Trace evidence analysis (the future of crime scene investigation)
MSc Analytical Chemistry and Instrumentation Analysis SCGS6190/Seminar Presentation “TRACE EVIDENCE ANALYSIS:THE FUTURE OF CRIME SCENE INVESTIGATION” Name: Norashikin bt Othman Matrix Nu. : SGC100014
CONTENTS1. Objectives2. Introduction3. Trace Evidence4. Importance of trace evidence analysis5. Improved Techniques and Technology i. Glass Evidence Analysis ii. Chemical Composition Identification iii. Collecting and analyzing explosives iv. Body Fluids and Fingerprints Detection6. Conclusion7. References
OBJECTIVES To understand the evidential value of trace evidence in crime scene investigation. To explore the new and improved techniques for detecting and distinguishing trace evidence. To recognize the importance of modern analytical instrumentation in forensic science.
INTRODUCTION Forensic science is a scientific approach and application of science to the requirements of law. The scientific approach contributes to bringing the culprit to justice and exonerating the innocent suspect. Forensic science investigations are based on Locard’s exchange principle and Principle of individuality.
INTRODUCTIONLOCARD’S • In every contact between surfaces,EXCHANGE there will be mutual exchange ofPRINCIPLE matters across the contact boundary. PRINCIPLE • Identification or individualization is based on comparison. OF • Two objects may beINDIVIDUALITY indistinguishable but not identical
Victims Physical Evidence Crime Suspect SceneVictims, crime scene and suspect are all connected to one another through physical evidence. Finding of one of the element will bring the discovery of another.
TRACE EVIDENCE Definition: Trace evidence is minute quantities of natural and man-made materials that readily transfer between objects or between people and objects.
THE IMPORTANCE OF TRACE EVIDENCE ANALYSIS Trace evidence provides connection between a person or object to a specific crime scene. The connection is expected to conclude that two samples “could have” shared a common origin. Conventional techniques are often unable to distinguish the unique characteristic of trace evidence for identification and comparison. Forensic science investigation faces challenges in meeting the increasingly rigorous scientific standards and courts expectations.
Improved Techniques and Technology Glass Evidence Analysis Chemical Composition Identification Explosives Collection and Analysis Body Fluids and Fingerprints Detection
1) Glass Evidence Analysis Glass fragments are among the most frequently encountered physical evidence at crime scene (Parker & Peterson, 1972). Conventional methods rely on the comparison of glass physical properties between the known and questioned sample. The difference of refractive indices and densities are utilized in forensic discrimination of glass samples (Buscaglia,1992). Physical properties comparison offer discrimination but unable to provide classification of glass product type. Improved glass manufacturing processes resulting in narrowing the range of refractive indices in modern glass.
1) Glass Evidence Analysis Quantitative elemental analysis enables discrimination between known and question sample and classification of glass type of product use. Three common techniques: i. Flameless Atomic Absorption Spectroscopy (FAAS). ii. Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). iii. Energy Dispersive X-Ray Fluorescence Spectrometry (EDX-XRF)
Parameter FAAS ICP-AES EDX-XRF1.Destructive Yes Yes No2.Level of detection Extremely sensitive Good Good (but varies with element, excitation, matrix)3.Multi-element No Yes Yestechnique4.Sample preparation Intensive Intensive Virtually none5.Automated Yes Yes Possible6.Cost Moderate High Moderate (XRF), High (SEM/EDX)7.Small sample size Extremely small Small to moderate SEM, very small8.Speed of analysis Very slow Rapid Rapid9.Precision Good High Good (but not at low concentration)10.Accuracy High High Good11. Availability in Possible Highly unlikely Possibleforensic laboratory Table 1 Comparison of three common techniques for elemental analysis of forensic glass sample.
1) Glass Evidence Analysis Highly discriminating techniques have been develop by International Forensic Research Institute – analyzing glass elements using inductively couple plasma-mass spectrometry (ICP-MS). ICP-MS combines enhanced sensitivity and multi-element capability. High level of glass analysis enable all types of glass to be distinguish. ICP-MS allows analysis of very small glass fragments.
2) Chemical Compositions Identification Detection of chemical residues on clothing, fingernail, hair and skin samples are important to provide links between suspected sites and possible offender. Conventional analysis attempts to break down the sample into separate chemicals. This results in destroying the sample during the process. Analysis of small sample size is often not precise enough for detection.
2) Chemical Compositions Identification Static secondary ion mass SIMS SAMPLES DETECTION spectrometry (SIMS) is used to distinguish trace chemicals on various Colorants and chemicals materials. on hair sample SIMS identifies chemical composition of the surface Environmental of extremely small trace contaminants evidence sample – 1/10,000 of an inch. Illicit drug on synthetic Static SIMS show real fiber potential as it able to differentiate and identifies specific samples of various Paint physical evidence. Fingernail polish
3) Collecting and Analyzing Explosives Large bombing sites pose problems in collection and identification of small quantities of explosive residue among large amounts of debris. New method of blast debris collection utilize Teflon surface wipes. Advantages of Teflon surface wipes: i. Shred resistant ii. Dry sampling. iii. Applicable for various surfaces. Evidence collected through dry surface wipes is transfer into gas chromatography column.
3) Collecting and Analyzing Explosives The method are simple, inexpensive and can be readily adapted to forensic laboratory. Portable gas chromatographs are commercially available. Dry sampling should be adapted to crime scene of explosion since environmental factors may speed up sample decomposition.
4) Body Fluids and Fingerprints Detection Conventional method for searching for bodily fluids and fingerprints is fluorescence method. Fluorescence method has a drawback where the light emitted is weak compared to the surrounding room light or at the outdoor crime scene. Criminalistics Light-Imaging Unit (CLU) is a multispectral imaging system. CLU utilizes various colors of light to view the substances or structure being examined. CLU allows detection under normal lighting conditions. This technique is five times more sensitive than fluorescing method.
4) Body Fluids and Fingerprints Detection The usage of visible light in CLU allows location and identification of blood evidence on dark surfaces. CLU can detect untreated fingerprints on transparent, dark and multicolor surfaces. CLU have camera’s video-recording features which work like a cam-coder. CLU replacing the fluorescence method for detection of: Semen Stains Blood spatter pattern and trails Fingerprints
CONCLUSION Advances in technologies for detection and distinguishing trace evident hold a great promise for speeding up evidence collection, limiting contamination and easing the analysis. By generating stronger evidence, these more precise forensic tools will benefit every facet of law enforcement. Justice vide forensic may be the order of the future crime scene investigation.
“THANK YOU”“Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent” -Professor Edmond Locard, -
REFERENCES ACP Dr. Yew Chong Hooi (2008). Application of Forensic Science in Criminal Investigation: The way forward. Forensic Laboratory, RMP. Malaysia. Supt. Shaikh Abdul Adzis (2006). Siasatan Forensik: Pengurusan Tempat Kejadian. Forensic Laboratory, RMP. Malaysia. TA. Brettel, JM Butler & JR Almirall (2011). Forensic Science. Journal of Analytical Chemistry. ACS Publications. NIJ Journal. (2003).Without a trace? Advances in Detecting Trace Evidence. J.A Buscaglia (1992). Elemental Analysis of small glass fragments in forensic science. Criminal Justice, Science Department. USA. B. Parker & J.Peterson (1972). Report of the National Institute of Law Enforcement and Criminal Justice, Washington DC. USA.