Forensic Science 101 A quick overview of some basic principles & issues

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1 SCIENCE Forensic Science 101 A quick overview of some basic principles & issues Elaine M. Pagliaro, MS, JD knowledge about or study of the natural world based on facts learned through experiments and observation Pure science (Research) Applied science (Cole s Work science) Application of the principles and procedures of science to matters of the law Forensic Science General focus of forensic testing Identification Individualization Association Reconstruction American Association of Forensic Sciences Criminalistics Forensic Biology / DNA Drug testing Chemistry / Trace Fingerprints Firearms other Toxicology Digital & Multimedia Engineering Pathology/Biology Odontology Anthropology Jurisprudence General Crime scene Forensic nursing reconstruction PHYSICAL EVIDENCE- What we do 1

2 Forensics by type of Analysis Analytical Science Biology Serology DNA Trace evidence Chemistry Toxicology Drug chemistry Trace evidence Physics/Engineering Trajectories Flight Pattern Analysis Comparison Individualization ( ID ) -Fingerprints -Firearms -Pattern match Reconstruction Issue #1: Recognition of Evidence for Testing Evidence Recognition is a Key Step in the Forensic Process Requires proper training of analysts & scene personnel Requires a scientific v. technician view Where is the evidence? Identification Classification Forensic Process Individualization Is the Identity of the sample known? YES NO Determine class & individual Perform characteristics screening/presumptive Determine natural variation tests Compare class characteristics Perform confirmatory tests Are there individual Does origin need to be characteristics? determined? Analytical Forensics Biology Serology DNA Chemistry Toxicology Drug chemistry Trace evidence NO YES YES NO END Compare Individual characteristics Search Database END 2

3 Chemical Analysis Example Drug / Toxicology Critical analyses Key chemicals in today s crimes Best Places for Toxi Testing Blood most useful tells what is going on at the time of death. Urine Easily obtained Urine can t determine whether a drug was exerting any effect at time it was collected. Stomach Contents Still no correlation between effects at time it was collected but will determine if in the body Liver important in metabolism (destruction) of undesirables in the body. Many drugs concentrate in the liver; no signs may be in the blood but the liver will reveal if a toxin is present. Amounts in liver determine hours before death. Amount in bile determines past 3-4 days of exposure Hair questions about accuracy and reproducibility. Overreach in testimony Drug Testing = Similar techniques Common Drugs Cocaine Hydrochloride (salt form) Heroin Categorized by physiological and psychological effects. Can affect structure or function of tissues via chemical reactions 75% of evidence analyzed in crime labs is drug-related Pharmaceutical companies send samples of new drugs to the FBI to be categorized for future comparisons Toxicology expert relates addiction to effects on individual and behaviors (mitigating circumstances) Classification of Drugs Opiates/Narcotics* morphine, heroin, codeine, fentanyl Both physically and psychologically addictive Stimulants amphetamines, cocaine, nicotine Psychologically addictive Depressants Barbiturates, Ethanol Physically and psychologically addictive Hallucinogens LSD,PCP, MDMA (Ecstasy), Mescaline, Marijuana, mushrooms (psilocybin) Most no dependence WEBINAR 4 TOXICOLOGY ESSENTIALS: EMPHASIS OPIOIDS 3

4 Common Testing Procedures 1. Color Tests a reagent is added to the substance to be tested and a color change will indicate the presence of the suspected chemical. - CHEAP, EASY, and QUICK - False Positives 2. Immunoassays Antigen-antibody reaction substance being sought is the antigen-testing reagent is the antibody. - An antibody will react only with antigens and ignores all other chemicals 3.Chromatography Separates compounds according to size, shapes, and chemical properties will determine class of compounds - can be used to separate a large mixed sample for further analysis 4. Spectroscopy different compounds absorb and reflect light (energy) differently identifies the drug & its concentration 5. Mass Spectrometry (MS) high energy bombards the sample and breaks it into tiny fragments. They are passed through a magnetic field and separated by molecular weight Produces the same pattern can be used to ID. Methods of Detection UV-VIS Spectrum Chromatography a. thin-layer chromatography (TLC) b. gas chromatography (GC) c. high performance liquid chromatography (HPLC) Spectroscopy - Instrumental a. UV light d. X-ray b. visible light e. infrared c. Raman Example IR Spectrum = peaks used to identify drug 4

5 Methods of Detection Mass Spec 5. Mass Spectroscopy - Instrumental 6. Immunoassay Disc or instrumental. EMIT Immunoassay of drugs Questions about ANALYSIS Procedures are generally standard Some drugs / tissues require method development & validation Look at basic theory of testing - What are the procedures used? - What are the limitations of the testing? - What are the advantages of the testing? - How reliable are the findings? - Quality control -Examiner Chemical Analysis: Trace Evidence Materials in small amounts or quantities are linked to a possible source. Examples Paint Unknown Chemicals Fibers Metals GSR Hairs Trace Evidence Methods Sequence Physical characteristics Microscopical properties Optical properties Instrumental analysis GC-MS SEM IR Raman Other 5

