Presentation on theme: "Forensic Biology Screening Workshop"— Presentation transcript:
1Forensic Biology Screening Workshop Case Processing
2Case Processing Includes: Location and Collection of Evidence Collection TechniquesPreservation of EvidencePackaging and StorageDocumentation-Chain of CustodyCasework Analysis
3Evidence HandlingNo evidence handling guide can address every conceivable scenario nor is this intended to supersede policies and procedures that a laboratory may already have established, but to serve as a general overview of evidence collection and handling. It is designed to supplement instruction provided by your local forensic laboratory.
4Location and Collection of Evidence Physical Evidence - any tangible object that can connect an offender to a crime scene, an offender to a victim, a victim to a crime scene etc.Biological Evidence is physical evidence - but is not always visible to the naked eye
5Sources of Biological Evidence BloodSemenSalivaUrine/FecesHairTeeth/BoneTissueCells
6Location and Collection of Evidence Many body fluids fluoresce using alternate light sourcesLighted magnifiers may assist in locating stainsMicroscopic evaluation can aid in locating small stainsMapping and/or general swabbing techniques can aid in locating body fluid stains
7Contamination - Sample Handling Disposable gloves - powder freePowder can fluoresce and inhibit PCRPerspiration from collector’s handsChange gloves each time a new piece of evidence is handledOne option is to wear double gloves and change the top pair oftenBetween each item of evidenceAfter touching your face, nose, etcMasks (if necessary)Protects evidence from excessive talking, sneezing or coughingEye ProtectionShoe covers / gowns (if necessary)
8Actions to Avoid Touching any areas/items where DNA may exist Touching your face, nose, hair, and mouth when collecting and packaging evidenceSneezing, coughing, excessive talking near evidenceGloves and or masks should be changed if contaminated
9Evidence Collection Proper evidence collection is aimed at: Avoiding contaminationEnsuring safety and health of personnelPreservation of the evidenceI’m going to talk a little about evidence collection because it can apply to you as an analyst and not just crime scene technicians. Some agencies have separate serology and DNA analysts or you may not always do DNA on the evidence you screened. You as a serologist may have to remove samples from a larger item and repackage to send on for DNA analysis.
10Protect the Evidence BIOHAZARD LABELS Prevent Contamination Preserve evidence with proper packagingProper storageUse appropriate labelsBIOHAZARD LABELS
11Evidence You should: Clean utensils appropriately Use disposables when you canPackage samples separatelyAir dry samples PRIOR to packagingKeep reference samples separate from question samplesUse distilled waterAliquot water if possible
12Evidence You should NOT: Allow contact between drying items Expose items to heat/humidityContaminate your waterUse too much waterUse staplesPackage in plasticUNLESS ITEMS ARE DRYBetter to use paper bags or envelopes if not fully dry to prevent mold / bacterial growthIf packaged in plastic, you can also put a desiccant in the bag to prevent moisture buildup.
13Collection of Biological Evidence Use disposable tools if possibleScalpels, tweezers, scissors, spatulasClean non-disposable tools prior to the collection of each itemIf disposable instruments are not used:Clean with 10% bleach solutionRinse with sterile water or alcoholThoroughly dryCleaning should be done prior to use on each sampleCDC recommends making bleach fresh daily – they have spray bottles that combine as you spray
14Collection of Sharp Objects For safety reasons package evidence such as knives in small cardboard boxes or other rigid containerPackage items to limit movement within the containerAlthough this mostly applies to a crime scene technician, you should know that is the proper packaging. I had a knife one time that came in a paper bag – the knife was folded up (pocket knife) so that no sharp edges were out. Upon examination, I could not close the knife back up, it was very rusted. To avoid injury to myself – I left it open and repackaged it into a cardboard box.
15DocumentationNever collect evidence without documenting the location, conditions, etc firstSketches, photographs, detailed notes
16Collection Techniques CuttingsRemove with sterile or clean cutting deviceWet absorptionSterile swab, gauze or threads lightly moistened with deionized waterConcentrate stain in a localized areaAir dryMay follow with a dry swab to ensure thorough collectionScrapingClean utensil or razorScrape into clean paperFold and packageIt may also be a good idea to collect a control swab. A control swab is a swab taken from an area away from the stained area and serves as a substrate control in the DNA process. It ensures that any results that are obtained are from the stain itself and not the item.
