xrd in forensic science from rigaku journal

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Introduction

The task of identifying an individual sus-pected of involvement in a crime usually comesdown to answering the question “Are the ac-cused person and the person characterized ashaving committed the crime in fact one and thesame person?” The question may be answeredin one of two ways: (a) it may be possible to es-tablish a connection between some physical ev-idence associated with the crime and some per-sonal characteristic of the accused e.g. his DNAprofile, his fingerprints, or a video surveillancecamera image of him, and (b) it may be possi-ble to show a connection between the scene of the crime and something which is definitely

linked with the accused e.g. textile fibres fromhis clothing, tool marks made by a case openeror screwdriver belonging to him, or hisshoeprints.

Of these two ways of answering the originalquestion, the former tends to provide the morecompelling evidence. DNA profiling yields nearunequivocal identification of an individual, anda clear fingerprint left at a scene is also one of the most reliable forms of evidence. If the per-petrator of the crime is careless or unfortunateenough to leave a body fluid or fingerprints atthe scene, there is a good chance of him beingapprehended. Alternatively, a high quality videocamera image of the individual’s face at thescene may result in his rapid identification,without the need for the expense of DNA profil-ing or for a fingerprint search.

There will be occasions, however, when thereis no photographic, DNA, or fingerprint evi-dence available, and the task of identifying orexonerating the accused may rely upon analysisof contact trace evidence. The oft-quoted guid-ing principle in forensic science is that “. . . everycontact leaves a trace...” so if we can identify

the trace, we provide evidence of the contact.Simple examples might be the collision of a redcar with a blue car, in which blue and red paintwill be transferred from one car to the other,and the transfer of clothing fibres from assailantto victim and vice versa during an assault.

X-ray diffraction (XRD) in forensic science[1–4] usually implies the use of powder diffrac-tion as opposed to single crystal diffraction. Thelatter is rarely used, because full structuralanalyses are seldom required, and the expenseof maintaining or leasing a facility for this pur-pose could not be justified. Qualitative phaseanalysis of polycrystalline organic, inorganicand metallic substances is the bread and butter

of the forensic diffractionist, who may be deal-ing with anything from microgram specimensto kilogram seizures of drugs. XRD is concernedlargely with the identification of these so-called“contact traces”. As might be expected, thereare many types of material (Table 1) which

THE RIGAKU JOURNALVOL. 19 / NO. 2 & VOL. 20 / NO. 1 / 2003

Vol. 19 No. 2 & Vol. 20 No. 1 2003 11

X-RAY DIFFRACTION IN FORENSIC SCIENCE

DAVID F. RENDLE

Forensic Science Service, London Laboratory, 109 Lambeth Road, London SE1 7LP, United Kingdom.

X-ray powder diffraction (XRD) is used widely in forensic science. Its main strengths are itsnon-destructive nature, thus preserving evidence, its ability to identify compounds and not justelements, and its ability to analyse many types of different materials—organic, inorganic andmetallic. A selection of evidence types and their analysis by XRD is described.

Table 1. List of materials examined by XRD.

Building materials (cement, mortar, concrete,plaster, fillers, bricks, putty)

Soils

Drugs (drugs of abuse together with their excip-ients and adulterants)Metals and alloysPaintsPapersPigmentsCosmeticsSafe ballastsMineralsPlastics and polymersSoap powders and detergentsAutomobile undersealsExplosives and gunshot residues



occur as contact traces and which can beanalysed satisfactorily by XRD. The only prereq-uisite is that the material should be crystallineor at least partially crystalline.

This is a comprehensive list showing the dif-ferent types of materials which at one time or

another have been analyzed by XRD in variousforensic science laboratories. Users of XRD inprivate industry, or for that matter in academiccircles, may concentrate on just one of thetypes of materials listed here, whereas theforensic analyst may be called upon to analyseany of these materials. A brief discussion fol-lows, in which the examination of a selection of these materials (paints/pigments, plastics/poly-mers, metals/alloys, drugs, paper, miscella-neous) is described, some illustrated with suit-able examples.