6 Trace Evidence: General Considerations Individualization is not possible with most trace evidence Potential sources may be identified Provides association (linkage) to individuals, things or places Usually cannot associate trace evidence with a time of deposit Instrumental analysis to detect residues Academic Research on classes of materials, e.g. nail polish Instrumental analysis will confirm the presence of an explosive material. Instrumental Methods to Examine Residues Contamination by metals or other compounds could mask or add additional elements. Scanning Electron Microscopy ICP Trace Example: Paint comparison What is the significance of this + comparison? (Paint study 2016 with database comparison) Physical & microscopical examination & comparison Instrumental exam of each layer FTIR - composition SEM morphology & elemental composition What is the significance of a positive Trace comparison? Qualitative statements Similar Not similar Inconclusive No number can be assigned to the uniqueness by this standard Quantitative statements (chemometrics) Identifying variables that allow discrimination based on observations Determination of the randomness of a positive comparison by calculating variations 6

7 Odor from a particular source? Searching for trace evidence Max. Control Concentratio Maximum GC-MS DATA n (ppt) (ppt) Earliest latest Also detected in Carbon 1 83 tetrachloride >18,000 Human Human, Toluene >18,000 2 deer, dog Ethane, 1,1,2- trichloro- 1,2,2- trifluoro ,932 Human, dog Tetrachloroe thene >18,000 Deer, dog Naphthalene >18,000 Dog Trichloromo nofluoromet hane >18,000 Deer, dog Dimethyl ,932 disulfide 1,4 dimethyl >18,000 Human, dog benzene Human, 9 Benzene >18,000 deer, dog Dichlorodiflu oromethane n.d ,932 Deer, dog 1,2 dimethyl >18,000 benzene 12 Chloroform ,932 Dog Chloroform & human decomp identification? Chemical Testing What is found v. what is the significance of the finding What = scientific fact Significance = opinion 7

8 Test Issues Reproducible results? Experimental Design Other sources Over-reaching testimony Limited experience within community Academic v. forensic experience Trace Evidence: Hair analysis Methods Microscopical comparison Mitochondrial examination Determination: Origin of Hair Growth phase Forcible removal Possible source Hair Analysis Remember that some of this information may be key to the case and NOT controversial Animal hair identification Exclusionary value Associate mtdna finding Species Identification of Animal Hairs Biogeographical ( Racial ) Identification of Human Hairs Rabbit Fox Seal Chinchilla CHARACTERISTIC -Medullary index -Cuticle pattern -Medulaa pattern -Physical appearance -Color -Taper -Root shape -other African ( Negroid ) European ( Caucasian ) Asian ( Mongoloid ) 8

9 Means of Removal But mtdna testing is not individualizing Forcibly Removed or Naturally Shed mtdna testing without microscopical exam and comparison can provide a false inclusion since all members of the maternal line will have the same mtdna Case example murder / attempted murder. BIOLOGICAL EVIDENCE DNA analysis changed the way we do Biology Screening Tests are still essential in the age of DNA! ID & Confirmatory tests Understand the limits Screening Confirmatory Not always all they are cracked up to be Y-DNA detection Human saliva by RSID* * Detects human amylase. Also reacts with human feces and milk. Human saliva detected 1.Yellow and brownish Stains noted in crotch area of the child s panties 2.Tests for the presence of human saliva were positive In spite of brownish stains in crotch, no tests for feces were done 9

10 DNA may include accused but Capital Case What material is giving the DNA profile of accused in the mixture detected? How long has it been there? DNA results may match But Patterns may be the Critical evidence! Torn sleeve swabbed & DNA unit result cannot exclude defendant Expert stated: Transferred during struggle between victim and defendant when the sleeve was torn. Testimony Issues Pattern Evidence Pattern Evidence Examination Identify pattern Determine class characteristics Determine individual characteristics Compare to known Source or cause Experimentation often necessary to support conclusion 10

11 Pattern Evidence General Issues PATTERNS OF DEPOSIT DEVELOPED BY CHEMICAL TESTING: WHAT WAS THE DISTANCE TO THE TARGET? Basis of conclusion Uniqueness of sample Sample handling Methodology Reproducibility Range of conclusion, where applicable Bias Determination of source Choice of experimental design Influence of case information Untreated Test for Nitrites Test for Lead Fingerprint Pattern Evidence Process Classification & Individualization Examination of general pattern & characteristics Identification of individualizing characteristics (minutiae) Evaluation of the individual characteristics in relation to each other Comparison Comparison to known patterns Search of database Conduct experiments to confirm conclusions, as applicable Fingerprint Comparison Issues Methodology Latent fingerprint development issues Latent fingerprint completeness Quality of the resulting image Interpretation of missing portions by examiner 63 Challenges in Traditional FP Analysis Units Traditional learning method v. advanced education No scientific background to relate to scientific questions & experiments Terminology of science is unfamiliar to traditional examiner Cognitive bias Limited knowledge of why development methods work and sequential processes effects Lack of statistical expression of significance of comparison How effective are those arguments? 11

12 Questions to consider in pattern evidence interpretation Pattern itself How was the pattern deposited? When was the pattern deposited? Can the deposit be linked to the activity or incident? Examiner Extent of training and experience Knowledge of limitations of the testing Availability & use of statistical analysis programs to assess significance Science in the service of justice Objective observation Open- minded evaluation Unbiased conclusions Clear testimony 12