17General Sample Collection Package each stain or swab separatelyDO NOT combine stainsLabel multiple swabs from the same stain accordingly
18Hard Smooth SurfacesImmobile Objects- Car doors, window ledges, tile floors, etcCollect onto a sterile cotton swabScrape onto paper using a sterile scalpelCollect a controlPackage separately
19Soft Porous Surfaces Wood, carpeting, upholstery Cut the stain from the objectCollect a controlPackage separately
20Proper Seals Use tamper resistant tape DO NOT seal evidence with StaplesRisk of injury and sample contamination when handling or unpackagingGluePaper clipsScotch tapeThe seal should be marked with your initials or other appropriate identifier
21Evidence Handling The fewer people who handle evidence, the better Decreases chance of contaminationAssists in court admissibility hearing
22Biological Evidence Storage/Transportation Many laboratory systems store dried biological evidence at room temperatureItems which have body fluids on hard smooth surfaces such as metal or glass should be stored at room temperature. This type of substrate tends to ‘sweat’ when taken out of the freezer/refrigerator which could cause the body fluid to ‘sweat’ off onto the packaging.The degradation of body fluids is retarded when stored frozen, however studies have shown that under appropriate conditions room temperature is okay
23Chain of CustodyA record of individuals who have had PHYSICAL possession of the evidenceCritical in maintaining the integrity of the evidenceIf DNA analysis results in a foreign DNA type, it may be necessary to identify persons who handled the evidence
24Chain of Custody Components Identifiers that describe the evidence at the time it was foundLocationPositionDate/Time of CollectionPackaging/Sealing information
25Evidence Documentation Examine package for seals, tamperingMark evidence according to your lab policyMay include case number, exhibit number, date, initialsNote:Conditions (Seals)For Example: One sealed brown paper bag (sbpg)May abbreviate in your notes as long as it is acceptable per your SOPs.
26Evidence Documentation Open evidence with scissors / knifeTry not to cut through existing seals, if possibleIf this is not possible, it is advisable to document this in the case fileDocument the package contentsIf there are multiple layers of packaging, all should be documented and mark appropriatelyWhen possible, mark the evidence with appropriate identifierYou may be asked in court to identify an item and point out your identifiers. For example, I always try to mark clothing evidence by the manufacturer tag so I can find it quickly. You can also write in your notes where you marked the evidence.
27Evidence Documentation Analyst notes should be sufficient so that the item of evidence can be identified at a later timeInterviewsTestimonyThe description should contain sufficient detailA shirt may be described as follows;red button up long sleeve shirt, with a tear on the front right arm wearing. Several stained areas visible on the front left side wearing. One button missing from front pocket.Digital images will assist in item descriptions, save time and enhance the case fileBest to more descriptive if you can. Something may seem inconsequential to you at the time of analysis but further along in the case it may become important. You also may not see the case file for years before it goes to court. Also take pictures when possible. There is no right or wrong way, you just need to write what YOU need and feel is necessary for the item.
28Evidence Screening Prior to screening Remove hairs and debris to debris foldPossible evidence for later analysisDocument in notes
29Blood Looking for blood: Perform visual exam May use a flashlight, illuminated magnifier or microscopeMark stained areasBlood appears different on different substratesNot always redEnvironmental factors can play role – degraded, old may look different
30BloodTest marked stains, as appropriate – indicate result on item and notesMay choose to take a digital image and mark those areas tested on the imageIf all marked stains result in negative results, analyst may use mapping or general swabbing techniqueSection off itemTake general swabbings from each sectionTest all general swabbingsIf any stain is POSITIVEDocument and remove portion for DNA testingPicture, diagramBest to take digital pictures of the item – if no camera is available then you should either draw a diagram or be very descriptive in your notes about where the stain was found.
31Dried Small Blood Spatters Collect with cotton swabCollect controlPackage separately
32Packaging of Trace Evidence Package in paper; DO NOT use plasticEvidence can stick to the plastic packaging from staticCollect so that you minimize loss or contaminationHairsLoose FibersPaint ChipsSoilGunshot ResidueSome laboratory procedures state that trace evidence should not be removed from the original item unless necessary because they leave it for the trace unit to collect.
33Packaging Label each item with a unique identifier Department record numberUnique item numberCollector’s initialsDate/TimeDescriptionPlace evidence into new paper bags, not plastic bags to prevent degradation
35Semen ALS Screening tool Semen visualized using nm wavelength with orange safety gogglesPerform in dark roomMark areas of fluorescenceSemen fluoresces due topseudomonis fluorescens – bacteria contain fluorophoresflavinsFluorophores excited by energy source (light) emit light energy and are visibleSome agencies perform ALS exam even on swabs – per analyst discretion or your lab policies.
36Sexual Assault Kits Optional ALS exam Screen swabs with Acid Phosphatase testDo microscopic exam on the swabsEven if NEGATIVE - possible breakdown of proteins by body, sperm may surviveOral swabsOral assaults not always reportedDon’t treat as a standard until tested for semenTest swabs per lab policy – some do all swabs for AP. MICRO exam is also per lab policy – some do micro exam on ½ the number of swabs. May differ between labs.Oral assault not always reported – sensitive, embarassing
37Sexual Assault KitsIf Acid Phosphatase POSITIVE and Microscopic exam NEGATIVEPerform Prostate Specific Antigen P30 testCauses of Acid Phosphatase POSITIVE and Microscopic exam NEGATIVEVasectomizedLow sperm countAspermicNo sex occurredFalse positive Acid Phosphatase test
38Sexual Assault KitsCauses of Acid Phosphatase NEGATIVE and Microscopic exam POSITIVEBreakdown of Acid Phosphatase (water soluble)Environmental factorsHeatHumiditybacteriaTime
39Sexual Assault Kits Juvenile sexual assaults Assailants may use saliva as lubricant on juvenilesMay want to perform amylase test on swabs (not oral)Some labs send the samples DNA (no amylase testAnalyst discretion on what is a juvenile. May need to use case information to make this determination.