The choice has been made to reflect the ver-satility of XRD, because it can be used toanalyse all crystalline material, from organiccompounds such as drugs, through minerals, toheavy metals. As a general rule, a diffractionistin a forensic science laboratory will be asked toeither (a) identify a single substance e.g. a pow-der found on someone suspected of carrying re-stricted substances, or (b) compare two speci-mens to see whether or not they could havecome from the same source e.g. paint flakesfrom a window sill (control), and paint flakesfrom the clothing of a person suspected of hav-

ing gained unlawful entry through that window(suspect).Most contact trace specimens encountered in

forensic science are very small, so the XRD in-strumentation must be capable of small speci-men analysis. This can mean samples weighinga few microgrammes (m g). Powder photographywas always the method of choice for such smallsamples until latterly, when powder diffrac-tometers truly capable of small specimen analy-

sis (capillary-focused parallel beams and highresolution area detectors) became available.The types of powder cameras deployed areDebye–Scherrer (57.3 and 114.6mm diameter),Guinier, and Gandolfi. The Gandolfi camera isespecially suited to the analysis of materials

which for one reason or another cannot, orshould not, be ground up—for example, veryhard abrasive materials, gemstones, explosives,and materials that convert from one polymor-phic form to another on grinding [5–10].

Figure 1 gives an idea of the actual size of specimens, and the way in which they aremounted for examination in a Debye–Scherrerpowder camera. Paint flakes (or any monolithicspecimens) are mounted on the end of glass fi-bres, whilst powders are sealed inside thin-walled glass capillary tubes. Here, the loosepaint flakes weigh 150 and 30 m g and the brassspecimens 500 and 200 m g respectively.

The analysis of examples of the six types of materials described earlier now follows—paints,polymers, metals, drugs, papers and others.

Paints and Pigments [11,12]

When a case is submitted to the laboratory, itis assigned to one scientist who will decide onhow best to tackle the case and answer the in-vestigating officer’s questions. If paints are in-volved, for example in a typical break-in or roadtraffic accident, the first step is to compare con-trol and suspect specimens visually—by eyeand by low power visible light microscopy. If they appear identical in colour, then their chem-ical composition must be checked, and this iswhere Fourier Transform Infrared Spectroscopy(FTIR) or XRD may be used.

As a rule, single layer control and suspectpaint flakes are sent in for analysis with the re-quest to compare them and to establishwhether or not they are similar according totheir diffraction patterns. Part of the comparisonnaturally involves identification of as many of the crystalline components as possible, either

by reference to the ICDD Powder Diffraction File[13], or to a local collection of standard refer-ence diffraction patterns.

Figure 2 illustrates the importance of a tech-nique such as XRD, because the two blue paints(ICI Royal Blue and ICI Admiralty Blue) are visu-ally identical, as are the two red paints (ICI Sig-nal Red and ICI Post Office Red)—this is termeda metameric match. ICI Royal Blue containsPrussian Blue as its main pigment, and ICI Ad-miralty Blue contains b -copper phthalocyanine.The red paints do have some similarities in

12 The Rigaku Journal

Fig. 1. Paint and brass specimens beside scale.



composition—ICI Signal Red contains cadmiumsulphide and barium sulphate with an organicpigment Monolite Fast Scarlet (Colour Index (CI)Pigment Red 3). ICI Post Office Red containscadmium sulphide with either CI Pigment Red48 or 52.

The XRD results obtained from the controlpaint samples (i.e. known source) are classified

in terms of the categories household, vehicleand other, and these categories are subdividedinto eight colours. The analytical results areadded to a small database of paint composi-tions as determined by XRD. The purpose of this database is to provide simple statistics onthe frequency of occurrence of a particular com-bination of pigments or extenders within agiven colour category. These statistics form thebasis of the so-called evidential value of the an-alytical results. For example, suppose twopaints (control and suspect) match each other indiffraction pattern. What is the significance of this match? If the paints contain only one crys-talline component e.g. rutile (titanium dioxide),which is very common in white gloss paints—the significance of the match and its evidentialvalue are low.

