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Isotopes and Forensic Science

Isotopes and Forensic Science. University of Lincoln presentation. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License. Overview. The forensic perspective The atom Radioactive and stable isotopes – properties and measurement

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Isotopes and Forensic Science

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  1. Isotopes and Forensic Science University of Lincoln presentation This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  2. Overview • The forensic perspective • The atom • Radioactive and stable isotopes – properties and measurement • Dating techniques • Stable isotope applications • Nuclear forensic science – atomic detectives This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  3. 1. The Forensic Perspective This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  4. “Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only his fingerprints or foot prints, but his hair, the fibres from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these and MORE, bear mute witness against him” Prof Edmond Locard (1877-1966) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  5. The Locard Principle of Exchange: “When objects come into contact there is a transfer of particles”……. This is a Principle that Scientists have struggled to exploit But Improvements in technology have brought new concerns… “Physical evidence cannot be wrong……..only interpretation can err” This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  6. Modern analytical techniques can now identify compounds containing <1ng (1 x 10-9g) of substance Increasing potential for CONTAMINATION and MIS-INTERPRETATION Recent high profile cases where: Evidence was mishandled Amount of evidence caused concern Results may have been misinterpreted Trace Analysis This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  7. Spanish Euros average 335μg cocaine per note! £15M of drug- contaminated notes are destroyed in UK each year Cotton / linen matrix of banknotes is ideal for trapping crystals 99% of London banknotes are contaminated with Cocaine Drug Contaminated Banknotes: This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  8. 2. The Atom This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  9. Example: Neon-20 • Positively charged nucleus consisting of protons (Z) and neutrons (N) • Electrons (e) occupy distinct energy levels around the nucleus • Atomic Mass = Z + N • Atomic Number = Z • For Neon-20, we have Z = N = 10, written as: Electron Nucleus This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  10. U Henri Becquerel Discovered Radioactivity in 1896 Placed pitchblende on a photographic plate and observed…. Henri Becquerel Nobel Prize (Physics) 1903 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  11. Marie and Pierre Curie • 1896 discovery of Radium and Polonium • 1903 PhD and Nobel Prize for Physics • 1903 isolation of Radium • 1908 Nobel Prize for Chemistry This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  12. Types of radioactive decay: alpha, α(Z > 83) Alphaparticle (Helium nucleus) Daughter nucleus Parent nucleus This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  13. Types of radioactive decay: beta, β- (N/Z too large) Converting N to P Beta particle (Negatron) Daughter nucleus Parent nucleus This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  14. Types of radioactive decay: beta, β+ (N/Z too small) Converting N to P Beta particle (Positron) Daughter nucleus Parent nucleus This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  15. Parent nucleus Daughter nucleus Gamma rays Types of radioactive decay: gamma, γ (excited nucleus) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  16. Radioactive Decay Growth/Decay curves for radioactive elements This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  17. Half-Life This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  18. α-decay Z: -2 N: -4 β-decay Z: +1 N: +/-0 Decay series of short lived nuclides This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  19. 