40Semen Exam for semen on evidence (not swabs) Perform visual exam and mark visual stainsPerform exam with ALS – Alternate Light Source
41SemenTake representative cuttings from marked areas – visible and fluorescent stainsTest Acid Phosphatase + stains for Microscopic exam or Prostate Specific Antigen P30Panties – may want to perform Microscopic exam even if Acid Phosphatase NEGATIVE (like swabs)Depending on case scenario can perform Microscopic exam on Acid Phosphatase NEGATIVE samplesBody breaks down water soluble proteinsSemen stain on cloth – snapshot in time, unless environmental factors (humidity, etc).Document and remove positive areas for DNA testingOld cases, panties or samples that may have been exposed to environmental factors – even if AP is NEG, MICRO may still be POS due to sperm ability to survive on stains longer than water soluble proteins AP and P30. This is case dependent. It should be done on panties – follow lab policy
43Sexual Assault Cases Important to know previous sexual encounters Consensual partnersNeed to request elimination standard from consensual partnersUsed to determine if evidence came from victim, suspect or someone elseIt is very important to have good open communication with the detective on a case. They don’t always think of everything we do.
44Saliva Evidence Items of Interest Masks (robberies) Bitemarks Stamps and Envelopes
45SalivaMost common cases: Burglaries, juvenile sex assaults, assaults (bite marks)Mark visual stainsScreen with ALSMark areas of fluorescenceTake representative cuttings or swabbings to extract for amylase test of choicePositive areas – document and remove for DNA testingMay just send straight on for DNA testing so as not to consume any sample for amylase test.The wavelength used and goggle color may vary – you should try a variety of combinations to determine which you like best. Some labs report using orange goggles and my lab policy states to use yellow or clear, but you can still see the stain using orange.
46Multi-Section CasesMany items need to go through other sections of the labCommon requests:Latent PrintsTrace / MicroanalysisFirearms
47Multi-Section Cases Latent Prints: Important to talk to detective to find out what they are looking forIf need both serology AND latent prints you should do serology FIRST if possibleYou can have latent examiner present if you are worried about destroying printsIf availableLatent chemicals, while are not supposed to affect DNA, may inhibit the tests. They also make it hard to see stains on items. Latents examiners, if available, may be present during initial exam – can bring magnifying glass and lend expertise on whether visible prints are viable. Maybe tell you what areas to stay away from if possible during your testing.
48Multi-Section Cases Trace / Microanalysis: Talk to detective about what they are looking for on evidenceIf microanalysis is necessary – should be swept first BEFORE you open for testingPrevents transfer from you to evidence (hair, fibers) or loss of trace evidenceSweeping is a process that is used to remove all trace evidence from an item into a debris fold.
49Multi-Section Cases Firearms: Serology tests don’t typically interfere with firearms analysisTalk to detectiveYou should have evidence first to prevent contamination if possibleIf firearms examiners handle before you – should wear glovesSerial # restoration uses chemicals which may affect stains
50Multi-Section Cases Firearms: Sometimes cases need “touch” evidence on guns, bulletsImportant that the evidence is protectedSwab first for DNA before handled by other sections – if possible
51Multi-Section Cases Storage: Be aware of storage policies for other sectionsDon’t store blood on glass or guns in freezer
52Multi-Section CasesImportant to know limitations and functions of other sectionsTalk with detectivesEX. Sometimes they have to pick – latent print analysis or serologyMake sure detectives understand what each section can do so they can make the best decision for the case
53Reference Samples Blood Blood transfusions Buccal Swabs/Saliva ClothingLast resort secondary standardOther Secondary StandardsToothbrush, hairbrush, glasses, etc.Other standardsAll persons who had access to a crime scene should be documentedMay be necessary to collect samples from these individuals
54BurglaryAll persons who had access to a crime scene should be documentedMay be necessary to collect samples from these individuals
55Hair Evidence Types of Testing Available Comparative Physical and chemical characteristicsHuman originDNANuclear (STR DNA Analysis ) - with root only!MtDNA - if no root
56TOUCH EVIDENCEEpithelial cells that have been transferred from the person to the evidence via “touching”These samples tend to have low amounts of DNAWould expect body fluid stains to have more DNA than touch evidenceBody fluid comparison:Undiluted semen (with sperm) stain > blood stainBoth blood and semen > saliva stainBody fluids > wear area stain (armpits, collar of a shirt)Mention shedders v. non sheddersDiscuss that there are a lot of variations of stains and varying conditions. You can never know 100% what stain is going to have more DNA than another stain.