If, however, the paints contain maybe four orfive crystalline components, some of them un-usual, then the significance of the match and itsevidential value is high. Reference to a databasemay reveal that a particular combination of pig-ments and extenders occurs only once in, say,fifty red paints analyzed during the last seven

years. Frequently the resins in the paints are an-alyzed too, and in this respect the non-destruc-tive nature of XRD is very useful. The paint isfirst analyzed by XRD and is then examinedusing Pyrolysis Gas Chromatography (PGC) orby Pyrolysis Mass Spectrometry (PyMS), pro-viding information about both the crystallineand non-crystalline components before the

sample is destroyed.Polymers [11,14]

XRD was used in this laboratory to identifythe crystalline pigments and fillers present inelectrical wire insulation, without really payingmuch attention to the broader, more diffuse dif-fraction maxima from the polymeric material.As there are already a number of well-estab-lished techniques for the analysis of polymers,for example PyMS, PGC and FTIR spectroscopy,these methods, in the majority of cases, wouldbe employed before using XRD if a sample

were suspected of being polymeric. However,the non-destructive nature of XRD gives it a dis-tinct advantage over these other techniques,and henceforth considerable use was made of XRD for plastics/polymer analysis—mainly as ascreening technique.

Plastics and polymers, perhaps because of their physical appearance, are sometimesthought of as being non-crystalline, and insome cases this is true. However, the majorityof the more common polymers and plastics areat least partially crystalline, and therefore lend

Vol. 19 No. 2 & Vol. 20 No. 1 2003 13

Fig. 2. Diffraction patterns of paints from metameric matches.



themselves to analysis by XRD.The powder patterns shown in Fig. 3 of PTFE,

polypropylene, and low- and high-density poly-ethylene are typical of polymers, with broad,diffuse lines. If pigments were present in anyplastic item made of these polymers, their dif-fraction patterns would consist of much sharperlines than those of the polymers.

Two cases illustrate the use of XRD in poly-mer analysis:1. Some pieces of unknown material were

submitted for analysis and they yielded dif-fraction patterns similar to that of polyvinylchloride (PVC). PyMS then confirmed thepresence of a copolymer with a high PVCcontent.

2. A “crystalline” deposit was found on achair. The deposit was in fact found to belargely amorphous, but a weak diffractionpattern present matched that of polymethyl-methacrylate. The deposit was later identi-fied by PyMS as poly-methylcyanoacrylate.

Metals and alloys

Generally speaking, metals and alloys areidentified by elemental analysis, for exampleusing X-ray fluorescence (XRF) or by micro-probe analysis in the scanning electron micro-scope. However, these methods yield no infor-mation about the phases present, and this iswhere XRD is most useful.

One of the most frequently-encountered met-als in everyday life is brass [15], perhaps be-

cause its composition is so variable which givesrise to variable physical properties to suit differ-ent applications.

Figure 4 shows a phase diagram of the cop-per/zinc system. On the left is the a phase, asolid solution of zinc in copper ranging from 0to 38% zinc by weight. Next to this is the duplexphase (a b ), and further to the right is the b phase in the region of 50% zinc. Brasses of thetype a and (a b ) are the most common, whilst


Fig. 3. Diffraction patterns of a small selection of common polymers.

Fig. 4. Phase diagram of brass.



those with over 50% zinc are rarely used com-mercially on account of their brittle nature. Thetwo phases, a and b , have quite different crystalstructures. Alpha brass has a face-centred cubicstructure with continuously variable occupancyof each site by copper and zinc whilst beta

brass has a CsCl cubic structure with zinc at thecentre and copper at the corners.Figure 5 shows powder photographs of a se-

lection of different brass compositions. Thepowder pattern at the bottom of Fig. 5 standsout because it has two diffraction patterns on it,one from a brass and one from b brass. It is of aduplex 60/40 Cu/Zn brass, a common machinebrass. The remaining patterns are of pure alpha(a ) brass with varying Cu/Zn ratios. As morezinc is added, the unit cell expands and the ef-fect on the powder pattern is best seen by look-ing at the diameter of the 400 reflection in theback reflection region of these powder pho-tographs.