3. Isotopes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  20. Evidence: 3 decay series end in Lead Inability to separate ‘elements’ in the 3 decay series Atomic Mass values not always integers (e.g. Ne = 20.2) 1913 Soddy proposed existence of ISOTOPES Definition: Atoms of the same elements with different Atomic Mass Frederick Soddy Frederick Soddy Nobel Prize (Chemistry) 1921 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  21. Isotope Ratio MS Magnetic sector Ion Source Faraday cups Detection system Detection of Isotopes Existence of ISOTOPES confirmed by Aston using the first mass spectrometer in 1919. Analysis of Neon gas achieved separation of 3 stable isotopes: 90.9% 0.3% 8.8% This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  22. Chart of the Nuclides • A nuclide = an isotope • Narrow band of stability • For stability, N/P ratio rises with mass • All nuclides outside the band and with Z > 83 are radioactive • Elements can have from 0 – 10 stable Isotopes β- emission β+ emission This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  23. 4. Dating Techniques This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  24. The Clocks in the Rocks • In the beginning was the BIG BANG • Solar system / earth condensed from dust and gas • Radioactive elements decay to daughters (Parent : Daughter ratio changes with time) • With half-life can calculate the age of the earth This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  25. Dating with Isotopes Process: • Select suitable isotope • Clearly the 14C - 14N system is useless ….. beyond 40,000 years • The 87Rb – 87Sr system is fine for 60M to 400G years! Parent C-14 Daughter N-14 Parent Rb-87 Daughter Sr-87 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  26. Process: • Ideally the crystals in the rock should contain no Sr (eg: Mica in Granite) • All subsequent Sr arises from Rb decay • Earliest rocks on Earth are 4G years old • On melt, the clock is reset when new igneous rock is formed This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  27. Strontium Dating – the Forensic Application • Sr has 4 stable isotopes • As a result of 87Rb decay, 87Sr levels will rise with time • 87Sr / 86Sr is highest in oldest rock • Sr has similar chemistry to Calcium and ends up in BONE 0.715 ---- 0.730 ---- 88Sr 7% 87Sr 10% 86Sr 82% 84Sr 1% 87Sr / 86Sr ratios: 0.703 in young rock 0.750 in oldest rock This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  28. Strontium Dating – Tracing Adam • Sept 2001, torso of 5 yr old boy recovered from Thames • Suspected ‘muti’ style ritual killing • Gut contents suggested poisoning and UK as place of murder • Bone 87Sr/86Sr was high – Pre-Cambrian levels • Police search for relatives in rural area between Benin City and Ibadan, Nigeria…arrest made in Dec 2003 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  29. Carbon Dating Cosmic radiation Carbon-14 Nitrogen-14 Neutron capture • 14C half life = 5730 yrs • Excellent for dating organic material from 0-40,000 yrs* Why is there any 14C left, & how does it work? • Assume 14C is continually being produced at the same rate. • Whilst alive, 14C levels remain constant. Only on death does the level start to drop • However, calibration is needed to get accurate dates 14C is absorbed along with 12C and 13C into the tissue of living organisms in a fairly constant ratio Soil When an organism dies 14C converts back to 14N by beta decay Beta decay Nitrogen-14 Carbon-14 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  30. Carbon-14 and Tree Rings • Bristlecone Pine allows calibration back 7000yrs …. …..HOW? • Calibration shows that 14C production is variable…... WHY? • Variation in Solar flux • Decreases caused by burning fossil fuels • Increases caused by A-bombs This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  31. Piltdown Man - a fake! Turin Shroud - mediaeval (1260 to 1390AD) Zoroastrian Mummy – post A-bomb era Carbon Dating – the Forensic Application This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  32. 5. Stable Isotopes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  33. Lead in Human Teeth Data from Australian Citizens –Tooth Enamel Origin 206Pb/204Pb Australia 16.56 CIS 17.98 Balkans 18.23 UK 16.92 Gulson et al J. Forensic Science 42, 787-791. • Pb has 4 stable isotopes • Pb isotope ratios in our bodies reflect that of the environment: –Enamel - Pb content set in childhood –Dentine - 1% of Pb exchanges per annum –Jaw bone - 10% exchanges per annum Isotope Origin 208Pb 232Th 207Pb 235U 206Pb 238U 204Pb Big Bang Ratio 206Pb/204Pb in geology: Varies according to origin / age ….. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  34. Isotope Fractionation • Stable Carbon Isotopes: • 12C – 98.89% • 13C - 1.11% • Light isotope: • - forms weaker bonds • is more reactive • as CO2 will diffuse faster • The Chemistry of elements is largely determined by its electronic structure • But differences in mass give rise to kinetic and equilibrium effects RESULT: In photosynthesis some plants discriminate AGAINST13C This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  35. Fractionation via Photosynthesis Examples of C3 Plants: Wheat, Barley, Rice, Oats, Sugar Beet …in fact most nutritionally important plants. Examples of C4 Plants: Sugar Cane and Maize. • 2 major photosynthesis pathways: C3 and C4 plants • C3 discriminate much more than C4 plants RESULTS: CO2 (air) = 1.11% 13C C4 plants = 1.10% 13C C3 plants = 1.08% 13C This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  36. Isotope Ratio MS Magnetic sector Ion Source Faraday cups Detection system Measuring C-13 Levels Species Mass 12C16O2 44 13C16O2 45 • Use Isotope Ratio Mass Spectrometry (IRMS) • Very Precise (+/- 0.0005% 13C) • Key Features: • - Measured as CO2 • Dual Inlet • Triple Collector • Measured v. Ref Gas This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  37. Stable Isotopes – Some Forensic Applications Food / Drink adulteration • Malt is expensive • Sugar is cheap! • Both ferment to produce alcohol • Temptation to adulterate! Fermentation: Sugars C2H5OH Sugar Source δ13C Malt (UK) -25.9 Maize -13.0 Sugar Cane -12.0 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  38. Adulteration: Alcoholic Beverages Wines Wine Bootleg Port/Brandy Whisky Cz Bootleg Whisky Malt Blended Scotch B’bon Beer German UK Sugars Malt Maize/Cane -30 -20 -10 Δ13C per mil v. PDB This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  39. Adulteration: Maple Syrup Same approach has been used for honey, fruit juice, olive oil and maple syrup By combining 2H:1H ratios with 13C:12C ratios we can achieve greater DISCRIMINATION Cane -10 δ13C -20 Maple Beet ‘Maple’ Adulterated syrup shown to contain 40% Beet sugar -30 90 100 110 2H ppm Martin et al (1996) J Agric Food Chem, 44, 3206. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  40. Nakamura et al (1992) Biomed Mass Spectrom, 8, 390. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  41. δ13C -18 USA Travelling German Business Men -20 -18 Japan -20 1 2 3 4 Weeks Nakamura et al Biomed Mass Spectrom, 8, 390. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  42. It is important to establish: Geographical source Evidence of ‘batch’ synthesis of Heroin Sources of Heroin Morphine Heroin This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  43. Geographical Source of Heroin From: Besacier et al (1997)J Forensic Science, 42, 429 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  44. 6. Nuclear Forensic Science – the Atomic Detectives This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  45. Trafficking Nuclear Materials This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  46. Smuggled Plutonium – can identify the reactor type in which the fuel was originally radiated and the type of plant where the material was subsequently reprocessed In 1997, two pieces of stainless steel contaminated with alpha-emitters were found in a scrap metal yard in Germany. Source was identified as a fast-breeder reactor in Obninsk, Russia Man-made Radioactive Isotopes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  47. The isotopic composition of plutonium can indicate INTENT In 1994, a small lead cylinder discovered in a garage in Tengen on the Swiss-German border was found to contain plutonium metal, isotopically enriched to 99.7% Weapons-grade Pu-239 Weapons-grade Plutonium This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  48. Preserving the conventional chain of evidence whilst dealing with radioactive samples can be problematic For example – lifting fingerprints and swiping for radioactive contamination cannot both be carried out The first ever radioactive fingerprint has recently been identified on an object contaminated with alpha-emitting isotopes Radioactive Fingerprints This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  49. Conclusions • ‘Crime is a complex interaction of people and things at different points in time and space’ (RE Stockdale, Science Against Crime). • Isotopes provide a powerful and new approach for investigating diverse crimes. • Need for careful standardisation / calibration • Enormous research and development opportunities. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

  50. Acknowledgements • JISC • HEA • Centre for Educational Research and Development • School of natural and applied sciences • School of Journalism • SirenFM • http://tango.freedesktop.org This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

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