorwas in use during the moment of collision. The safety belt of a car will reveal whether ornot it was in use during the moment of impact. Animal hair found on the vehicle could bethe reason of causing a collision. Car paint flakes can be very useful in providing evidencefor hit and run accidents. When a car head- or rear light or indicator is on， thelamp filament will be hot and at the time of acrash， glass particles will melt onto the filament. 4268pm light bulb Tungsten filament with Glass particles EDS spot analysisclearly shows thepresence of SiO，(glass). The other 2 particlesthat can be seen in theimage have the samegrey level as theidentified glass particleand can be consideredas glass particles aswell. Material contrast basedon grey level is verypowerful when imagingwith the back scatterdetector. PHENOMWORLD Animal hair found on a car could be the cause of a so called“one vehicle”accident. Hairs are composed primarily of theprotein keratin and can be defined as slender outgrowths of the skin of mammals. Each species of animal possesses hairwith characteristic length， color， shape， root appearance， and internal microscopic features that distinguish one animalfrom another. The images below have been taken with the charge reduction sample holder which makes it possible toimage these non conductive hair in their original state (no sputter coating required). < 134 pm hair cat hair dog Hair of a cat Hair of a dog PHENOMWORLD After a hit and run accident， often small car paint flakes can be found at the crime scene.Car paint consists ofdifferent layers of paint. Comparisons are made between flakes from a suspect vehicle and the specimen inorder to find a match. The picture shows a paint flake revealing various paint layers. The numbers represent Weight percentage Certainty 64.6% 98.2% 19.4% 97.7% PHENOMWORLD 99.1% The screenshot isshowing an overview ofthe car paint flake thathas been mapped.Elemental mappingreveals the distributionof the different elementswithin the sample. Thedifferent elements canbe highlighted viacolouring. A crime scene can contain microscopicsamples like hair， diatoms， pollen etc. whichcan be identified with electron microscopes. Forensic hair analysis can be used for： Identifying criminal suspects Identifying crime victims Associating a victim or suspect with a location Determining the type of crime committed Hairs can be transferred during physical contact， their presence can associate asuspect to a victim or a suspect/victim to a crime scene. The types of hair recoveredand the condition and number of hairs found all impact on their value as evidence ina criminal investigation. Comparison of the microscopic characteristics of questionedhairs to known hair samples helps determine whether a transfer may have occurred. In humans， hairs found on the head， pubic region， arms，legs， and other body areashave characteristics that can determine their origin. Most information can be derivedfrom head hair. Differences in cross section， the outer layer (cuticle)， central canaletc. can say something about the persons origin (African， European， Asian). Hair European origin including a pointto point measurement made withPhenom. Hair Asian origin Diatoms are unicellular organisms that live in open water. Diatom analysis can be of further use in forensicscience through identifying the provenance of individuals， clothing or materials from sites of investigation.In cases of drowning， the inhalation of water causes penetration of diatoms into the system and blood stream，and thus， their deposition into the brain， kidneys， and other organs. If the victim was dead before a body wassubmerged， the transport of diatom cells to various organs is prevented because of a lack of circulation. The type of diatoms that have been found can be used to pinpoint the location of where the drowning occurred.The presence of specific diatoms in the cloth of a body can tell if a body has been moved. Diatoms generally range in size from ca. 2-200um which can make it difficult to recognize them withlight microscopy. Desktop SEM is the perfect solution due to higher magnification and depth of focus.Sample preparation is similar to optical devices. Pollen is a fine to coarse powder containing the micro gametophytes of seed plants. Pollen grains come in allshapes and sizes and they never decompose. Pollen can tell a lot about where a person or object has beenbecause specific locations can have a distinctive collection of pollen species. Pollen evidence can also reveal theseason in which a particular object picked up the pollen. For instance， a dead body may be found in a wood， andthe clothes may contain pollen that was released after death， but in a place other than where it was found. Thatindicates that the body was moved. pollen Birch pollen grass pollen PHENOMWORLD Most crimes are committed using a variety of tools such as knives， crow bars， screw drivers and wire cutters. Whencriminals use these tools to commit a crime they can leave behind marks or damage to the material they come into contactwith. The marks made are generally lines (called Striations) and are caused because of imperfections on the surface of the tool. cable As shown above， the back scatter imaging detector inside the Phenom can be used in 2 modes：1) Compositional mode (full mode). This gives maximum signal resulting in materialinformation by means of contrast differences. Different materials can be recognizedbased on the grey scale level (left side image). 2) Topographical mode. This gives a different kind of shading resulting in a topographicalimage (3D effect). Using this mode the surface structure is more clearly visible. Like a cutting tool， a knife will also show unique marks after usage. Fiber ends from textile which have been cut by a knife. Image1 Image 2 Save project In the 20th century asbestoshas often been used inconstruction materials. Forensic investigation ofsuspected asbestos-relateddeaths includes a life-timeoccupational history， acomplete autopsy， andidentification of theasbestos fiber tissueburden. The screenshot shows thePhenom EDS analysisresults from crocidolite， alsoknown as“blue asbestos”. PHENOMWORLD bHEIIOIVMOBD PHENOMWORLDVer. .， Feb. PHENOMWORLD