A rough estimate of the percentage of zinc ina single phase a brass may be obtained bystraightforward comparison of its powder pho-tograph with these standards. A more accurateestimate (1%) can be obtained by plotting unitcell dimensions versus %Zn for each of the purestandards.

The variation in composition of a number of common brass objects is quite surprising, andas a result they can be readily distinguished by

XRD analysis.Figure 6 shows a Yale lock, Yale lock retaining

ring, Yale lock cylinder, door keys (Chubb andYale), an electric light fitting, a wood screw,brazing rod, a .303 cartridge case and a cup-board hinge. Although all these items are madeof brass, the composition in each is different. Inaddition to identifying the phases of brass andproviding the % zinc in single phase a brasses,an estimate of the ratio of the a to b phaseswithin a duplex (a b ) brass can be made bymeasuring the relative intensities of the majorlines of these phases. The presence of lead (toimprove machinability) in some of the alloys isalso detectable.

Vol. 19 No. 2 & Vol. 20 No. 1 2003 15

Fig. 5. Powder diffraction patterns of a and (a b ) brasses. From the top: 85% Cu 15% Zn,80: 20 Cu: Zn, 70: 30 Cu : Zn, 65 : 35 Cu: Zn, and 60 : 40 Cu: Zn.

Fig. 6. Various objects made of brass.



An example of the use of brass analysis incasework was the attempted theft of a ship’spropeller. A worker in a small dockyard repairshop on the River Thames near Woolwich,south London had seen a tugboat propeller (Fig.7 below shows an example) being brought to a

neighbouring shop for repair. He decided tosteal the propeller and sell it for scrap. The pro-peller was four-bladed in cast brass, weighingapproximately a ton (950 kg) and measuring 5 ft(1.5 m) from blade tip to blade tip.

His plan was to enter the repair shop afterdark, cut the blades off the propeller with agasoline-powered abrasive disc cutter/grinder,and load the severed parts into the back of histruck and make off with them. Unfortunately heforgot to check how much gasoline he had in

the tank of the cutter/grinder, and before he hadeven cut through one blade of the propeller, thecutter ran out of gasoline. The man ran to histruck with the cutter/grinder and made off. Thenoise of the cutter had attracted attention andhe was seen by a witness who reported his ve-

hicle registration number to the police. Within10 min the police were knocking at the man’sdoor. They found him inside with his overallsoff, standing in jeans and a singlet, and fromthe neck up he was covered in a layer of finebrass particles—from the action of thecutter/grinder on the propeller blade. The manwas arrested and taken away. Samples of thebrass particles from his body and clothing, to-gether with a sample of control brass from theship’s propeller were submitted to the labora-tory for examination.

The powder photographs in Fig. 8, whichwere both of a duplex (a b ) brass, seemedquite different at first which was surprising, butreference to the phase diagram provided an ex-planation. The cutting action of the abrasivedisc on the metal would have generated a greatdeal of heat—probably raising the temperatureto 300–400°C, and brass particles at this temper-ature would have had their a / b phase ratioshifted in favour of the b phase. When bothsamples were annealed at 500°C, the resultingpowder patterns (Fig. 9) agreed very well in-deed.

Particles of abrasive material found on the


Fig. 7. Propeller of the type described in the caseabove.

Fig. 8. Powder photographs of brass from (a) the suspect’s clothing and (b) from the pro-peller.

Fig. 9. Powder photographs of annealed specimens of control and suspect brasses.



man’s clothing were compared with control gritfrom the cutter/grinder, and they were alsofound to be identical, consisting of silicon car-bide (SiC).

