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

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Presentation on theme: "This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Isotopes and Forensic Science University."— Presentation transcript:

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

2 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Overview 1.The forensic perspective 2.The atom 3.Radioactive and stable isotopes – properties and measurement 4.Dating techniques 5.Stable isotope applications 6.Nuclear forensic science – atomic detectives

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

4 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Prof Edmond Locard ( ) 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

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

6 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Trace Analysis Modern analytical techniques can now identify compounds containing <1ng (1 x g) 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

7 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Drug Contaminated Banknotes: 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

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

9 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 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: Nucleus Electron

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

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

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

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

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

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

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

17 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Half-Life ParentDaughter / RadiationHalf-Life (Y) 3H3H 3 He + 0 β C 14 N + 0 β Rb 87 Sr + 0 β X Pb 206 Pb + 4 α U 234 Th + 4 α +2 + γ 4.5 X 10 9

18 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License ElementUranium- 238 seriesTh- 232 seriesU-235 series UraniumU *10 9 y U y U *10 8 y ProactiniumPa min Pa y ThoriumTh d Th y Th *10 10 y Th y Th h Th d ActiniumAc h Ac y RadiumRa y Ra y Ra d Ra d Francium RadonRn d Astatine PoloniumPo min Po s Po d BismuthBi min Bi d LeadPb min Pb y Pb-206 stable Pb-208 stable Pb-207 stable α -decay Z: -2 N: -4 β -decay Z: +1 N: +/-0 Decay series of short lived nuclides

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

20 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Frederick Soddy 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 Nobel Prize (Chemistry) 1921

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

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

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

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

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

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

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

28 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 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 87 Sr/ 86 Sr was high – Pre- Cambrian levels Police search for relatives in rural area between Benin City and Ibadan, Nigeria…arrest made in Dec 2003

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

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

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

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

33 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Lead in Human Teeth 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 208 Pb 232 Th 207 Pb 235 U 206 Pb 238 U 204 Pb Big Bang Ratio 206 Pb/ 204 Pb in geology: Varies according to origin / age ….. Data from Australian Citizens –Tooth Enamel Origin 206 Pb/ 204 Pb Australia CIS Balkans UK Gulson et al J. Forensic Science 42,

34 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Isotope Fractionation The Chemistry of elements is largely determined by its electronic structure But differences in mass give rise to kinetic and equilibrium effects Stable Carbon Isotopes: 12 C – 98.89% 13 C % Light isotope: - forms weaker bonds - is more reactive - as CO 2 will diffuse faster RESULT: In photosynthesis some plants discriminate AGAINST 13 C

35 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Fractionation via Photosynthesis 2 major photosynthesis pathways: C 3 and C 4 plants C 3 discriminate much more than C 4 plants RESULTS: CO 2 (air) = 1.11% 13 C C 4 plants = 1.10% 13 C C 3 plants = 1.08% 13 C Examples of C 3 Plants: Wheat, Barley, Rice, Oats, Sugar Beet …in fact most nutritionally important plants. Examples of C 4 Plants: Sugar Cane and Maize.

36 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Measuring C-13 Levels Use Isotope Ratio Mass Spectrometry (IRMS) Very Precise (+/ % 13 C) Key Features: - Measured as CO 2 - Dual Inlet - Triple Collector - Measured v. Ref Gas Species Mass 12 C 16 O C 16 O 2 45 Ion Source Detection system Faraday cups Magnetic sector Isotope Ratio MS

37 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Stable Isotopes – Some Forensic Applications Food / Drink adulteration Malt is expensive Sugar is cheap! Both ferment to produce alcohol Temptation to adulterate! Fermentation: Sugars C 2 H 5 OH Sugar Source δ 13 C Malt (UK) Maize Sugar Cane -12.0

38 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Adulteration: Alcoholic Beverages Malt Maize/Cane UKGerman MaltBlended ScotchBbon Cz Bootleg WineBootleg Port/Brandy Δ 13 C per mil v. PDB Wines Beer Whisky Sugars

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

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

41 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Travelling German Business Men

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

43 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Geographical Source of Heroin Drug source Heroin δ 13 C Morphine (H-M) Acetyl source Lebanon Lab 1 Lebanon Lab 1 Thailand Lab 2 Turkey Lab 2 Turkey Lab 3 From: Besacier et al (1997)J Forensic Science, 42, 429

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

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

46 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Man-made Radioactive Isotopes 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

47 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Weapons-grade Plutonium 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

48 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Radioactive Fingerprints 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

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

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


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