Drugs

It would be misleading to imply that all drugs

seizures are analysed by XRD alone, but a con-siderable amount of analytical data have beenamassed by forensic science laboratoriesaround the world [16–21]. Some of the drugsmost frequently encountered are cocaine,heroin, morphine and the amphetamines. Thesedrugs occur as loose powders or tablets inwhich the drug is mixed or “cut” with someother substance termed a diluent or adulterant(Table 2).

The initial examination is by eye and occa-sionally by low power visible light microscopy.

Simple chemical tests are then used to identifythe drugs present, and confirmation is by GasChromatography-Mass Spectrometry (GCMS). If the drugs present are to be quantified, this willusually be achieved with Nuclear Magnetic Res-onance (NMR), GCMS, or High PerformanceLiquid Chromatography (HPLC). FTIR is used todistinguish between cocaine base (Crack) andthe main salt of cocaine, cocaine hydrochloride.

XRD is usually employed (a) to identify theprecise chemical form (salt, base, acid) of thedrug, (b) to identify any diluents or adulterants,and (c) in some cases to compare one seizurewith another, or with several others. Theamount of a seizure can vary enormously, froma few milligrams to kilograms depending uponthe source. If XRD analysis is required, a sub-sample of a few milligrams is submitted to theX-ray Section once the initial examination hasbeen completed by the Drugs Section. Pow-dered specimens are hand-ground using anagate mortar and pestle, and for diffractometryare loaded into flat specimen holders using theside loading technique of McMurdie et al. [22].If powder photography is to be used, they are

loaded into thin-walled glass capillary tubes(0.3 mm diameter). Iron-filtered Cobalt Ka radia-

tion is used in the London Laboratory of theFSS. Its wavelength (1.79026 Å) provides betterangular dispersion than Cu radiation, at the ex-pense of intensity and count rates.

Identification of as many of the componentsas possible in a mixture can provide a wealth of

information, for example trends in usage of par-ticular drugs, changes in diluents or adulter-ants, and changes in the purity of a synthesizedproduct. These aspects may reflect changes insocial habits, changes in sources and suppliers,and demand for better, purer products respec-tively. Identification of the salt, base or acid of drugs such as cocaine (free base (Crack) and hy-drochloride), heroin (base and hydrochloride),morphine (base, hydrochloride and sulphate)are a matter of routine. Distinction between theoptically active form(s) and the racemic form of drugs such as amphetamine (d - or l -ampheta-mine sulphate and dl -amphetamine sulphate) isalso a relatively simple process by XRD. Powderdiffraction will not permit distinction of the d -form of any compound from its l -form, how-ever, and single crystal diffraction experimentswould be required for this. In some cases FTIRspectroscopy will distinguish salts from basesin high purity mixtures, but if the drug is mixedwith certain diluents, it may be impossible tostate with certainty whether the drug is presentas a base or salt.

Figure 10 shows three forms of amphetamine

salts which are easily distinguishable by XRD.The same applies to different forms of the othercommon drugs of abuse. Other salts exist, e.g.phosphates, tartrates, and citrates but they arenot seen as frequently as sulphates, hydrochlo-rides and the base forms of heroin, morphineand cocaine. XRD is an excellent way of identi-fying these and other forms of drugs, throughreference to the ICDD Powder Diffraction File(PDF) [13] or to a local database of patterns.

In general, sugars are the favoured adulter-ants, with Epsom Salts (MgSO4 · 7H2O) being themost common inorganic substance (see Fig.16). Useful information concerning syntheticroutes of drug manufacture may sometimes beobtained from XRD analyses. For example,Crack cocaine (cocaine base) may be preparedfrom its hydrochloride by heating with sodiumbicarbonate. The sole end products should becocaine base and sodium chloride, so the pres-ence of all four compounds in a seizure pointsto a rather amateurish, incomplete attempt atsynthesis from cocaine hydrochloride andsodium bicarbonate.

If a record is maintained of the diluents or

Vol. 19 No. 2 & Vol. 20 No. 1 2003 17

Table 2. List of common diluents/adulterants.

Mannitol (b , and occasionally Boric acida and d )

a -Lactose monohydrate Citric acidGlucose monohydrate Magnesium sulphateSucrose Sodium chlorideFructose Flour, talc



adulterants identified over a period of time,trends appear, and it is apparent that certaindiluents are preferred for particular drugs. Forexample, the favoured carbohydrate for am-phetamine sulphate appears to be glucosemonohydrate, whilst that for cocaine is b -d -

mannitol.In a particular case study, an off-white pow-der was submitted for analysis. The Drug Sec-tion’s preliminary analysis revealed heroin, glu-cose, and sodium chloride. A sub-sample wassubmitted to the X-ray Section with the requestto confirm this analytical result, and to identifythe chemical form of heroin, i.e. base or hy-drochloride.

The XRD result confirmed the presence of heroin (as the hydrochloride hydrate), and alsosodium chloride, but no glucose. Instead, astrong powder pattern was present which couldnot be identified, either by reference to our localdatabase or to the PDF. A record of the d -spac-ings and relative intensities was kept for futurereference. Within a few months the same un-known pattern had appeared in four unrelatedstreet seizures. In one seizure, this pattern oc-curred together with that of glucose monohy-drate, and this led us to consider that glucosemight be forming a complex with sodium chlo-ride. A literature survey revealed a paper pub-lished in 1947, in which the crystal and molecu-lar structures of complexes between sucrose

and sodium chloride and sucrose and sodiumbromide were reported [23].

We attempted a synthesis of such a complexbetween glucose and sodium chloride by mix-ing weighed amounts of glucose monohydrateand sodium chloride in molecular weight ratios

such as 1 : 1, 1 : 2, and 2 : 1. The powders weremixed dry and left to stand in glass tubes.Within two hours each mixture had “caked”into a solid lump. The lumps were analysed byXRD revealing the pattern of the hithertounidentifiable material together with those of either excess glucose monohydrate or excesssodium chloride (Fig. 11).

The final stage of analysis was completedwith the determination of the crystal and molec-ular structure [24]. Crystals belonged to the trig-onal space group P 31 and the empirical formulaproved to be C

6H

12O

6· 1 /

2NaCl· 1 /

2H

2O (the coor-

dination sphere of the sodium ion in the crystalstructure is shown below in Fig. 12).

Paper

Forensic paper examination and analysis isusually associated with ransom notes, threaten-ing letters, anonymous hate mail, and wrap-pings from drug seizures. The examination willmore than likely be a comparison of paperfrom, for example, the ransom note with thatfound in a suspect’s dwelling. XRD or elementalanalysis may be called for, but only after an ini-


Fig. 10. Diffraction patterns of three forms of amphetamine– top – optically active d -am-phetamine sulphate, centre – racemic dl -amphetamine sulphate, and bottom– racemic dl -am-phetamine hydrochloride.



tial examination by botanical or fibres experts.

XRD is used to identify the fillers present in thepaper and it can also yield useful informationabout the percentage crystallinity of the cellu-lose [25]. A paper’s mineral content dependsupon its use and appearance. A cheap copyingpaper usually has either no filler (cellulose only)or a clay mineral such as kaolinite, whereasother more expensive papers have rutile oranatase as fillers.

Miscellaneous

A small company specialized in the produc-tion of light alloy castings. A supply of the alloy

was kept in the factory under lock and key. Onenight the factory was burgled, and the entirestock of alloy stolen—worth a large sum of money. However, the factory had not been bro-ken into; entry had been effected by someonebearing a key. The only key holders in the com-pany were the three directors. The police inter-viewed all the factory employees, and the three

directors were asked to present their keys forexamination. Information on one of the direc-tors was supplied by the other two, both of whom had their reasons for suspecting theircolleague of complicity in the burglary. Forensicexamination of each of the keys revealedminute traces of a white substance on the keybelonging to the director who was under suspi-cion. The substance was analyzed by XRD (Fig.15) and found to be aragonite (a polymorph of calcium carbonate).

The director who was under suspicion wasthen questioned closely by the police and hishome searched. Hidden in his garage was partof a cuttlefish bone which he claimed was anaid for sharpening his budgerigar’s beak. Thiswas actually true, because cuttlefish bone (Fig.13) is sold in pet shops precisely for that pur-pose, but the man had also used the bone tomake an impression of his key for an accom-plice to cut a duplicate. The texture of aragonitein cuttlefish bone is excellent for making finelydetailed impressions of irregularly shaped ob-jects such as keys (Fig. 14). It emerged that theman had personal financial problems, and in

Vol. 19 No. 2 & Vol. 20 No. 1 2003 19

Fig. 11. Powder photographs of NaCl, heroin hydrochloride hydrate with unknown andNaCl, unknown with glucose monohydrate, and glucose monohydrate.

Fig. 12. Molecular structure of the glucose/ sodium chloride complex.



order to raise some money quickly, he had en-listed the help of a third party to carry out theburglary and steal and sell the alloy stock.

Powder diffraction’s versatility is one of itsgreatest attributes. Its ability to analyze mix-tures of inorganic, organic and metallic sub-stances is very useful indeed. A smoulderingobject was pushed through the letterbox of anelderly man’s house. It began to cause the car-pet to smoulder but the man stamped on it,managed to extinguish it, and then called thepolice. Some children found in the vicinity hadin their possession a packet of theatrical smokepellets. XRD analysis of the partially burnt ma-terial from the man’s house and an unburnt pel-let revealed that they were of similar composi-tion, containing potassium chlorate, ammonium

chloride, alpha-lactose monohydrate, and tracesof sodium chloride (Fig. 16). The children, in thepresence of their parents, were questioned bythe police and it transpired that they had beengiven the smoke pellets by an older boy. Thisboy had encouraged them to light the pellet andpush it through the man’s letterbox. The chil-dren were dismissed with a caution but warnedthat further escapades of this sort would resultin them appearing in a Juvenile Court.

Summary

X-ray powder diffraction is a useful and ver-satile analytical tool in any laboratory, let alonea forensic science laboratory. The purpose of this paper is to raise awareness of its useful-ness, in a forensic context, when the sequence


Fig. 13. Cuttlefish bone. Scale shows inches(upper) and centimeters (lower).

Fig. 14. Impression of a door key made in cuttle-fish bone.

Fig. 15. Powder patterns of (a) cuttlefish bone, (b) white substance from the key, and (c)pure aragonite standard.



of analysis can, on occasion, be almost as im-portant as the analysis itself. The preservationof evidence, contact trace evidence, may bevital, so a non-destructive method of analysis isessential.

Specimens from a scene of crime, or from asuspect, are rarely nice, clean, single phase ma-terials—they are mainly multiphase specimens,

and often contaminated. This contaminationmay be regarded by the analyst as a nuisance,but it is nonetheless part of the specimen andmay have considerable significance with regardto the specimen’s location at the scene. If itcomprises a mixture of organic and inorganicmaterials, XRD will provide simultaneous analy-sis regardless.

Powder diffraction is a powerful technique,but it is not the answer to every analytical prob-lem. Its restriction to solid substances and thefact that it is not really a method for trace analy-sis are its main drawbacks. Analysis of forensiccasework specimens requires a careful, wellthought out approach to the analytical se-quence in order to maximize the informationobtainable, before a sample is destroyed inanalysis. For this reason alone, XRD is one of the techniques that should be considered moreas a first line of attack rather than as a last re-sort.

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Vol. 19 No. 2 & Vol. 20 No. 1 2003 21

Fig. 16. Examples of powder diffraction patterns of mixtures of organic and inorganic com-

pounds. Top – the mixture referred to above – potassium chlorate, ammonium chloride, lactosemonohydrate and sodium chloride. Bottom– a street drug mixture– dl -amphetamine sulphate,glucose monohydrate and Epsom Salts (MgSO4· 7H2O).



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xrd in forensic science from rigaku journal

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